ddf0fd9ae1
The GSI callback (and later PCI_INTX) is a level triggered interrupt. It is asserted when an event channel is delivered to vCPU0, and is supposed to be cleared when the vcpu_info->evtchn_upcall_pending field for vCPU0 is cleared again. Thankfully, Xen does *not* assert the GSI if the guest sets its own evtchn_upcall_pending field; we only need to assert the GSI when we have delivered an event for ourselves. So that's the easy part, kind of. There's a slight complexity in that we need to hold the BQL before we can call qemu_set_irq(), and we definitely can't do that while holding our own port_lock (because we'll need to take that from the qemu-side functions that the PV backend drivers will call). So if we end up wanting to set the IRQ in a context where we *don't* already hold the BQL, defer to a BH. However, we *do* need to poll for the evtchn_upcall_pending flag being cleared. In an ideal world we would poll that when the EOI happens on the PIC/IOAPIC. That's how it works in the kernel with the VFIO eventfd pairs — one is used to trigger the interrupt, and the other works in the other direction to 'resample' on EOI, and trigger the first eventfd again if the line is still active. However, QEMU doesn't seem to do that. Even VFIO level interrupts seem to be supported by temporarily unmapping the device's BARs from the guest when an interrupt happens, then trapping *all* MMIO to the device and sending the 'resample' event on *every* MMIO access until the IRQ is cleared! Maybe in future we'll plumb the 'resample' concept through QEMU's irq framework but for now we'll do what Xen itself does: just check the flag on every vmexit if the upcall GSI is known to be asserted. Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Reviewed-by: Paul Durrant <paul@xen.org>
34 lines
1.0 KiB
C
34 lines
1.0 KiB
C
/*
|
|
* Xen HVM emulation support in KVM
|
|
*
|
|
* Copyright © 2019 Oracle and/or its affiliates. All rights reserved.
|
|
* Copyright © 2022 Amazon.com, Inc. or its affiliates. All Rights Reserved.
|
|
*
|
|
* This work is licensed under the terms of the GNU GPL, version 2 or later.
|
|
* See the COPYING file in the top-level directory.
|
|
*
|
|
*/
|
|
|
|
#ifndef QEMU_I386_KVM_XEN_EMU_H
|
|
#define QEMU_I386_KVM_XEN_EMU_H
|
|
|
|
#define XEN_HYPERCALL_MSR 0x40000000
|
|
#define XEN_HYPERCALL_MSR_HYPERV 0x40000200
|
|
|
|
#define XEN_CPUID_SIGNATURE 0
|
|
#define XEN_CPUID_VENDOR 1
|
|
#define XEN_CPUID_HVM_MSR 2
|
|
#define XEN_CPUID_TIME 3
|
|
#define XEN_CPUID_HVM 4
|
|
|
|
#define XEN_VERSION(maj, min) ((maj) << 16 | (min))
|
|
|
|
int kvm_xen_init(KVMState *s, uint32_t hypercall_msr);
|
|
int kvm_xen_init_vcpu(CPUState *cs);
|
|
int kvm_xen_handle_exit(X86CPU *cpu, struct kvm_xen_exit *exit);
|
|
int kvm_put_xen_state(CPUState *cs);
|
|
int kvm_get_xen_state(CPUState *cs);
|
|
void kvm_xen_maybe_deassert_callback(CPUState *cs);
|
|
|
|
#endif /* QEMU_I386_KVM_XEN_EMU_H */
|