From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756089AbdKQCzH (ORCPT ); Thu, 16 Nov 2017 21:55:07 -0500 Received: from mail-ot0-f193.google.com ([74.125.82.193]:46098 "EHLO mail-ot0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755539AbdKQCzA (ORCPT ); Thu, 16 Nov 2017 21:55:00 -0500 X-Google-Smtp-Source: AGs4zMbqXp0OwhDHhCINzCGUk3V/iKaKO4T0hBfDzf3njvATUCgWoGl94C1honBP9fb39GwmFN0zZQ== Subject: Re: [PATCH 1/2] x86,kvm: move qemu/guest FPU switching out to vcpu_run To: Paolo Bonzini , Rik van Riel , "quan.xu04@gmail.com" Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, david@redhat.com, borntraeger@de.ibm.com, tglx@linutronix.de, rkrcmar@redhat.com References: <20171114215424.32214-1-riel@redhat.com> <20171114215424.32214-2-riel@redhat.com> <2e83dd3f-8f03-03ac-45e0-f2fae1d17013@gmail.com> <1510756981.21121.291.camel@redhat.com> <1510806094.21121.303.camel@redhat.com> <0fc15536-0b34-51b6-cc14-00989825b0bc@gmail.com> <9ba2d4c1-0781-419e-ddeb-77e0494583d2@redhat.com> <00231a24-f1a2-324e-1c32-0a5a7a3995f1@redhat.com> <756023cd-5ba5-bb31-c7cc-7c91b6201632@redhat.com> <8396b51f-674d-74f9-e67f-026504c24631@redhat.com> From: Quan Xu Message-ID: <3da8f4f3-3db1-0c25-9e0e-4d8881145205@gmail.com> Date: Fri, 17 Nov 2017 10:54:50 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <8396b51f-674d-74f9-e67f-026504c24631@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2017-11-17 01:50, Paolo Bonzini wrote: > On 16/11/2017 15:28, Quan Xu wrote: >> vcpu->srcu_idx = srcu_read_lock(&kvm->srcu); >> >> + kvm_load_guest_fpu(vcpu); >> + >> for (;;) { >> if (kvm_vcpu_running(vcpu)) { >> r = vcpu_enter_guest(vcpu); >> >> << >> >> >> >>   as Rik dropped  kvm_load_guest_fpu(vcpu) in  vcpu_enter_guest() .. >>   in case still in kvm mode, how to make sure to pkru is always the >> right one before enter guest mode, not be preempted before >> preempt_disable()  after migration? :( > As you know: > > 1) kvm_load_guest_fpu doesn't load the guest PKRU, it keeps the > userspace PKRU. > > 2) the guest PKRU is only ever set in a preemption-disabled area > > Thus, context switch always sees the userspace PKRU. The guest PKRU is > only set the next time vmx_vcpu_run executes. > > Paolo > Paolo, thanks for your explanation!!:-) Rik, could you cc me in v2? Quan