linux-kernel - Re: [PATCH] KVM/X86: Check input sreg values before loading vcpu

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Message-ID: <72e27449-c8fd-c3e3-75c1-07853c49d974@microsoft.com>
Date:   Fri, 9 Mar 2018 07:24:13 +0000
From:   Tianyu Lan <Tianyu.Lan@...rosoft.com>
To:     "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>
CC:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KVM/X86: Check input sreg values before loading vcpu

Hi Radim:
	Thanks for your review.

On 3/9/2018 12:15 AM, rkrcmar@...hat.com wrote:
> 2018-02-27 06:57+0000, Tianyu Lan:
>> From: Lan Tianyu <Tianyu.Lan@...rosoft.com>
>>
>> This patch is to check sreg value first and then load vcpu in order
>> to avoid redundant loading/putting vcpu.
>>
>> Signed-off-by: Lan Tianyu <Tianyu.Lan@...rosoft.com>
>> ---
> 
> Patch "KVM: x86: KVM_CAP_SYNC_REGS" made significant changes to the
> sregs setter, so the patch cannot be applied in current form.
> 
> I think that moving the X86_CR4_OSXSAVE check to guest_cpuid_has still
> makes sense, but avoiding the vcpu_load/put would produce worse code
> elsewhere and avoiding the load/put is not critical as any error is
> probably going to be the end for this VM.
> 

OK. I will update patch.