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

["Chen, Tiejun" <tiejun.chen@intel.com>]

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.
>>>
>
>