740 lines
19 KiB
Groff
740 lines
19 KiB
Groff
.\" $NetBSD: libnvmm.3,v 1.27 2020/09/05 07:22:25 maxv Exp $
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.\"
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.\" Copyright (c) 2018-2020 Maxime Villard, m00nbsd.net
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.\" All rights reserved.
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.\"
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.\" This code is part of the NVMM hypervisor.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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.\" AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.Dd February 9, 2020
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.Dt LIBNVMM 3
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.Os
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.Sh NAME
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.Nm libnvmm
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.Nd NetBSD Virtualization API
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.Sh LIBRARY
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.Lb libnvmm
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.Sh SYNOPSIS
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.In nvmm.h
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.Ft int
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.Fn nvmm_init "void"
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.Ft int
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.Fn nvmm_capability "struct nvmm_capability *cap"
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.Ft int
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.Fn nvmm_machine_create "struct nvmm_machine *mach"
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.Ft int
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.Fn nvmm_machine_destroy "struct nvmm_machine *mach"
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.Ft int
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.Fn nvmm_machine_configure "struct nvmm_machine *mach" "uint64_t op" \
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"void *conf"
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.Ft int
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.Fn nvmm_vcpu_create "struct nvmm_machine *mach" "nvmm_cpuid_t cpuid" \
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"struct nvmm_vcpu *vcpu"
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.Ft int
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.Fn nvmm_vcpu_destroy "struct nvmm_machine *mach" "struct nvmm_vcpu *vcpu"
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.Ft int
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.Fn nvmm_vcpu_configure "struct nvmm_machine *mach" "struct nvmm_vcpu *vcpu" \
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"uint64_t op" "void *conf"
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.Ft int
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.Fn nvmm_vcpu_getstate "struct nvmm_machine *mach" "struct nvmm_vcpu *vcpu" \
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"uint64_t flags"
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.Ft int
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.Fn nvmm_vcpu_setstate "struct nvmm_machine *mach" "struct nvmm_vcpu *vcpu" \
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"uint64_t flags"
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.Ft int
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.Fn nvmm_vcpu_inject "struct nvmm_machine *mach" "struct nvmm_vcpu *vcpu"
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.Ft int
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.Fn nvmm_vcpu_run "struct nvmm_machine *mach" "struct nvmm_vcpu *vcpu"
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.Ft int
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.Fn nvmm_hva_map "struct nvmm_machine *mach" "uintptr_t hva" "size_t size"
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.Ft int
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.Fn nvmm_hva_unmap "struct nvmm_machine *mach" "uintptr_t hva" "size_t size"
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.Ft int
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.Fn nvmm_gpa_map "struct nvmm_machine *mach" "uintptr_t hva" "gpaddr_t gpa" \
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"size_t size" "int prot"
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.Ft int
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.Fn nvmm_gpa_unmap "struct nvmm_machine *mach" "uintptr_t hva" "gpaddr_t gpa" \
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"size_t size"
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.Ft int
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.Fn nvmm_gva_to_gpa "struct nvmm_machine *mach" "struct nvmm_vcpu *vcpu" \
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"gvaddr_t gva" "gpaddr_t *gpa" "nvmm_prot_t *prot"
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.Ft int
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.Fn nvmm_gpa_to_hva "struct nvmm_machine *mach" "gpaddr_t gpa" \
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"uintptr_t *hva" "nvmm_prot_t *prot"
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.Ft int
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.Fn nvmm_assist_io "struct nvmm_machine *mach" "struct nvmm_vcpu *vcpu"
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.Ft int
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.Fn nvmm_assist_mem "struct nvmm_machine *mach" "struct nvmm_vcpu *vcpu"
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.Sh DESCRIPTION
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.Nm
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provides a library for emulator software to handle hardware-accelerated virtual
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machines in
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.Nx .
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A virtual machine is described by an opaque structure,
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.Cd nvmm_machine .
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Emulator software should not attempt to modify this structure directly, and
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should use the API provided by
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.Nm
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to manage virtual machines.
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A virtual CPU is described by a public structure,
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.Cd nvmm_vcpu .
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.Pp
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.Fn nvmm_init
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initializes NVMM.
