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KVM: Fix unneeded instruction skipping during task switching.

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There is no need to skip instruction if the reason for a task switch
is a task gate in IDT and access to it is caused by an external even.
The problem  is currently solved only for VMX since there is no reliable
way to skip an instruction in SVM. We should emulate it instead.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Gleb Natapov
2009-03-30 16:03:29 +03:00
committed by Avi Kivity
parent b237ac37a1
commit 64a7ec0668
4 changed files with 51 additions and 18 deletions
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25
arch/x86/kvm/svm.c
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@@ -1825,17 +1825,28 @@ static int task_switch_interception(struct vcpu_svm *svm,
struct kvm_run *kvm_run)
{
u16 tss_selector;
int reason;
int int_type = svm->vmcb->control.exit_int_info &
SVM_EXITINTINFO_TYPE_MASK;
tss_selector = (u16)svm->vmcb->control.exit_info_1;
if (svm->vmcb->control.exit_info_2 &
(1ULL << SVM_EXITINFOSHIFT_TS_REASON_IRET))
return kvm_task_switch(&svm->vcpu, tss_selector,
TASK_SWITCH_IRET);
if (svm->vmcb->control.exit_info_2 &
(1ULL << SVM_EXITINFOSHIFT_TS_REASON_JMP))
return kvm_task_switch(&svm->vcpu, tss_selector,
TASK_SWITCH_JMP);
return kvm_task_switch(&svm->vcpu, tss_selector, TASK_SWITCH_CALL);
reason = TASK_SWITCH_IRET;
else if (svm->vmcb->control.exit_info_2 &
(1ULL << SVM_EXITINFOSHIFT_TS_REASON_JMP))
reason = TASK_SWITCH_JMP;
else if (svm->vmcb->control.exit_int_info & SVM_EXITINTINFO_VALID)
reason = TASK_SWITCH_GATE;
else
reason = TASK_SWITCH_CALL;
if (reason != TASK_SWITCH_GATE || int_type == SVM_EXITINTINFO_TYPE_SOFT)
skip_emulated_instruction(&svm->vcpu);
return kvm_task_switch(&svm->vcpu, tss_selector, reason);
}
static int cpuid_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)