This patch fix a external interrupt injecting bug in linux 3.19-rc4.
GuestOS is running and handling some interrupt with RFLAGS.IF = 0 while a
external interrupt coming,
then can lead to a vm exit,in this case,we must avoid inject this external
interrupt or it will generate
a processor hardware exception causing virtual machine crash.
Now, I show more details about this problem:
A general external interrupt processing for a running virtual machine is shown
in the following:
Step 1:
a ext intr gen a vm_exit --> vmx_complete_interrupts -->
__vmx_complete_interrupts --> case INTR_TYPE_EXT_INR: kvm_queue_interrupt(vcpu,
vector, type == INTR_TYPE_SOFT_INTR);
Step 2:
kvm_x86_ops->handle_external_intr(vcpu);
Step 3:
get back to vcpu_enter_guest after a while cycle,then run
inject_pending_event
Step 4:
if (vcpu->arch.interrupt.pending) {
kvm_x86_ops->set_irq(vcpu);
return 0;
}
Step 5:
kvm_x86_ops->run(vcpu) --> vm_entry inject vector to guestos IDT
for the above steps, step 4 and 5 will be a processor hardware exception if
step1 happen while guestos RFLAGS.IF = 0, that is to say, guestos interrupt is
disabled.
So we should add a logic to judge in step 1 whether a external interrupt need
to be pended then inject directly, in the process, we don't need to worry about
this external interrupt lost because the next Step 2 will handle and choose a
best chance to inject it by virtual interrupt controller.
Signed-off-by: Li kaihang <li.kaih...@zte.com.cn>
---
arch/x86/kvm/vmx.c | 20 ++++++++++++++++++--
1 files changed, 18 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index d4c58d8..e8311ee 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -7711,10 +7711,26 @@ static void __vmx_complete_interrupts(struct kvm_vcpu
*vcpu,
break;
case INTR_TYPE_SOFT_INTR:
vcpu->arch.event_exit_inst_len = vmcs_read32(instr_len_field);
- /* fall through */
- case INTR_TYPE_EXT_INTR:
+ /*
+ * As software and external interrupts may all get here,
+ * we should separate soft intr from ext intr code,and this
+ * will ensure that software interrupts handling process is not
+ * affected by solving external interrupt invalid injecting.
+ */
kvm_queue_interrupt(vcpu, vector, type == INTR_TYPE_SOFT_INTR);
break;
+ case INTR_TYPE_EXT_INTR:
+ /*
+ * GuestOS is running and handling some interrupt with
+ * RFLAGS.IF = 0 while a external interrupt coming,
+ * then can lead a vm exit getting here,in this case,
+ * we must avoid inject this external interrupt or it will
+ * generate a processor hardware exception causing vm crash.
+ */
+ if (kvm_x86_ops->interrupt_allowed(vcpu))
+ kvm_queue_interrupt(vcpu, vector,
+ type == INTR_TYPE_SOFT_INTR);
+ break;
default:
break;
}
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