From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753137AbbEKIRJ (ORCPT ); Mon, 11 May 2015 04:17:09 -0400 Received: from mail.skyhub.de ([78.46.96.112]:55973 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752403AbbEKIQB (ORCPT ); Mon, 11 May 2015 04:16:01 -0400 From: Borislav Petkov To: Ingo Molnar Cc: LKML Subject: [PATCH 2/5] x86/mm: Add kerneldoc comments for pcommit_sfence() Date: Mon, 11 May 2015 10:15:51 +0200 Message-Id: <1431332153-18566-7-git-send-email-bp@alien8.de> X-Mailer: git-send-email 2.3.5 In-Reply-To: <1431332153-18566-1-git-send-email-bp@alien8.de> References: <1431332153-18566-1-git-send-email-bp@alien8.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ross Zwisler Add kerneldoc comments for pcommit_sfence() describing the purpose of the PCOMMIT instruction and demonstrating its usage with an example. Signed-off-by: Ross Zwisler Cc: H Peter Anvin Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Borislav Petkov Link: http://lkml.kernel.org/r/1430261196-2401-1-git-send-email-ross.zwisler@linux.intel.com Signed-off-by: Borislav Petkov --- arch/x86/include/asm/special_insns.h | 38 ++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h index aeb4666e0c0a..2270e41b32fd 100644 --- a/arch/x86/include/asm/special_insns.h +++ b/arch/x86/include/asm/special_insns.h @@ -215,6 +215,44 @@ static inline void clwb(volatile void *__p) : [pax] "a" (p)); } +/** + * pcommit_sfence() - persistent commit and fence + * + * The PCOMMIT instruction ensures that data that has been flushed from the + * processor's cache hierarchy with CLWB, CLFLUSHOPT or CLFLUSH is accepted to + * memory and is durable on the DIMM. The primary use case for this is + * persistent memory. + * + * This function shows how to properly use CLWB/CLFLUSHOPT/CLFLUSH and PCOMMIT + * with appropriate fencing. + * + * Example: + * void flush_and_commit_buffer(void *vaddr, unsigned int size) + * { + * unsigned long clflush_mask = boot_cpu_data.x86_clflush_size - 1; + * void *vend = vaddr + size; + * void *p; + * + * for (p = (void *)((unsigned long)vaddr & ~clflush_mask); + * p < vend; p += boot_cpu_data.x86_clflush_size) + * clwb(p); + * + * // SFENCE to order CLWB/CLFLUSHOPT/CLFLUSH cache flushes + * // MFENCE via mb() also works + * wmb(); + * + * // PCOMMIT and the required SFENCE for ordering + * pcommit_sfence(); + * } + * + * After this function completes the data pointed to by 'vaddr' has been + * accepted to memory and will be durable if the 'vaddr' points to persistent + * memory. + * + * PCOMMIT must always be ordered by an MFENCE or SFENCE, so to help simplify + * things we include both the PCOMMIT and the required SFENCE in the + * alternatives generated by pcommit_sfence(). + */ static inline void pcommit_sfence(void) { alternative(ASM_NOP7, -- 2.3.5