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Subject: Re: [PATCH 3/4] KVM: x86: Revert "KVM: X86: Fix fpu state crash in
 kvm guest"
To:     "Liu, Jing2" <jing2.liu@linux.intel.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>
Cc:     Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, Derek Yerger <derek@djy.llc>,
        kernel@najdan.com, Thomas Lambertz <mail@thomaslambertz.de>,
        Rik van Riel <riel@surriel.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Borislav Petkov <bp@suse.de>,
        Dave Hansen <dave.hansen@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>
References: <20200117062628.6233-1-sean.j.christopherson@intel.com>
 <20200117062628.6233-4-sean.j.christopherson@intel.com>
 <ca47fce8-a042-f967-513c-93cabac2122d@linux.intel.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <3c467967-a499-af4e-29df-ddfeb196714f@redhat.com>
Date:   Wed, 4 Mar 2020 08:58:55 +0100
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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