[tip: x86/mm] x86/idle: Remove CONFIG_AS_TPAUSE

[tip-bot2 for Uros Bizjak]

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

Commit-ID:     cdc018e6b1c403b6a94416acea4649f9778c68c0
Gitweb:        https://git.kernel.org/tip/cdc018e6b1c403b6a94416acea4649f9778c68c0
Author:        Uros Bizjak <ubizjak@xxxxxxxxx>
AuthorDate:    Wed, 02 Apr 2025 20:08:08 +02:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Wed, 02 Apr 2025 22:37:09 +02:00

x86/idle: Remove CONFIG_AS_TPAUSE

There is not much point in CONFIG_AS_TPAUSE at all when the emittedu
assembly is always the same - it only obfuscates the __tpause() code
in essence.

Remove the TPAUSE insn mnemonic from __tpause() and leave only
the equivalent byte-wise definition. This can then be changed
back to insn mnemonic once binutils 2.31.1 is the minimum version
to build the kernel. (Right now it's 2.25.)

Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20250402180827.3762-4-ubizjak@xxxxxxxxx
---
 arch/x86/Kconfig.assembler   |  4 ----
 arch/x86/include/asm/mwait.h | 11 ++---------
 2 files changed, 2 insertions(+), 13 deletions(-)

diff --git a/arch/x86/Kconfig.assembler b/arch/x86/Kconfig.assembler
index 6d20a6c..fa88585 100644
--- a/arch/x86/Kconfig.assembler
+++ b/arch/x86/Kconfig.assembler
@@ -15,10 +15,6 @@ config AS_SHA256_NI
 	def_bool $(as-instr,sha256msg1 %xmm0$(comma)%xmm1)
 	help
 	  Supported by binutils >= 2.24 and LLVM integrated assembler
-config AS_TPAUSE
-	def_bool $(as-instr,tpause %ecx)
-	help
-	  Supported by binutils >= 2.31.1 and LLVM integrated assembler >= V7
 
 config AS_GFNI
 	def_bool $(as-instr,vgf2p8mulb %xmm0$(comma)%xmm1$(comma)%xmm2)
diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h
index 6522886..5141d2a 100644
--- a/arch/x86/include/asm/mwait.h
+++ b/arch/x86/include/asm/mwait.h
@@ -133,16 +133,9 @@ static __always_inline void mwait_idle_with_hints(unsigned long eax, unsigned lo
  */
 static inline void __tpause(u32 ecx, u32 edx, u32 eax)
 {
-	/* "tpause %ecx, %edx, %eax" */
-	#ifdef CONFIG_AS_TPAUSE
-	asm volatile("tpause %%ecx"
-		     :
-		     : "c"(ecx), "d"(edx), "a"(eax));
-	#else
+	/* "tpause %ecx" */
 	asm volatile(".byte 0x66, 0x0f, 0xae, 0xf1"
-		     :
-		     : "c"(ecx), "d"(edx), "a"(eax));
-	#endif
+		     :: "c" (ecx), "d" (edx), "a" (eax));
 }
 
 #endif /* _ASM_X86_MWAIT_H */