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([2001:b07:6468:f312:9def:34a0:b68d:9993]) by smtp.gmail.com with ESMTPSA id c8sm11521398wrt.19.2020.03.03.23.58.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Mar 2020 23:58:56 -0800 (PST) Subject: Re: [PATCH 3/4] KVM: x86: Revert "KVM: X86: Fix fpu state crash in kvm guest" To: "Liu, Jing2" , Sean Christopherson Cc: Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Derek Yerger , kernel@najdan.com, Thomas Lambertz , Rik van Riel , Sebastian Andrzej Siewior , Borislav Petkov , Dave Hansen , Thomas Gleixner References: <20200117062628.6233-1-sean.j.christopherson@intel.com> <20200117062628.6233-4-sean.j.christopherson@intel.com> From: Paolo Bonzini Message-ID: <3c467967-a499-af4e-29df-ddfeb196714f@redhat.com> Date: Wed, 4 Mar 2020 08:58:55 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/03/20 08:41, Liu, Jing2 wrote: >>       trace_kvm_entry(vcpu->vcpu_id); >>       guest_enter_irqoff(); >>   -    /* The preempt notifier should have taken care of the FPU >> already.  */ >> -    WARN_ON_ONCE(test_thread_flag(TIF_NEED_FPU_LOAD)); >> +    fpregs_assert_state_consistent(); >> +    if (test_thread_flag(TIF_NEED_FPU_LOAD)) >> +        switch_fpu_return(); >>         if (unlikely(vcpu->arch.switch_db_regs)) { >>           set_debugreg(0, 7); > > Can kvm be preempt out again after this (before really enter to guest)? No, irqs are disabled here. Paolo