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/include/asm/svm.h b/arch/x86/include/asm/svm.h
index 82ada75f3ebf142678325968ea6fa0952308e9a0..85574b7c1bc13c371c4c5bdc8d17146897f95645 100644 (file)
--- a/arch/x86/include/asm/svm.h
+++ b/arch/x86/include/asm/svm.h
@@ -225,6 +225,7 @@ struct __attribute__ ((__packed__)) vmcb {
 #define SVM_EVTINJ_VALID_ERR (1 << 11)
 
 #define SVM_EXITINTINFO_VEC_MASK SVM_EVTINJ_VEC_MASK
+#define SVM_EXITINTINFO_TYPE_MASK SVM_EVTINJ_TYPE_MASK
 
 #define        SVM_EXITINTINFO_TYPE_INTR SVM_EVTINJ_TYPE_INTR
 #define        SVM_EXITINTINFO_TYPE_NMI SVM_EVTINJ_TYPE_NMI

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index de741043c5b1540bb628217cc6760d531af7cfb6..bba67b70c4b01212513a85640865f8035a03b047 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -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)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index e4ad9d3c0636e447f42269368ed269708dc3a409..c6997c0e8ca643f8b67be4c0e2c5e970be58076f 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3038,22 +3038,40 @@ static int handle_task_switch(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
        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 @@ static void vmx_complete_interrupts(struct vcpu_vmx *vmx)
        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 adcf73871a9dd7015833eb584fbbad07ff1027f3..bb04f11bf70f588c7a605100207c8be487be9403 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3935,7 +3935,10 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int reason)
                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 */