From patchwork Wed Feb 3 18:35:11 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Kani, Toshi" X-Patchwork-Id: 8206851 Return-Path: X-Original-To: patchwork-linux-nvdimm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 4B5569F4DD for ; Wed, 3 Feb 2016 18:36:28 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 3CB8A20266 for ; Wed, 3 Feb 2016 18:36:27 +0000 (UTC) Received: from ml01.01.org (ml01.01.org [198.145.21.10]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 346A6202C8 for ; Wed, 3 Feb 2016 18:36:26 +0000 (UTC) Received: from ml01.vlan14.01.org (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id ED97B1A1E1C; Wed, 3 Feb 2016 10:36:25 -0800 (PST) X-Original-To: linux-nvdimm@lists.01.org Delivered-To: linux-nvdimm@lists.01.org Received: from g4t3425.houston.hp.com (g4t3425.houston.hp.com [15.201.208.53]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 756AB1A1E1B for ; Wed, 3 Feb 2016 10:36:24 -0800 (PST) Received: from g4t3433.houston.hp.com (g4t3433.houston.hp.com [16.210.25.219]) by g4t3425.houston.hp.com (Postfix) with ESMTP id 0A07D32; Wed, 3 Feb 2016 18:36:23 +0000 (UTC) Received: from misato.fc.hp.com (misato.fc.hp.com [16.78.168.61]) by g4t3433.houston.hp.com (Postfix) with ESMTP id 566A45B; Wed, 3 Feb 2016 18:36:21 +0000 (UTC) From: Toshi Kani To: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, bp@suse.de, dan.j.williams@intel.com Subject: [PATCH v2] x86/lib/copy_user_64.S: Handle 4-byte nocache copy Date: Wed, 3 Feb 2016 11:35:11 -0700 Message-Id: <1454524511-29416-1-git-send-email-toshi.kani@hpe.com> X-Mailer: git-send-email 2.4.3 Cc: linux-nvdimm@lists.01.org, x86@kernel.org, linux-kernel@vger.kernel.org, micah.parrish@hpe.com, brian.boylston@hpe.com X-BeenThere: linux-nvdimm@lists.01.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: "Linux-nvdimm developer list." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" X-Spam-Status: No, score=-2.3 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_NONE, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Data corruption issues were observed in tests which initiated a system crash/reset while accessing BTT devices. This problem is reproducible. The BTT driver calls pmem_rw_bytes() to update data in pmem devices. This interface calls __copy_user_nocache(), which uses non-temporal stores so that the stores to pmem are persistent. __copy_user_nocache() uses non-temporal stores when a request size is 8 bytes or larger (and is aligned by 8 bytes). The BTT driver updates the BTT map table, which entry size is 4 bytes. Therefore, updates to the map table entries remain cached, and are not written to pmem after a crash. Change __copy_user_nocache() to use non-temporal store when a request size is 4 bytes. The change extends the current byte-copy path for a less-than-8-bytes request, and does not add any overhead to the regular path. Also add comments to the code, and clarify the cases that lead cache copy. Reported-and-tested-by: Micah Parrish Reported-and-tested-by: Brian Boylston Signed-off-by: Toshi Kani Cc: Thomas Gleixner Cc: Ingo Molnar Cc: H. Peter Anvin Cc: Borislav Petkov Cc: Dan Williams Cc: Ross Zwisler Cc: Vishal Verma --- v2: - Add comments (Ingo Molnar). - Make this patch as an individual patch since v2 debug changes will not depend on this patch. --- arch/x86/lib/copy_user_64.S | 74 +++++++++++++++++++++++++++++++++++-------- 1 file changed, 61 insertions(+), 13 deletions(-) diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S index 982ce34..1641327 100644 --- a/arch/x86/lib/copy_user_64.S +++ b/arch/x86/lib/copy_user_64.S @@ -232,17 +232,30 @@ ENDPROC(copy_user_enhanced_fast_string) /* * copy_user_nocache - Uncached memory copy with exception handling - * This will force destination/source out of cache for more performance. + * This will force destination out of cache for more performance. + * + * Note: Cached memory copy is used when destination or size is not + * naturally aligned. That is: + * - Require 8-byte alignment when size is 8 bytes or larger. + * - Require 4-byte alignment when size is 4 bytes. */ ENTRY(__copy_user_nocache) ASM_STAC + + /* If size is less than 8 bytes, goto 4-byte copy */ cmpl $8,%edx - jb 20f /* less then 8 bytes, go to byte copy loop */ + jb 20f + + /* If destination is not 8-byte aligned, "cache" copy to align it */ ALIGN_DESTINATION + + /* Set 4x8-byte copy count and remainder */ movl %edx,%ecx andl $63,%edx shrl $6,%ecx - jz 17f + jz 17f /* If count is 0, goto 8-byte copy */ + + /* Perform 4x8-byte nocache loop-copy */ 1: movq (%rsi),%r8 2: movq 1*8(%rsi),%r9 3: movq 2*8(%rsi),%r10 @@ -263,26 +276,57 @@ ENTRY(__copy_user_nocache) leaq 64(%rdi),%rdi decl %ecx jnz 1b + + /* Set 8-byte copy count and remainder */ 17: movl %edx,%ecx andl $7,%edx shrl $3,%ecx - jz 20f + jz 20f /* If count is 0, goto 4-byte copy */ + + /* Perform 8-byte nocache loop-copy */ 18: movq (%rsi),%r8 19: movnti %r8,(%rdi) leaq 8(%rsi),%rsi leaq 8(%rdi),%rdi decl %ecx jnz 18b + + /* If no byte left, we're done */ 20: andl %edx,%edx - jz 23f + jz 26f + + /* If destination is not 4-byte aligned, goto byte copy */ + movl %edi,%ecx + andl $3,%ecx + jnz 23f + + /* Set 4-byte copy count (1 or 0) and remainder */ movl %edx,%ecx -21: movb (%rsi),%al -22: movb %al,(%rdi) + andl $3,%edx + shrl $2,%ecx + jz 23f /* If count is 0, goto byte copy */ + + /* Perform 4-byte nocache copy */ +21: movl (%rsi),%r8d +22: movnti %r8d,(%rdi) + leaq 4(%rsi),%rsi + leaq 4(%rdi),%rdi + + /* If no byte left, we're done */ + andl %edx,%edx + jz 26f + + /* Perform byte "cache" loop-copy for the remainder */ +23: movl %edx,%ecx +24: movb (%rsi),%al +25: movb %al,(%rdi) incq %rsi incq %rdi decl %ecx - jnz 21b -23: xorl %eax,%eax + jnz 24b + + /* Finished copying; fence the prior stores */ +26: xorl %eax,%eax ASM_CLAC sfence ret @@ -290,11 +334,13 @@ ENTRY(__copy_user_nocache) .section .fixup,"ax" 30: shll $6,%ecx addl %ecx,%edx - jmp 60f + jmp 70f 40: lea (%rdx,%rcx,8),%rdx - jmp 60f -50: movl %ecx,%edx -60: sfence + jmp 70f +50: lea (%rdx,%rcx,4),%rdx + jmp 70f +60: movl %ecx,%edx +70: sfence jmp copy_user_handle_tail .previous @@ -318,4 +364,6 @@ ENTRY(__copy_user_nocache) _ASM_EXTABLE(19b,40b) _ASM_EXTABLE(21b,50b) _ASM_EXTABLE(22b,50b) + _ASM_EXTABLE(24b,60b) + _ASM_EXTABLE(25b,60b) ENDPROC(__copy_user_nocache)