[PATCH -tip] x86/idle: Work around LLVM assembler bug with MONITOR and MWAIT insn

[Uros Bizjak]

LLVM assembler is not able to assemble correct forms of MONITOR
and MWAIT instructions with explicit operands:

  error: invalid operand for instruction
          monitor %rax,%ecx,%edx
                       ^~~~

Use instruction mnemonics with implicit operands when LLVM assembler
is detected to work around this issue.

Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Fixes: cd3b85b27542 ("x86/idle: Use MONITOR and MWAIT mnemonics in <asm/mwait.h>")
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-kbuild-all/202504030802.2lEVBSpN-lkp@xxxxxxxxx/
---
 arch/x86/include/asm/mwait.h | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h
index 5141d2acc0ef..d956d1be4873 100644
--- a/arch/x86/include/asm/mwait.h
+++ b/arch/x86/include/asm/mwait.h
@@ -25,9 +25,18 @@
 #define TPAUSE_C01_STATE		1
 #define TPAUSE_C02_STATE		0
 
+#ifdef CONFIG_LD_IS_LLD
+# define ASM_MONITOR	"monitor"
+# define ASM_MWAIT	"mwait"
+#else
+# define ASM_MONITOR	"monitor %[eax], %[ecx], %[edx]"
+# define ASM_MWAIT	"mwait %[eax], %[ecx]"
+#endif
+
 static __always_inline void __monitor(const void *eax, u32 ecx, u32 edx)
 {
-	asm volatile("monitor %0, %1, %2" :: "a" (eax), "c" (ecx), "d" (edx));
+	asm volatile(ASM_MONITOR
+		     :: [eax] "a" (eax), [ecx] "c" (ecx), [edx] "d" (edx));
 }
 
 static __always_inline void __monitorx(const void *eax, u32 ecx, u32 edx)
@@ -41,7 +50,7 @@ static __always_inline void __mwait(u32 eax, u32 ecx)
 {
 	mds_idle_clear_cpu_buffers();
 
-	asm volatile("mwait %0, %1" :: "a" (eax), "c" (ecx));
+	asm volatile(ASM_MWAIT :: [eax] "a" (eax), [ecx] "c" (ecx));
 }
 
 /*
@@ -92,7 +101,8 @@ static __always_inline void __sti_mwait(u32 eax, u32 ecx)
 {
 	mds_idle_clear_cpu_buffers();
 
-	asm volatile("sti; mwait %0, %1" :: "a" (eax), "c" (ecx));
+	asm volatile("sti\n\t"
+		     ASM_MWAIT :: [eax] "a" (eax), [ecx] "c" (ecx));
 }
 
 /*
-- 
2.49.0