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See
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.Sx NVMM Initialization
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below for details.
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.Pp
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.Fn nvmm_capability
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gets the capabilities of NVMM.
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See
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.Sx NVMM Capability
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below for details.
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.Pp
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.Fn nvmm_machine_create
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creates a virtual machine in the kernel.
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The
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.Fa mach
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structure is initialized, and describes the machine.
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.Pp
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.Fn nvmm_machine_destroy
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destroys the virtual machine described in
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.Fa mach .
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.Pp
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.Fn nvmm_machine_configure
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configures, on the machine
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.Fa mach ,
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the parameter indicated in
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.Fa op .
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.Fa conf
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describes the value of the parameter.
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.Pp
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.Fn nvmm_vcpu_create
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creates a virtual CPU in the machine
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.Fa mach ,
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giving it the CPU id
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.Fa cpuid ,
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and initializes
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.Fa vcpu .
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.Pp
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.Fn nvmm_vcpu_destroy
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destroys the virtual CPU identified by
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.Fa vcpu
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in the machine
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.Fa mach .
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.Pp
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.Fn nvmm_vcpu_configure
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configures, on the VCPU
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.Fa vcpu
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of machine
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.Fa mach ,
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the parameter indicated in
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.Fa op .
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.Fa conf
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describes the value of the parameter.
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.Pp
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.Fn nvmm_vcpu_getstate
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gets the state of the virtual CPU identified by
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.Fa vcpu
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in the machine
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.Fa mach .
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.Fa flags
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is the bitmap of the components that are to be retrieved.
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The components are located in
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.Fa vcpu->state .
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See
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.Sx VCPU State Area
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below for details.
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.Pp
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.Fn nvmm_vcpu_setstate
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sets the state of the virtual CPU identified by
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.Fa vcpu
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in the machine
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.Fa mach .
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.Fa flags
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is the bitmap of the components that are to be set.
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The components are located in
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.Fa vcpu->state .
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See
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.Sx VCPU State Area
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below for details.
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.Pp
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.Fn nvmm_vcpu_inject
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injects into the CPU identified by
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.Fa vcpu
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of the machine
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.Fa mach
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an event described by
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.Fa vcpu->event .
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See
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.Sx Event Injection
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below for details.
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.Pp
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.Fn nvmm_vcpu_run
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runs the CPU identified by
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.Fa vcpu
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in the machine
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.Fa mach ,
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until a VM exit is triggered.
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The
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.Fa vcpu->exit
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structure is filled to indicate the exit reason, and the associated parameters
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if any.
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.Pp
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.Fn nvmm_hva_map
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maps at address
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.Fa hva
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a buffer of size
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.Fa size
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in the calling process' virtual address space.
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This buffer is allowed to be subsequently mapped in a virtual machine.
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.Pp
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.Fn nvmm_hva_unmap
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unmaps the buffer of size
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.Fa size
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at address
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.Fa hva
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from the calling process' virtual address space.
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.Pp
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.Fn nvmm_gpa_map
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maps into the guest physical memory beginning on address
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.Fa gpa
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the buffer of size
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.Fa size
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located at address
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.Fa hva
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of the calling process' virtual address space.
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The
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.Fa hva
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parameter must point to a buffer that was previously mapped with
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.Fn nvmm_hva_map .
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.Pp
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.Fn nvmm_gpa_unmap
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removes the guest physical memory area beginning on address
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.Fa gpa
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and of size
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.Fa size
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from the machine
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.Fa mach .
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.Pp
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.Fn nvmm_gva_to_gpa
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translates, on the CPU
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.Fa vcpu
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from the machine
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.Fa mach ,
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the guest virtual address given in
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.Fa gva
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into a guest physical address returned in
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.Fa gpa .
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The associated page premissions are returned in
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.Fa prot .
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.Fa gva
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must be page-aligned.
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.Pp
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.Fn nvmm_gpa_to_hva
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translates, on the machine
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.Fa mach ,
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the guest physical address indicated in
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.Fa gpa
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into a host virtual address returned in
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.Fa hva .
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The associated page premissions are returned in
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.Fa prot .
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.Fa gpa
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must be page-aligned.
