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/x86.c b/arch/x86/kvm/x86.c
index adcf738..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 */