linux-kernel - Re: [patch 4/6] x86/fpu: Add guest support to xfd_enable

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Message-ID: <f49f9358-a903-3ee1-46f8-1662911390ef@redhat.com>
Date:   Tue, 14 Dec 2021 11:21:51 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Jing Liu <jing2.liu@...ux.intel.com>,
        "Zhong, Yang" <yang.zhong@...el.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "Nakajima, Jun" <jun.nakajima@...el.com>
Subject: Re: [patch 4/6] x86/fpu: Add guest support to xfd_enable_feature()

On 12/14/21 07:05, Tian, Kevin wrote:
>> +	if (guest_fpu) {
>> +		newfps->is_guest = true;
>> +		newfps->is_confidential = curfps->is_confidential;
>> +		newfps->in_use = curfps->in_use;
>> +		guest_fpu->xfeatures |= xfeatures;
>> +	}
>> +
> As you explained guest fpstate is not current active in the restoring
> path, thus it's not correct to always inherit attributes from the
> active one.

Indeed, guest_fpu->fpstate should be used instead of curfps.

Paolo