From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 276ADC433E0 for ; Tue, 19 Jan 2021 18:56:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D9C5D20776 for ; Tue, 19 Jan 2021 18:55:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730575AbhASSzt (ORCPT ); Tue, 19 Jan 2021 13:55:49 -0500 Received: from mail.kernel.org ([198.145.29.99]:48614 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389648AbhASS1e (ORCPT ); Tue, 19 Jan 2021 13:27:34 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 181D3236FB; Tue, 19 Jan 2021 17:39:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1611077956; bh=B0nbVoxGa+C36Jr6OtipmAgpoS6EnZrHQCygC20qrDA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MsJg6AXHEtuAuqFIh5+SYsRWNP8NhdiGwyA9ltZA6EBRCg0yIAiFsLWNbu6tCUnVg 9+Fzbu3l+VLV5eT0fbKciA1BAbypqP8YJTFkbPFDjsKpI1zsGHIdmfbhFanuudyZur /HoieVnZIFS06hDPDFTJSirgmjPosvu1lHJ25wYQjERmgII6rR64K8nJrOXndh9OmV pqPY8o6L3k7uL4mb5FA8G1CeLPnYdHdYoXGkJvOrkwUjFtbuN7+t2TCcVMlZrrZY/E dM8YhDPUW9EzPaLewj53NdieI6D92/2tpiEdTgLRJR8qyb51W8MxIdOYNQvoTXqflM 4t7t9uLR5FZ/w== From: Andy Lutomirski To: x86@kernel.org Cc: LKML , Krzysztof Mazur , =?UTF-8?q?Krzysztof=20Ol=C4=99dzki?= , Arnd Bergmann , Andy Lutomirski Subject: [PATCH v2 2/4] x86/mmx: Use KFPU_387 for MMX string operations Date: Tue, 19 Jan 2021 09:39:00 -0800 Message-Id: X-Mailer: git-send-email 2.29.2 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The default kernel_fpu_begin() doesn't work on systems that support XMM but haven't yet enabled CR4.OSFXSR. This causes crashes when _mmx_memcpy() is called too early because LDMXCSR generates #UD when the aforementioned bit is clear. Fix it by using kernel_fpu_begin_mask(KFPU_387) explicitly. Fixes: 7ad816762f9b ("x86/fpu: Reset MXCSR to default in kernel_fpu_begin()") Reported-by: Krzysztof Mazur Signed-off-by: Andy Lutomirski --- arch/x86/lib/mmx_32.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) diff --git a/arch/x86/lib/mmx_32.c b/arch/x86/lib/mmx_32.c index 4321fa02e18d..2a6ad7aa148a 100644 --- a/arch/x86/lib/mmx_32.c +++ b/arch/x86/lib/mmx_32.c @@ -26,6 +26,16 @@ #include #include +/* + * For MMX, we use KFPU_387. MMX instructions are not affected by MXCSR, + * but both AMD and Intel documentation states that even integer MMX + * operations will result in #MF if an exception is pending in FCW. + * + * We don't need EMMS afterwards because, after we call kernel_fpu_end(), + * any subsequent user of the 387 stack will reinitialize it using + * KFPU_387. + */ + void *_mmx_memcpy(void *to, const void *from, size_t len) { void *p; @@ -37,7 +47,7 @@ void *_mmx_memcpy(void *to, const void *from, size_t len) p = to; i = len >> 6; /* len/64 */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(KFPU_387); __asm__ __volatile__ ( "1: prefetch (%0)\n" /* This set is 28 bytes */ @@ -127,7 +137,7 @@ static void fast_clear_page(void *page) { int i; - kernel_fpu_begin(); + kernel_fpu_begin_mask(KFPU_387); __asm__ __volatile__ ( " pxor %%mm0, %%mm0\n" : : @@ -160,7 +170,7 @@ static void fast_copy_page(void *to, void *from) { int i; - kernel_fpu_begin(); + kernel_fpu_begin_mask(KFPU_387); /* * maybe the prefetch stuff can go before the expensive fnsave... @@ -247,7 +257,7 @@ static void fast_clear_page(void *page) { int i; - kernel_fpu_begin(); + kernel_fpu_begin_mask(KFPU_387); __asm__ __volatile__ ( " pxor %%mm0, %%mm0\n" : : @@ -282,7 +292,7 @@ static void fast_copy_page(void *to, void *from) { int i; - kernel_fpu_begin(); + kernel_fpu_begin_mask(KFPU_387); __asm__ __volatile__ ( "1: prefetch (%0)\n" -- 2.29.2