linux-kernel - Re: [PATCH 15/19] kvm: x86: Save and restore guest XFD

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Message-ID: <fbfb1377-a6e7-a0c0-2001-606c6529ce0f@redhat.com>
Date:   Fri, 10 Dec 2021 17:23:22 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Yang Zhong <yang.zhong@...el.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com
Cc:     seanjc@...gle.com, jun.nakajima@...el.com, kevin.tian@...el.com,
        jing2.liu@...ux.intel.com, jing2.liu@...el.com
Subject: Re: [PATCH 15/19] kvm: x86: Save and restore guest XFD_ERR properly

On 12/8/21 01:03, Yang Zhong wrote:
>   		kvm_steal_time_set_preempted(vcpu);
>   	srcu_read_unlock(&vcpu->kvm->srcu, idx);
>   
> +	if (vcpu->preempted)
> +		fpu_save_guest_xfd_err(&vcpu->arch.guest_fpu);
> +

Instead of checking vcpu->preempted, can you instead check if the active 
FPU is the guest FPU?  That is, save if 
current->thread.fpu->fpstate->is_guest?

Paolo