diff options
| author | Oliver Upton <oupton@google.com> | 2020-02-07 02:36:06 -0800 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2020-02-12 12:34:10 +0100 |
| commit | a06230b62b898e51cfb1de256b2042a09a691f58 (patch) | |
| tree | 0e93155a12a1ab62d71ec6a3dad55576bc621ddb /arch/x86 | |
| parent | 684c0422da71da0cd81319c90b8099b563b13da4 (diff) | |
| download | linux-a06230b62b898e51cfb1de256b2042a09a691f58.tar.bz2 | |
KVM: x86: Deliver exception payload on KVM_GET_VCPU_EVENTS
KVM allows the deferral of exception payloads when a vCPU is in guest
mode to allow the L1 hypervisor to intercept certain events (#PF, #DB)
before register state has been modified. However, this behavior is
incompatible with the KVM_{GET,SET}_VCPU_EVENTS ABI, as userspace
expects register state to have been immediately modified. Userspace may
opt-in for the payload deferral behavior with the
KVM_CAP_EXCEPTION_PAYLOAD per-VM capability. As such,
kvm_multiple_exception() will immediately manipulate guest registers if
the capability hasn't been requested.
Since the deferral is only necessary if a userspace ioctl were to be
serviced at the same as a payload bearing exception is recognized, this
behavior can be relaxed. Instead, opportunistically defer the payload
from kvm_multiple_exception() and deliver the payload before completing
a KVM_GET_VCPU_EVENTS ioctl.
Signed-off-by: Oliver Upton <oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kvm/x86.c | 29 |
1 files changed, 16 insertions, 13 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 95b753dab207..4d3310df1758 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -498,19 +498,7 @@ static void kvm_multiple_exception(struct kvm_vcpu *vcpu, vcpu->arch.exception.error_code = error_code; vcpu->arch.exception.has_payload = has_payload; vcpu->arch.exception.payload = payload; - /* - * In guest mode, payload delivery should be deferred, - * so that the L1 hypervisor can intercept #PF before - * CR2 is modified (or intercept #DB before DR6 is - * modified under nVMX). However, for ABI - * compatibility with KVM_GET_VCPU_EVENTS and - * KVM_SET_VCPU_EVENTS, we can't delay payload - * delivery unless userspace has enabled this - * functionality via the per-VM capability, - * KVM_CAP_EXCEPTION_PAYLOAD. - */ - if (!vcpu->kvm->arch.exception_payload_enabled || - !is_guest_mode(vcpu)) + if (!is_guest_mode(vcpu)) kvm_deliver_exception_payload(vcpu); return; } @@ -3804,6 +3792,21 @@ static void kvm_vcpu_ioctl_x86_get_vcpu_events(struct kvm_vcpu *vcpu, process_nmi(vcpu); /* + * In guest mode, payload delivery should be deferred, + * so that the L1 hypervisor can intercept #PF before + * CR2 is modified (or intercept #DB before DR6 is + * modified under nVMX). Unless the per-VM capability, + * KVM_CAP_EXCEPTION_PAYLOAD, is set, we may not defer the delivery of + * an exception payload and handle after a KVM_GET_VCPU_EVENTS. Since we + * opportunistically defer the exception payload, deliver it if the + * capability hasn't been requested before processing a + * KVM_GET_VCPU_EVENTS. + */ + if (!vcpu->kvm->arch.exception_payload_enabled && + vcpu->arch.exception.pending && vcpu->arch.exception.has_payload) + kvm_deliver_exception_payload(vcpu); + + /* * The API doesn't provide the instruction length for software * exceptions, so don't report them. As long as the guest RIP * isn't advanced, we should expect to encounter the exception |