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

Wang, Wei W
2014-11-05T08:53:09Z

On 05/11/2014 4:07, 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?

I think both are ok.
If we zero max_irr in vmx_set_rvi(), we still need this check:
if ((is_guest_mode(vcpu) && nested_exit_on_intr(vcpu)) || max_irr == -1)

Let's see if Paolo has any comments, then send out a second version.

Wei
>
> 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.
> >>>
> >
> >