linux-kernel - Re: [PATCH] KVM: x86: Add a WARN on TIF_NEED_FPU_LOAD in kvm_load_guest

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Date:   Tue, 10 Dec 2019 11:29:00 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: Add a WARN on TIF_NEED_FPU_LOAD in
 kvm_load_guest_fpu()

On 09/12/19 21:05, Sean Christopherson wrote:
> +	/*
> +	 * Reloading userspace's FPU is handled by kvm_arch_vcpu_load(), both
> +	 * for direct calls from userspace (via vcpu_load()) and if this task
> +	 * is preempted (via kvm_arch_sched_in()) between vcpu_load() and now.

via kvm_sched_in (not the arch_ function).  Applied with that change.

Paolo

> +	 */
> +	WARN_ON_ONCE(test_thread_flag(TIF_NEED_FPU_LOAD));
> +