From 33823f4d63f7a010653d219800539409a78ef4be Mon Sep 17 00:00:00 2001 From: Fenghua Yu Date: Wed, 24 Oct 2018 14:57:16 -0700 Subject: [PATCH] x86/cpufeatures: Enumerate MOVDIRI instruction MOVDIRI moves doubleword or quadword from register to memory through direct store which is implemented by using write combining (WC) for writing data directly into memory without caching the data. Programmable agents can handle streaming offload (e.g. high speed packet processing in network). Hardware implements a doorbell (tail pointer) register that is updated by software when adding new work-elements to the streaming offload work-queue. MOVDIRI can be used as the doorbell write which is a 4-byte or 8-byte uncachable write to MMIO. MOVDIRI has lower overhead than other ways to write the doorbell. Availability of the MOVDIRI instruction is indicated by the presence of the CPUID feature flag MOVDIRI(CPUID.0x07.0x0:ECX[bit 27]). Please check the latest Intel Architecture Instruction Set Extensions and Future Features Programming Reference for more details on the CPUID feature MOVDIRI flag. Signed-off-by: Fenghua Yu Cc: Andy Lutomirski Cc: Ashok Raj Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Ravi V Shankar Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1540418237-125817-2-git-send-email-fenghua.yu@intel.com Signed-off-by: Ingo Molnar --- arch/x86/include/asm/cpufeatures.h | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index 89a048c..90934ee 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -331,6 +331,7 @@ #define X86_FEATURE_LA57 (16*32+16) /* 5-level page tables */ #define X86_FEATURE_RDPID (16*32+22) /* RDPID instruction */ #define X86_FEATURE_CLDEMOTE (16*32+25) /* CLDEMOTE instruction */ +#define X86_FEATURE_MOVDIRI (16*32+27) /* MOVDIRI instruction */ /* AMD-defined CPU features, CPUID level 0x80000007 (EBX), word 17 */ #define X86_FEATURE_OVERFLOW_RECOV (17*32+ 0) /* MCA overflow recovery support */ -- 2.7.4