KVM: Fix unneeded instruction skipping during task switching.
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>
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index de74104..bba67b7 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1825,17 +1825,28 @@
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)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index e4ad9d3..c6997c0 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3038,22 +3038,40 @@
struct vcpu_vmx *vmx = to_vmx(vcpu);
unsigned long exit_qualification;
u16 tss_selector;
- int reason;
+ int reason, type, idt_v;
+
+ idt_v = (vmx->idt_vectoring_info & VECTORING_INFO_VALID_MASK);
+ type = (vmx->idt_vectoring_info & VECTORING_INFO_TYPE_MASK);
exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
reason = (u32)exit_qualification >> 30;
- if (reason == TASK_SWITCH_GATE && vmx->vcpu.arch.nmi_injected &&
- (vmx->idt_vectoring_info & VECTORING_INFO_VALID_MASK) &&
- (vmx->idt_vectoring_info & VECTORING_INFO_TYPE_MASK)
- == INTR_TYPE_NMI_INTR) {
- vcpu->arch.nmi_injected = false;
- if (cpu_has_virtual_nmis())
- vmcs_set_bits(GUEST_INTERRUPTIBILITY_INFO,
- GUEST_INTR_STATE_NMI);
+ if (reason == TASK_SWITCH_GATE && idt_v) {
+ switch (type) {
+ case INTR_TYPE_NMI_INTR:
+ vcpu->arch.nmi_injected = false;
+ if (cpu_has_virtual_nmis())
+ vmcs_set_bits(GUEST_INTERRUPTIBILITY_INFO,
+ GUEST_INTR_STATE_NMI);
+ break;
+ case INTR_TYPE_EXT_INTR:
+ kvm_clear_interrupt_queue(vcpu);
+ break;
+ case INTR_TYPE_HARD_EXCEPTION:
+ case INTR_TYPE_SOFT_EXCEPTION:
+ kvm_clear_exception_queue(vcpu);
+ break;
+ default:
+ break;
+ }
}
tss_selector = exit_qualification;
+ if (!idt_v || (type != INTR_TYPE_HARD_EXCEPTION &&
+ type != INTR_TYPE_EXT_INTR &&
+ type != INTR_TYPE_NMI_INTR))
+ skip_emulated_instruction(vcpu);
+
if (!kvm_task_switch(vcpu, tss_selector, reason))
return 0;
@@ -3306,7 +3324,7 @@
vector = idt_vectoring_info & VECTORING_INFO_VECTOR_MASK;
type = idt_vectoring_info & VECTORING_INFO_TYPE_MASK;
- switch(type) {
+ switch (type) {
case INTR_TYPE_NMI_INTR:
vmx->vcpu.arch.nmi_injected = true;
/*
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index adcf7387..bb04f11 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3935,7 +3935,10 @@
kvm_x86_ops->set_rflags(vcpu, eflags & ~X86_EFLAGS_NT);
}
- kvm_x86_ops->skip_emulated_instruction(vcpu);
+ /* set back link to prev task only if NT bit is set in eflags
+ note that old_tss_sel is not used afetr this point */
+ if (reason != TASK_SWITCH_CALL && reason != TASK_SWITCH_GATE)
+ old_tss_sel = 0xffff;
/* set back link to prev task only if NT bit is set in eflags
note that old_tss_sel is not used afetr this point */
