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: <4EF1C9E9.50805@siemens.com>
Date:	Wed, 21 Dec 2011 12:58:33 +0100
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Avi Kivity <avi@...hat.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 2011-12-21 12:45, Avi Kivity wrote:
> 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.

I'm not on facebook. Does anyone sell shirts with that?

> 
>> 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

Ah, the adult crowd that trusts the other side.

OK, will see that I can cook up a proper patch later.

Jan

-- 
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
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