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.Pp
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.Fn nvmm_assist_io
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emulates the I/O operation described in
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.Fa vcpu->exit
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on CPU
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.Fa vcpu
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from machine
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.Fa mach .
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See
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.Sx I/O Assist
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below for details.
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.Pp
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.Fn nvmm_assist_mem
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emulates the Mem operation described in
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.Fa vcpu->exit
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on CPU
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.Fa vcpu
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from machine
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.Fa mach .
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See
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.Sx Mem Assist
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below for details.
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.Ss NVMM Initialization
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NVMM initialization is performed by the
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.Fn nvmm_init
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function, which must be invoked by emulator software before any other NVMM
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function.
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.Pp
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.Fn nvmm_init
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opens the NVMM device, and expects to have the proper permissions to do so.
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In a default configuration, this implies being part of the "nvmm" group.
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If using a special configuration, emulator software should arrange to have the
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proper permissions before invoking
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.Fn nvmm_init ,
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and can drop them after the call has completed.
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.Pp
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It is to be noted that
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.Fn nvmm_init
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may perform non-re-entrant operations, and should be called only once.
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.Ss NVMM Capability
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The
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.Cd nvmm_capability
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structure helps emulator software identify the capabilities offered by NVMM on
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the host:
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.Bd -literal
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struct nvmm_capability {
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uint64_t version;
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uint64_t state_size;
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uint64_t max_machines;
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uint64_t max_vcpus;
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uint64_t max_ram;
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struct {
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...
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} arch;
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};
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.Ed
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.Pp
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For example, the
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.Cd max_machines
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field indicates the maximum number of virtual machines supported, while
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.Cd max_vcpus
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indicates the maximum number of VCPUs supported per virtual machine.
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.Ss Machine Ownership
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When a process creates a virtual machine via
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.Fn nvmm_machine_create ,
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it is considered the owner of this machine.
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No other processes than the owner can operate a virtual machine.
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.Pp
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When an owner exits, all the virtual machines associated with it are destroyed,
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if they were not already destroyed by the owner itself via
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.Fn nvmm_machine_destroy .
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.Pp
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Virtual machines are not inherited across
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.Xr fork 2
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operations.
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.Ss Machine Configuration
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Emulator software can configure several parameters of a virtual machine by using
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.Fn nvmm_machine_configure .
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Currently, no parameters are implemented.
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.Ss VCPU Configuration
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Emulator software can configure several parameters of a VCPU by using
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.Fn nvmm_vcpu_configure ,
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which can take the following operations:
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.Bd -literal
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#define NVMM_VCPU_CONF_CALLBACKS 0
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...
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.Ed
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.Pp
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The higher fields depend on the architecture.
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.Ss Guest-Host Mappings
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Each virtual machine has an associated guest physical memory.
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Emulator software is allowed to modify this guest physical memory by mapping
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it into some parts of its virtual address space.
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.Pp
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Emulator software should follow the following steps to achieve that:
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.Pp
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.Bl -bullet -offset indent -compact
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.It
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Call
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.Fn nvmm_hva_map
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to create in the host's virtual address space an area of memory that can
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be shared with a guest.
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Typically, the
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.Fa hva
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parameter will be a pointer to an area that was previously mapped via
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.Fn mmap .
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.Fn nvmm_hva_map
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will replace the content of the area, and will make it read-write (but not
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executable).
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.It
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Make available in the guest an area of guest physical memory, by calling
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.Fn nvmm_gpa_map
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and passing in the
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.Fa hva
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parameter the value that was previously given to
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.Fn nvmm_hva_map .
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.Fn nvmm_gpa_map
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does not replace the content of any memory, it only creates a direct link
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from
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.Fa gpa
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into
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.Fa hva .
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.Fn nvmm_gpa_unmap
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removes this link without modifying
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.Fa hva .
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.El
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.Pp
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The guest will then be able to use the guest physical address passed in the
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.Fa gpa
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parameter of
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.Fn nvmm_gpa_map .
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Each change the guest makes in
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.Fa gpa
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will be reflected in the host's
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.Fa hva ,
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and vice versa.
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.Pp
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It is illegal for emulator software to use
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.Fn munmap
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on an area that was mapped via
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.Fn nvmm_hva_map .
