[PATCH 1/4] x86/cpufeatures: Add enumeration for SERIALIZE instruction

From: Ricardo Neri
Date: Mon Jul 27 2020 - 00:32:36 EST

The Intel architecture defines a set of Serializing Instructions (a
detailed definition can be found in Vol.3 Section 8.3 of the Intel "main"
manual, SDM). However, these instructions do more than what is required,
have side effects and/or may be rather invasive. Furthermore, some of
these instructions are only available in kernel mode or may cause VMExits.
Thus, software using these instructions only to serialize execution (as
defined in the manual) must handle the undesired side effects.

As indicated in the name, SERIALIZE is a new Intel architecture
Serializing Instruction. Crucially, it does not have any of the mentioned
side effects. Also, it does not cause VMExit and can be used in user mode.

This new instruction is currently documented in the latest "extensions"
manual (ISE). It will appear in the "main" manual in the future.

Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Cathy Zhang <cathy.zhang@xxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Kyung Min Park <kyung.min.park@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: "Ravi V. Shankar" <ravi.v.shankar@xxxxxxxxx>
Cc: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: linux-edac@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Acked-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>
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 03390a1ef8e7..2901d5df4366 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -367,6 +367,7 @@
#define X86_FEATURE_SRBDS_CTRL (18*32+ 9) /* "" SRBDS mitigation MSR available */
#define X86_FEATURE_MD_CLEAR (18*32+10) /* VERW clears CPU buffers */
#define X86_FEATURE_TSX_FORCE_ABORT (18*32+13) /* "" TSX_FORCE_ABORT */
+#define X86_FEATURE_SERIALIZE (18*32+14) /* SERIALIZE instruction */
#define X86_FEATURE_PCONFIG (18*32+18) /* Intel PCONFIG */
#define X86_FEATURE_ARCH_LBR (18*32+19) /* Intel ARCH LBR */
#define X86_FEATURE_SPEC_CTRL (18*32+26) /* "" Speculation Control (IBRS + IBPB) */