From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752639AbbASSxD (ORCPT ); Mon, 19 Jan 2015 13:53:03 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38703 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752605AbbASSxB (ORCPT ); Mon, 19 Jan 2015 13:53:01 -0500 Date: Mon, 19 Jan 2015 19:51:51 +0100 From: Oleg Nesterov To: Rik van Riel , 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: [PATCH 2/3] x86, fpu: always allow FPU in interrupt if use_eager_fpu() Message-ID: <20150119185151.GC16427@redhat.com> References: <1421012793-30106-1-git-send-email-riel@redhat.com> <20150115191918.GA27332@redhat.com> <20150119185109.GA16427@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150119185109.GA16427@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- arch/x86/kernel/i387.c | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c index 26f0e80..4734865 100644 --- a/arch/x86/kernel/i387.c +++ b/arch/x86/kernel/i387.c @@ -41,8 +41,8 @@ void kernel_fpu_enable(void) * be set (so that the clts/stts pair does nothing that is * visible in the interrupted kernel thread). * - * Except for the eagerfpu case when we return 1 unless we've already - * been eager and saved the state in kernel_fpu_begin(). + * Except for the eagerfpu case when we return true; in the likely case + * the thread has FPU but we are not going to set/clear TS. */ static inline bool interrupted_kernel_fpu_idle(void) { @@ -50,7 +50,7 @@ static inline bool interrupted_kernel_fpu_idle(void) return false; if (use_eager_fpu()) - return __thread_has_fpu(current); + return true; return !__thread_has_fpu(current) && (read_cr0() & X86_CR0_TS); -- 1.5.5.1