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

Chen, Tiejun
2014-11-05T08:06:48Z

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@intel.com>
>>> Signed-off-by: Yang Zhang <yang.z.zhang@intel.com>
>>> Tested-by: Rongrong Liu <rongrongx.liu@intel.com>, Da Chun
>>> <ngugc@qq.com>
>>> ---
>>> 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.
>>>
>
>