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From:   Thomas Gleixner <tglx@linutronix.de>
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To:     "Liu, Jing2" <jing2.liu@linux.intel.com>,
        LKML <linux-kernel@vger.kernel.org>
Cc:     Yang Zhong <yang.zhong@intel.com>,
        Paolo Bonzini <pbonzini@redhat.com>, x86@kernel.org,
        kvm@vger.kernel.org, Sean Christoperson <seanjc@google.com>,
        Jin Nakajima <jun.nakajima@intel.com>,
        Kevin Tian <kevin.tian@intel.com>
Subject: Re: [patch 6/6] x86/fpu: Provide kvm_sync_guest_vmexit_xfd_state()
In-Reply-To: <62cc7ba5-8a46-2396-e728-cf5902c22306@linux.intel.com>
References: <20211214022825.563892248@linutronix.de>
 <20211214024948.108057289@linutronix.de>
 <62cc7ba5-8a46-2396-e728-cf5902c22306@linux.intel.com>
Date:   Wed, 15 Dec 2021 10:49:18 +0100
Message-ID: <87ee6erye9.ffs@tglx>
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Jing,

On Wed, Dec 15 2021 at 14:35, Jing2 Liu wrote:
> On 12/14/2021 10:50 AM, Thomas Gleixner wrote:
>> KVM can disable the write emulation for the XFD MSR when the vCPU's fpstate
>> is already correctly sized to reduce the overhead.
>>
>> When write emulation is disabled the XFD MSR state after a VMEXIT is
>> unknown and therefore not in sync with the software states in fpstate and
>> the per CPU XFD cache.
>>
>> Provide kvm_sync_guest_vmexit_xfd_state() which has to be invoked after a
>> VMEXIT before enabling interrupts when write emulation is disabled for the
>> XFD MSR.
> Thanks for this function.
>
> s/kvm_sync_guest_vmexit_xfd_state/fpu_sync_guest_vmexit_xfd_state
> in subject and changelog.

I clearly need more sleep.