linux-kernel - Re: [PATCH v2] KVM: x86: Prevent exposing TSC deadline timer feature in the absence of in-kernel APIC

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Message-ID: <4EF1C6C5.6080300@redhat.com>
Date:	Wed, 21 Dec 2011 13:45:09 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Jan Kiszka <jan.kiszka@...mens.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alexey Zaytsev <alexey.zaytsev@...il.com>,
	"Liu, Jinsong" <jinsong.liu@...el.com>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	"Garrett D'Amore" <garrett@...enta.com>, kvm <kvm@...r.kernel.org>
Subject: Re: [PATCH v2] KVM: x86: Prevent exposing TSC deadline timer feature
 in the absence of in-kernel APIC

On 12/21/2011 01:28 PM, Jan Kiszka wrote:
> > 
> > timer_mode_mask can just be slaved to the bit (as received by
> > KVM_SET_CPUID); that's exactly kvm_update_cpuid()'s role.
>
> Like

Ugh, the facebook generation invades lkml.

> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 230f713..89b02bf 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -27,7 +27,6 @@ void kvm_update_cpuid(struct kvm_vcpu *vcpu)
>  {
>  	struct kvm_cpuid_entry2 *best;
>  	struct kvm_lapic *apic = vcpu->arch.apic;
> -	u32 timer_mode_mask;
>
>  	best = kvm_find_cpuid_entry(vcpu, 1, 0);
>  	if (!best)
> @@ -40,15 +39,12 @@ void kvm_update_cpuid(struct kvm_vcpu *vcpu)
>  			best->ecx |= bit(X86_FEATURE_OSXSAVE);
>  	}
>
> -	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
> -		best->function == 0x1) {
> -		best->ecx |= bit(X86_FEATURE_TSC_DEADLINE_TIMER);
> -		timer_mode_mask = 3 << 17;
> -	} else
> -		timer_mode_mask = 1 << 17;
> -
> -	if (apic)
> -		apic->lapic_timer.timer_mode_mask = timer_mode_mask;
> +	if (apic) {
> +		if (best->ecx & bit(X86_FEATURE_TSC_DEADLINE_TIMER))
> +			apic->lapic_timer.timer_mode_mask = 3 << 17;
> +		else
> +			apic->lapic_timer.timer_mode_mask = 1 << 17;
> +	}
>
>  	kvm_pmu_cpuid_update(vcpu);
>  }
>
>
> + the KVM_CAP thing?
>

+1

-- 
error compiling committee.c: too many arguments to function

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