linux-kernel - Re: [PATCH v2 2/2] KVM: LAPIC: Guarantee the timer is in tsc-deadline mode when setting

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Message-ID: <20200813145830.GF29439@linux.intel.com>
Date:   Thu, 13 Aug 2020 07:58:30 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Wanpeng Li <kernellwp@...il.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH v2 2/2] KVM: LAPIC: Guarantee the timer is in
 tsc-deadline mode when setting

On Wed, Aug 12, 2020 at 02:30:38PM +0800, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@...cent.com>
> 
> Check apic_lvtt_tscdeadline() mode directly instead of apic_lvtt_oneshot()
> and apic_lvtt_period() to guarantee the timer is in tsc-deadline mode when
> wrmsr MSR_IA32_TSCDEADLINE.
> 
> Signed-off-by: Wanpeng Li <wanpengli@...cent.com>

Gah, I take back my comment about squashing these, I assumed this was the
same fix but just in the write path.

Reviewed-by: Sean Christopherson <sean.j.christopherson@...el.com>

> ---
> v1 -> v2:
>  * fix indentation
> 
>  arch/x86/kvm/lapic.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 79599af..abaf48e 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -2193,8 +2193,7 @@ void kvm_set_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu, u64 data)
>  {
>  	struct kvm_lapic *apic = vcpu->arch.apic;
>  
> -	if (!kvm_apic_present(vcpu) || apic_lvtt_oneshot(apic) ||
> -			apic_lvtt_period(apic))
> +	if (!kvm_apic_present(vcpu) || !apic_lvtt_tscdeadline(apic))
>  		return;
>  
>  	hrtimer_cancel(&apic->lapic_timer.timer);
> -- 
> 2.7.4
>