From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752382AbbATOqk (ORCPT ); Tue, 20 Jan 2015 09:46:40 -0500 Received: from mx1.redhat.com ([209.132.183.28]:53955 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751396AbbATOqj (ORCPT ); Tue, 20 Jan 2015 09:46:39 -0500 Message-ID: <54BE6A41.5030004@redhat.com> Date: Tue, 20 Jan 2015 09:46:25 -0500 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Oleg Nesterov , Linus Torvalds , Suresh Siddha CC: linux-kernel@vger.kernel.org, mingo@redhat.com, hpa@zytor.com, matt.fleming@intel.com, bp@suse.de, pbonzini@redhat.com, tglx@linutronix.de, luto@amacapital.net Subject: Re: [PATCH 2/3] x86, fpu: always allow FPU in interrupt if use_eager_fpu() References: <1421012793-30106-1-git-send-email-riel@redhat.com> <20150115191918.GA27332@redhat.com> <20150119185109.GA16427@redhat.com> <20150119185151.GC16427@redhat.com> In-Reply-To: <20150119185151.GC16427@redhat.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/19/2015 01:51 PM, Oleg Nesterov wrote: > The __thread_has_fpu() check in interrupted_kernel_fpu_idle() was needed > to prevent the nested kernel_fpu_begin(). Now that we have in_kernel_fpu > and !__thread_has_fpu() case in __kernel_fpu_begin() does not depend on > use_eager_fpu() (except clts) we can remove it. > > __thread_has_fpu() can be false even if use_eager_fpu(), but this case > does not differ from !use_eager_fpu() case except we should not worry > about X86_CR0_TS, __kernel_fpu_begin/end will not touch this bit. > > Note: I think we can kill all irq_fpu_usable() checks except in_kernel_fpu, > just we need to record the state of X86_CR0_TS in __kernel_fpu_begin() and > conditionalize stts() in __kernel_fpu_end(), but this needs another patch. > > Signed-off-by: Oleg Nesterov Reviewed-by: Rik van Riel