[tip: x86/fred] x86/cpufeatures,opcode,msr: Add the WRMSRNS instruction support

From: tip-bot2 for Xin Li
Date: Thu Jan 25 2024 - 13:29:43 EST

The following commit has been merged into the x86/fred branch of tip:

Commit-ID: a4cb5ece145828cae35503857debf3d49c9d1c5f
Gitweb: https://git.kernel.org/tip/a4cb5ece145828cae35503857debf3d49c9d1c5f
Author: Xin Li <xin3.li@xxxxxxxxx>
AuthorDate: Tue, 05 Dec 2023 02:49:50 -08:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Thu, 25 Jan 2024 19:10:29 +01:00

x86/cpufeatures,opcode,msr: Add the WRMSRNS instruction support

WRMSRNS is an instruction that behaves exactly like WRMSR, with
the only difference being that it is not a serializing instruction
by default. Under certain conditions, WRMSRNS may replace WRMSR to
improve performance.

Add its CPU feature bit, opcode to the x86 opcode map, and an
always inline API __wrmsrns() to embed WRMSRNS into the code.

Signed-off-by: Xin Li <xin3.li@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Shan Kang <shan.kang@xxxxxxxxx>
Acked-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Acked-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Link: https://lore.kernel.org/r/20231205105030.8698-2-xin3.li@xxxxxxxxx

---
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/include/asm/msr.h | 18 ++++++++++++++++++
arch/x86/lib/x86-opcode-map.txt | 2 +-
tools/arch/x86/include/asm/cpufeatures.h | 1 +
tools/arch/x86/lib/x86-opcode-map.txt | 2 +-
5 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 29cb275..bd05c75 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -327,6 +327,7 @@
#define X86_FEATURE_FSRS (12*32+11) /* "" Fast short REP STOSB */
#define X86_FEATURE_FSRC (12*32+12) /* "" Fast short REP {CMPSB,SCASB} */
#define X86_FEATURE_LKGS (12*32+18) /* "" Load "kernel" (userspace) GS */
+#define X86_FEATURE_WRMSRNS (12*32+19) /* "" Non-serializing WRMSR */
#define X86_FEATURE_AMX_FP16 (12*32+21) /* "" AMX fp16 Support */
#define X86_FEATURE_AVX_IFMA (12*32+23) /* "" Support for VPMADD52[H,L]UQ */
#define X86_FEATURE_LAM (12*32+26) /* Linear Address Masking */
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 65ec196..c284ff9 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -97,6 +97,19 @@ static __always_inline void __wrmsr(unsigned int msr, u32 low, u32 high)
: : "c" (msr), "a"(low), "d" (high) : "memory");
}

+/*
+ * WRMSRNS behaves exactly like WRMSR with the only difference being
+ * that it is not a serializing instruction by default.
+ */
+static __always_inline void __wrmsrns(u32 msr, u32 low, u32 high)
+{
+ /* Instruction opcode for WRMSRNS; supported in binutils >= 2.40. */
+ asm volatile("1: .byte 0x0f,0x01,0xc6\n"
+ "2:\n"
+ _ASM_EXTABLE_TYPE(1b, 2b, EX_TYPE_WRMSR)
+ : : "c" (msr), "a"(low), "d" (high));
+}
+
#define native_rdmsr(msr, val1, val2) \
do { \
u64 __val = __rdmsr((msr)); \
@@ -297,6 +310,11 @@ do { \

#endif /* !CONFIG_PARAVIRT_XXL */

+static __always_inline void wrmsrns(u32 msr, u64 val)
+{
+ __wrmsrns(msr, val, val >> 32);
+}
+
/*
* 64-bit version of wrmsr_safe():
*/
diff --git a/arch/x86/lib/x86-opcode-map.txt b/arch/x86/lib/x86-opcode-map.txt
index 5168ee0..1efe1d9 100644
--- a/arch/x86/lib/x86-opcode-map.txt
+++ b/arch/x86/lib/x86-opcode-map.txt
@@ -1051,7 +1051,7 @@ GrpTable: Grp6
EndTable

GrpTable: Grp7
-0: SGDT Ms | VMCALL (001),(11B) | VMLAUNCH (010),(11B) | VMRESUME (011),(11B) | VMXOFF (100),(11B) | PCONFIG (101),(11B) | ENCLV (000),(11B)
+0: SGDT Ms | VMCALL (001),(11B) | VMLAUNCH (010),(11B) | VMRESUME (011),(11B) | VMXOFF (100),(11B) | PCONFIG (101),(11B) | ENCLV (000),(11B) | WRMSRNS (110),(11B)
1: SIDT Ms | MONITOR (000),(11B) | MWAIT (001),(11B) | CLAC (010),(11B) | STAC (011),(11B) | ENCLS (111),(11B)
2: LGDT Ms | XGETBV (000),(11B) | XSETBV (001),(11B) | VMFUNC (100),(11B) | XEND (101)(11B) | XTEST (110)(11B) | ENCLU (111),(11B)
3: LIDT Ms
diff --git a/tools/arch/x86/include/asm/cpufeatures.h b/tools/arch/x86/include/asm/cpufeatures.h
index f4542d2..8792841 100644
--- a/tools/arch/x86/include/asm/cpufeatures.h
+++ b/tools/arch/x86/include/asm/cpufeatures.h
@@ -322,6 +322,7 @@
#define X86_FEATURE_FSRS (12*32+11) /* "" Fast short REP STOSB */
#define X86_FEATURE_FSRC (12*32+12) /* "" Fast short REP {CMPSB,SCASB} */
#define X86_FEATURE_LKGS (12*32+18) /* "" Load "kernel" (userspace) GS */
+#define X86_FEATURE_WRMSRNS (12*32+19) /* "" Non-serializing WRMSR */
#define X86_FEATURE_AMX_FP16 (12*32+21) /* "" AMX fp16 Support */
#define X86_FEATURE_AVX_IFMA (12*32+23) /* "" Support for VPMADD52[H,L]UQ */
#define X86_FEATURE_LAM (12*32+26) /* Linear Address Masking */
diff --git a/tools/arch/x86/lib/x86-opcode-map.txt b/tools/arch/x86/lib/x86-opcode-map.txt
index 5168ee0..1efe1d9 100644
--- a/tools/arch/x86/lib/x86-opcode-map.txt
+++ b/tools/arch/x86/lib/x86-opcode-map.txt
@@ -1051,7 +1051,7 @@ GrpTable: Grp6
EndTable

GrpTable: Grp7
-0: SGDT Ms | VMCALL (001),(11B) | VMLAUNCH (010),(11B) | VMRESUME (011),(11B) | VMXOFF (100),(11B) | PCONFIG (101),(11B) | ENCLV (000),(11B)
+0: SGDT Ms | VMCALL (001),(11B) | VMLAUNCH (010),(11B) | VMRESUME (011),(11B) | VMXOFF (100),(11B) | PCONFIG (101),(11B) | ENCLV (000),(11B) | WRMSRNS (110),(11B)
1: SIDT Ms | MONITOR (000),(11B) | MWAIT (001),(11B) | CLAC (010),(11B) | STAC (011),(11B) | ENCLS (111),(11B)
2: LGDT Ms | XGETBV (000),(11B) | XSETBV (001),(11B) | VMFUNC (100),(11B) | XEND (101)(11B) | XTEST (110)(11B) | ENCLU (111),(11B)
3: LIDT Ms