Since Paolo has removed irq-enable-operation in vmx_handle_external_intr
(KVM: x86: use guest_exit_irqoff), the original comment about the IF bit
in rflags is incorrect now.
Signed-off-by: Longpeng(Mike) <longpeng2@xxxxxxxxxx>
---
arch/x86/kvm/vmx.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index cf1b16d..9fa3c76 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8647,9 +8647,12 @@ static void vmx_handle_external_intr(struct kvm_vcpu *vcpu)
register void *__sp asm(_ASM_SP);
/*
- * If external interrupt exists, IF bit is set in rflags/eflags on the
- * interrupt stack frame, and interrupt will be enabled on a return
- * from interrupt handler.
+ * If external interrupt exists, fakes an interrupt stack and jump to
+ * idt table to let real handler to handle it. Because most of bits in
+ * rflags are cleared when VM exit(Intel SDM volum 3, chapter 27.5.3),
+ * the IF bit is 0 in rflags on the interrupt stack frame, so interrupt
+ * is still disabled when return from the irq handler, but it will be
+ * enabled later by the caller.
*/
if ((exit_intr_info & (INTR_INFO_VALID_MASK | INTR_INFO_INTR_TYPE_MASK))
== (INTR_INFO_VALID_MASK | INTR_TYPE_EXT_INTR)) {
--
2.7.4
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