Commit-ID: ca7d9b795e6bc78c80a1771ada867994fabcfc01 Gitweb: http://git.kernel.org/tip/ca7d9b795e6bc78c80a1771ada867994fabcfc01 Author: Ross Zwisler <ross.zwis...@linux.intel.com> AuthorDate: Mon, 11 May 2015 10:15:51 +0200 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Mon, 11 May 2015 10:38:44 +0200
x86/mm: Add kerneldoc comments for pcommit_sfence() 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 <ross.zwis...@linux.intel.com> Signed-off-by: Borislav Petkov <b...@suse.de> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Andy Lutomirski <l...@amacapital.net> Cc: Borislav Petkov <b...@alien8.de> Cc: Brian Gerst <brge...@gmail.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: H Peter Anvin <h.peter.an...@intel.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Luis R. Rodriguez <mcg...@suse.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Toshi Kani <toshi.k...@hp.com> Link: http://lkml.kernel.org/r/1430261196-2401-1-git-send-email-ross.zwis...@linux.intel.com Link: http://lkml.kernel.org/r/1431332153-18566-7-git-send-email...@alien8.de Signed-off-by: Ingo Molnar <mi...@kernel.org> --- 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 aeb4666e..2270e41 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, -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
