Re: [PATCH] KVM: x86: reset RVI upon system reset

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On 2014/11/5 15:39, Wang, Wei W wrote:
On 05/11/2014 2:14, Tiejun Chen wrote:
A bug was reported as follows: when running Windows 7 32-bit guests on
qemu-kvm, sometimes the guests run into blue screen during reboot. The
problem was that a guest's RVI was not cleared when it rebooted. This
patch has fixed the problem.

Signed-off-by: Wei Wang <wei.w.wang@xxxxxxxxx>
Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
Tested-by: Rongrong Liu <rongrongx.liu@xxxxxxxxx>, Da Chun
<ngugc@xxxxxx>
---
   arch/x86/kvm/lapic.c |    3 +++
   arch/x86/kvm/vmx.c   |   12 ++++++------
   2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index
66dd173..6942742 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1712,6 +1712,9 @@ void kvm_apic_post_state_restore(struct
kvm_vcpu *vcpu,
   	apic->isr_count = kvm_apic_vid_enabled(vcpu->kvm) ?
   				1 : count_vectors(apic->regs + APIC_ISR);
   	apic->highest_isr_cache = -1;
+	if (kvm_x86_ops->hwapic_irr_update)
+		kvm_x86_ops->hwapic_irr_update(vcpu,
+				apic_find_highest_irr(apic));

Could we pass 0 directly? Because looks we just need to clear RVI.

kvm_x86_ops->hwapic_irr_update(vcpu, 0);

I think this already makes sense based on your description.

Thanks
Tiejun

No. This is a restore function, and we cannot assume that the callers always need to reset to the initial state.

Okay. Maybe I'm confused by the following change.


Wei

   	kvm_x86_ops->hwapic_isr_update(vcpu->kvm,
apic_find_highest_isr(apic));
   	kvm_make_request(KVM_REQ_EVENT, vcpu);
   	kvm_rtc_eoi_tracking_restore_one(vcpu);
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index
fe4d2f4..d632548 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -7292,19 +7292,19 @@ static void vmx_set_rvi(int vector)
   static void vmx_hwapic_irr_update(struct kvm_vcpu *vcpu, int max_irr)
   {
   	if (max_irr == -1)
+		max_irr = 0;
+
+	if (!is_guest_mode(vcpu)) {
+		vmx_set_rvi(max_irr);
   		return;
+	}

   	/*
   	 * If a vmexit is needed, vmx_check_nested_events handles it.
   	 */
-	if (is_guest_mode(vcpu) && nested_exit_on_intr(vcpu))
+	if ((is_guest_mode(vcpu) && nested_exit_on_intr(vcpu)) || max_irr
==
+0)

Its really not readable to modify max_irr as 0 and check that here, and especially when you read the original comment.

So what about this?

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 0cd99d8..bc4558b 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -7280,6 +7280,9 @@ static void vmx_set_rvi(int vector)
        u16 status;
        u8 old;

+       if (vector == -1)
+               vector = 0;
+
        status = vmcs_read16(GUEST_INTR_STATUS);
        old = (u8)status & 0xff;
        if ((u8)vector != old) {
@@ -7291,9 +7294,6 @@ static void vmx_set_rvi(int vector)

 static void vmx_hwapic_irr_update(struct kvm_vcpu *vcpu, int max_irr)
 {
-       if (max_irr == -1)
-               return;
-
        /*
         * If a vmexit is needed, vmx_check_nested_events handles it.
         */
@@ -7305,6 +7305,9 @@ static void vmx_hwapic_irr_update(struct kvm_vcpu *vcpu, int max_irr)
                return;
        }

+       if (max_irr == -1)
+               return;
+
        /*
         * Fall back to pre-APICv interrupt injection since L2
         * is run without virtual interrupt delivery.


Thanks
Tiejun

   		return;

-	if (!is_guest_mode(vcpu)) {
-		vmx_set_rvi(max_irr);
-		return;
-	}
-
   	/*
   	 * Fall back to pre-APICv interrupt injection since L2
   	 * is run without virtual interrupt delivery.



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