KVM: Drop interrupt shadow when single stepping should be done only on VMX
The problem exists only on VMX. Also currently we skip this step if
there is pending exception. The patch fixes this too.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index c87c93f..c14bffc 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3453,6 +3453,14 @@
if (test_bit(VCPU_REGS_RIP, (unsigned long *)&vcpu->arch.regs_dirty))
vmcs_writel(GUEST_RIP, vcpu->arch.regs[VCPU_REGS_RIP]);
+ /* When single-stepping over STI and MOV SS, we must clear the
+ * corresponding interruptibility bits in the guest state. Otherwise
+ * vmentry fails as it then expects bit 14 (BS) in pending debug
+ * exceptions being set, but that's not correct for the guest debugging
+ * case. */
+ if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)
+ vmx_set_interrupt_shadow(vcpu, 0);
+
/*
* Loading guest fpu may have cleared host cr0.ts
*/