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.Ss VCPU State Area
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A VCPU state area is a structure that entirely defines the content of the
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registers of a VCPU.
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Only one such structure exists, for x86:
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.Bd -literal
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struct nvmm_x64_state {
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struct nvmm_x64_state_seg segs[NVMM_X64_NSEG];
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uint64_t gprs[NVMM_X64_NGPR];
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uint64_t crs[NVMM_X64_NCR];
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uint64_t drs[NVMM_X64_NDR];
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uint64_t msrs[NVMM_X64_NMSR];
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struct nvmm_x64_state_intr intr;
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struct fxsave fpu;
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};
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#define nvmm_vcpu_state nvmm_x64_state
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.Ed
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.Pp
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Refer to functional examples to see precisely how to use this structure.
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.Pp
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A VCPU state area is divided in sub-states.
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A
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.Fa flags
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parameter is used to set and get the VCPU state; it acts as a bitmap which
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indicates which sub-states to set or get.
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.Pp
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During VM exits, a partial VCPU state area is provided in
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.Va exitstate ,
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see
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.Sx Exit Reasons
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below for details.
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.Ss VCPU Programming Model
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A VCPU is described by a public structure,
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.Cd nvmm_vcpu :
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.Bd -literal
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struct nvmm_vcpu {
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nvmm_cpuid_t cpuid;
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struct nvmm_vcpu_state *state;
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struct nvmm_vcpu_event *event;
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struct nvmm_vcpu_exit *exit;
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};
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.Ed
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.Pp
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This structure is used both publicly by emulator software and internally by
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.Nm .
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Emulator software should not modify the pointers of this structure, because
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they are initialized to special values by
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.Nm .
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.Pp
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A call to
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.Fn nvmm_vcpu_getstate
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will fetch the desired parts of the VCPU state and put them in
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.Fa vcpu->state .
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A call to
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.Fn nvmm_vcpu_setstate
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will install in the VCPU the desired parts of
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.Fa vcpu->state .
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A call to
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.Fn nvmm_vcpu_inject
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will inject in the VCPU the event in
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.Fa vcpu->event .
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A call to
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.Fn nvmm_vcpu_run
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will fill
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.Fa vcpu->exit
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with the VCPU exit information.
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.Pp
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If emulator software uses several threads, a VCPU should be associated with
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only one thread, and only this thread should perform VCPU modifications.
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Emulator software should not modify the state of a VCPU with several
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different threads.
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.Ss Exit Reasons
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The
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.Cd nvmm_vcpu_exit
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structure is used to handle VM exits:
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.Bd -literal
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/* Generic. */
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#define NVMM_VCPU_EXIT_NONE 0x0000000000000000ULL
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#define NVMM_VCPU_EXIT_INVALID 0xFFFFFFFFFFFFFFFFULL
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/* x86: operations. */
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#define NVMM_VCPU_EXIT_MEMORY 0x0000000000000001ULL
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#define NVMM_VCPU_EXIT_IO 0x0000000000000002ULL
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/* x86: changes in VCPU state. */
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#define NVMM_VCPU_EXIT_SHUTDOWN 0x0000000000001000ULL
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#define NVMM_VCPU_EXIT_INT_READY 0x0000000000001001ULL
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#define NVMM_VCPU_EXIT_NMI_READY 0x0000000000001002ULL
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#define NVMM_VCPU_EXIT_HALTED 0x0000000000001003ULL
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#define NVMM_VCPU_EXIT_TPR_CHANGED 0x0000000000001004ULL
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/* x86: instructions. */
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#define NVMM_VCPU_EXIT_RDMSR 0x0000000000002000ULL
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#define NVMM_VCPU_EXIT_WRMSR 0x0000000000002001ULL
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#define NVMM_VCPU_EXIT_MONITOR 0x0000000000002002ULL
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#define NVMM_VCPU_EXIT_MWAIT 0x0000000000002003ULL
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#define NVMM_VCPU_EXIT_CPUID 0x0000000000002004ULL
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struct nvmm_vcpu_exit {
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uint64_t reason;
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union {
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...
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} u;
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struct {
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...
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} exitstate;
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};
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.Ed
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.Pp
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The
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.Va reason
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field indicates the reason of the VM exit.
