Previous to this change, a vCPU exposed with VMX running on a kernel
without KVM_CAP_NESTED_STATE or KVM_CAP_EXCEPTION_PAYLOAD resulted in
adding a migration blocker. This was because when the code was written
it was thought there is no way to reliably know if a vCPU is utilising
VMX or not at runtime. However, it turns out that this can be known to
some extent:
In order for a vCPU to enter VMX operation it must have CR4.VMXE set.
Since it was set, CR4.VMXE must remain set as long as the vCPU is in
VMX operation. This is because CR4.VMXE is one of the bits set
in MSR_IA32_VMX_CR4_FIXED1.
There is one exception to the above statement when vCPU enters SMM mode.
When a vCPU enters SMM mode, it temporarily exits VMX operation and
may also reset CR4.VMXE during execution in SMM mode.
When the vCPU exits SMM mode, vCPU state is restored to be in VMX operation
and CR4.VMXE is restored to its original state of being set.
Therefore, when the vCPU is not in SMM mode, we can infer whether
VMX is being used by examining CR4.VMXE. Otherwise, we cannot
know for certain but assume the worse that vCPU may utilise VMX.
Summaring all the above, a vCPU may have enabled VMX in case
CR4.VMXE is set or vCPU is in SMM mode.
Therefore, remove migration blocker and check before migration
(cpu_pre_save()) if the vCPU may have enabled VMX. If true, only then
require relevant kernel capabilities.
While at it, demand KVM_CAP_EXCEPTION_PAYLOAD only when the vCPU is in
guest-mode and there is a pending/injected exception. Otherwise, this
kernel capability is not required for proper migration.
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Liran Alon <liran.alon@oracle.com>
Reviewed-by: Maran Wilson <maran.wilson@oracle.com>
Tested-by: Maran Wilson <maran.wilson@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Hyper-V identifies vCPUs by Virtual Processor (VP) index which can be
queried by the guest via HV_X64_MSR_VP_INDEX msr. It is defined by the
spec as a sequential number which can't exceed the maximum number of
vCPUs per VM.
It has to be owned by QEMU in order to preserve it across migration.
However, the initial implementation in KVM didn't allow to set this
msr, and KVM used its own notion of VP index. Fortunately, the way
vCPUs are created in QEMU/KVM makes it likely that the KVM value is
equal to QEMU cpu_index.
So choose cpu_index as the value for vp_index, and push that to KVM on
kernels that support setting the msr. On older ones that don't, query
the kernel value and assert that it's in sync with QEMU.
Besides, since handling errors from vCPU init at hotplug time is
impossible, disable vCPU hotplug.
This patch also introduces accessor functions to encapsulate the mapping
between a vCPU and its vp_index.
Signed-off-by: Roman Kagan <rkagan@virtuozzo.com>
Message-Id: <20180702134156.13404-3-rkagan@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Switch to the header we imported from Linux,
this allows us to drop a hack in kvm_i386.h.
More code will be dropped in the next patch.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
pc.h and sysemu/kvm.h are also included from common code (where
CONFIG_KVM is not available), so the #defines that depend on CONFIG_KVM
should not be declared here to avoid that anybody is using them in a
wrong way. Since we're also going to poison CONFIG_KVM for common code,
let's move them to kvm_i386.h instead. Most of the dummy definitions
from sysemu/kvm.h are also unused since the code that uses them is
only compiled for CONFIG_KVM (e.g. target/i386/kvm.c), so the unused
defines are also simply dropped here instead of being moved.
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <1498454578-18709-3-git-send-email-thuth@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Check for KVM_CAP_ADJUST_CLOCK capability KVM_CLOCK_TSC_STABLE, which
indicates that KVM_GET_CLOCK returns a value as seen by the guest at
that moment.
For new machine types, use this value rather than reading
from guest memory.
This reduces kvmclock difference on migration from 5s to 0.1s
(when max_downtime == 5s).
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Message-Id: <20161121105052.598267440@redhat.com>
[Add comment explaining what is going on. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
We've currently got 18 architectures in QEMU, and thus 18 target-xxx
folders in the root folder of the QEMU source tree. More architectures
(e.g. RISC-V, AVR) are likely to be included soon, too, so the main
folder of the QEMU sources slowly gets quite overcrowded with the
target-xxx folders.
To disburden the main folder a little bit, let's move the target-xxx
folders into a dedicated target/ folder, so that target-xxx/ simply
becomes target/xxx/ instead.
Acked-by: Laurent Vivier <laurent@vivier.eu> [m68k part]
Acked-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de> [tricore part]
Acked-by: Michael Walle <michael@walle.cc> [lm32 part]
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com> [s390x part]
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com> [s390x part]
Acked-by: Eduardo Habkost <ehabkost@redhat.com> [i386 part]
Acked-by: Artyom Tarasenko <atar4qemu@gmail.com> [sparc part]
Acked-by: Richard Henderson <rth@twiddle.net> [alpha part]
Acked-by: Max Filippov <jcmvbkbc@gmail.com> [xtensa part]
Reviewed-by: David Gibson <david@gibson.dropbear.id.au> [ppc part]
Acked-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com> [crisµblaze part]
Acked-by: Guan Xuetao <gxt@mprc.pku.edu.cn> [unicore32 part]
Signed-off-by: Thomas Huth <thuth@redhat.com>
