From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757195AbdKOJXw (ORCPT ); Wed, 15 Nov 2017 04:23:52 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38794 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751189AbdKOJXs (ORCPT ); Wed, 15 Nov 2017 04:23:48 -0500 Subject: Re: [PATCH] x86,kvm: move qemu/guest FPU switching out to vcpu_run To: Paolo Bonzini , Rik van Riel Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, rkrcmar@redhat.com, borntraeger@de.ibm.com References: <20171114001223.441ea2ca@annuminas.surriel.com> <1510682877.30057.1.camel@redhat.com> <6f73cff1-eddf-7dc6-a93c-31c20e8520d7@redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <980be73e-828d-d844-d2ab-ea91ec2844e6@redhat.com> Date: Wed, 15 Nov 2017 10:23:46 +0100 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: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Wed, 15 Nov 2017 09:23:48 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15.11.2017 09:34, Paolo Bonzini wrote: > On 14/11/2017 20:40, David Hildenbrand wrote: >> I think we should check all get/put_fpu callers if they need >> preempt_disable(). >> >> E.g. em_fxrstor() needs disabled preemption as we temporarily >> save + restore some host register (via fxsave + fxrstor) under some >> circumstances that are not saved/restored when switching to/back from >> another process. We should double check. > > Rik may correct me, but I believe that you don't need > preempt_disable/enable because preempt notifiers do this for you. > Seems to boil down to what Wanpeng Li asked about preempt notifiers in response to v2. -- Thanks, David / dhildenb