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Additional parameters describing the exit can be present in
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.Va u .
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.Va exitstate
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contains a partial, implementation-specific VCPU state, usable as a fast-path
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to retrieve certain state values.
|
|
.Pp
|
|
It is possible that a VM exit was caused by a reason internal to the host
|
|
kernel, and that emulator software should not be concerned with.
|
|
In this case, the exit reason is set to
|
|
.Cd NVMM_VCPU_EXIT_NONE .
|
|
This gives a chance for emulator software to halt the VM in its tracks.
|
|
.Pp
|
|
Refer to functional examples to see precisely how to handle VM exits.
|
|
.Ss Event Injection
|
|
It is possible to inject an event into a VCPU.
|
|
An event can be a hardware interrupt, a software interrupt, or a software
|
|
exception, defined by:
|
|
.Bd -literal
|
|
#define NVMM_VCPU_EVENT_EXCP 0
|
|
#define NVMM_VCPU_EVENT_INTR 1
|
|
|
|
struct nvmm_vcpu_event {
|
|
u_int type;
|
|
uint8_t vector;
|
|
union {
|
|
struct {
|
|
uint64_t error;
|
|
} excp;
|
|
} u;
|
|
};
|
|
.Ed
|
|
.Pp
|
|
This describes an event of type
|
|
.Va type ,
|
|
to be sent to vector number
|
|
.Va vector ,
|
|
with a possible additional
|
|
.Va error
|
|
code that is implementation-specific.
|
|
.Pp
|
|
It is possible that the VCPU is in a state where it cannot receive this
|
|
event, if:
|
|
.Pp
|
|
.Bl -bullet -offset indent -compact
|
|
.It
|
|
the event is a hardware interrupt, and the VCPU runs with interrupts disabled,
|
|
or
|
|
.It
|
|
the event is a non-maskable interrupt (NMI), and the VCPU is already in an
|
|
in-NMI context.
|
|
.El
|
|
.Pp
|
|
Emulator software can manage interrupt and NMI window-exiting via the
|
|
.Va intr
|
|
component of the VCPU state.
|
|
When such window-exiting is enabled, NVMM will cause a VM exit with reason
|
|
.Cd NVMM_VCPU_EXIT_INT_READY
|
|
or
|
|
.Cd NVMM_VCPU_EXIT_NMI_READY
|
|
to indicate that the guest is now able to handle the corresponding class
|
|
of interrupts.
|
|
.Ss Assist Callbacks
|
|
In order to assist emulation of certain operations,
|
|
.Nm
|
|
requires emulator software to register, via
|
|
.Fn nvmm_vcpu_configure ,
|
|
a set of callbacks described in the following structure:
|
|
.Bd -literal
|
|
struct nvmm_assist_callbacks {
|
|
void (*io)(struct nvmm_io *);
|
|
void (*mem)(struct nvmm_mem *);
|
|
};
|
|
.Ed
|
|
.Pp
|
|
These callbacks are used by
|
|
.Nm
|
|
each time
|
|
.Fn nvmm_assist_io
|
|
or
|
|
.Fn nvmm_assist_mem
|
|
are invoked.
|
|
Emulator software that does not intend to use either of these assists can put
|
|
.Dv NULL
|
|
in the callbacks.
|
|
.Ss I/O Assist
|
|
When a VM exit occurs with reason
|
|
.Cd NVMM_VCPU_EXIT_IO ,
|
|
it is necessary for emulator software to emulate the associated I/O operation.
|
|
.Nm
|
|
provides an easy way for emulator software to perform that.
|
|
.Pp
|
|
.Fn nvmm_assist_io
|
|
will call the registered
|
|
.Fa io
|
|
callback function and give it a
|
|
.Cd nvmm_io
|
|
structure as argument.
|
|
This structure describes an I/O transaction:
|
|
.Bd -literal
|
|
struct nvmm_io {
|
|
struct nvmm_machine *mach;
|
|
struct nvmm_vcpu *vcpu;
|
|
uint16_t port;
|
|
bool in;
|
|
size_t size;
|
|
uint8_t *data;
|
|
};
|
|
.Ed
|
|
.Pp
|
|
The callback can emulate the operation using this descriptor, following two
|
|
unique cases:
|
|
.Pp
|
|
.Bl -bullet -offset indent -compact
|
|
.It
|
|
The operation is an input.
|
|
In this case, the callback should fill
|
|
.Va data
|
|
with the desired value.
|
|
.It
|
|
The operation is an output.
|
|
In this case, the callback should read
|
|
.Va data
|
|
to retrieve the desired value.
|
|
.El
|
|
.Pp
|
|
In either case,
|
|
.Va port
|
|
will indicate the I/O port,
|
|
.Va in
|
|
will indicate if the operation is an input, and
|
|
.Va size
|
|
will indicate the size of the access.
|
|
.Ss Mem Assist
|
|
When a VM exit occurs with reason
|
|
.Cd NVMM_VCPU_EXIT_MEMORY ,
|
|
it is necessary for emulator software to emulate the associated memory
|
|
operation.
|
|
.Nm
|
|
provides an easy way for emulator software to perform that, similar to the I/O
|
|
Assist.
|
|
.Pp
|
|
.Fn nvmm_assist_mem
|
|
will call the registered
|
|
.Fa mem
|
|
callback function and give it a
|
|
.Cd nvmm_mem
|
|
structure as argument.
|
|
This structure describes a Mem transaction:
|
|
.Bd -literal
|
|
struct nvmm_mem {
|
|
struct nvmm_machine *mach;
|
|
struct nvmm_vcpu *vcpu;
|
|
gpaddr_t gpa;
|
|
bool write;
|
|
size_t size;
|
|
uint8_t *data;
|
|
};
|
|
.Ed
|
|
.Pp
|
|
The callback can emulate the operation using this descriptor, following two
|
|
unique cases:
|
|
.Pp
|
|
.Bl -bullet -offset indent -compact
|
|
.It
|
|
The operation is a read.
|
|
In this case, the callback should fill
|
|
.Va data
|
|
with the desired value.
|
|
.It
|
|
The operation is a write.
|
|
In this case, the callback should read
|
|
.Va data
|
|
to retrieve the desired value.
|
|
.El
|
|
.Pp
|
|
In either case,
|
|
.Va gpa
|
|
will indicate the guest physical address,
|
|
.Va write
|
|
will indicate if the access is a write, and
|
|
.Va size
|
|
will indicate the size of the access.
|
|
.Sh RETURN VALUES
|
|
Upon successful completion, each of these functions returns zero.
|
|
Otherwise, a value of \-1 is returned and the global
|
|
variable
|
|
.Va errno
|
|
is set to indicate the error.
|
|
.Sh FILES
|
|
.Bl -tag -width XXXX -compact
|
|
.It Lk https://www.netbsd.org/~maxv/nvmm/nvmm-demo.zip
|
|
Functional example (demonstrator).
|
|
Contains an emulator that uses the
|
|
.Nm
|
|
API, and a small kernel that exercises this emulator.
|
|
.It Pa src/sys/dev/nvmm/
|
|
Source code of the kernel NVMM driver.
|
|
.It Pa src/lib/libnvmm/
|
|
Source code of the
|
|
.Nm
|
|
library.
|
|
.El
|
|
.Sh ERRORS
|
|
These functions will fail if:
|
|
.Bl -tag -width [ENOBUFS]
|
|
.It Bq Er EEXIST
|
|
An attempt was made to create a machine or a VCPU that already exists.
|
|
.It Bq Er EFAULT
|
|
An attempt was made to emulate a memory-based operation in a guest, and the
|
|
guest page tables did not have the permissions necessary for the operation
|
|
to complete successfully.
|
|
.It Bq Er EINVAL
|
|
An inappropriate parameter was used.
|
|
.It Bq Er ENOBUFS
|
|
The maximum number of machines or VCPUs was reached.
|
|
.It Bq Er ENOENT
|
|
A query was made on a machine or a VCPU that does not exist.
|
|
.It Bq Er EPERM
|
|
An attempt was made to access a machine that does not belong to the process.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr nvmm 4 ,
|
|
.Xr nvmmctl 8
|
|
.Sh AUTHORS
|
|
NVMM was designed and implemented by
|
|
.An Maxime Villard .
|