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x86/idle: Use MONITOR and MWAIT mnemonics in <asm/mwait.h>

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Current minimum required version of binutils is 2.25,
which supports MONITOR and MWAIT instruction mnemonics.

Replace the byte-wise specification of MONITOR and
MWAIT with these proper mnemonics.

No functional change intended.

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

  error: invalid operand for instruction
          monitor %rax,%ecx,%edx
                       ^~~~
  # https://lore.kernel.org/oe-kbuild-all/202504030802.2lEVBSpN-lkp@intel.com/

Use instruction mnemonics with implicit operands to
work around this issue.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20250403125111.429805-1-ubizjak@gmail.com
This commit is contained in:
Uros Bizjak 2025-04-03 14:50:45 +02:00 committed by Ingo Molnar
parent a17b37a3f4
commit fc1cd60042
1 changed files with 12 additions and 9 deletions
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21
arch/x86/include/asm/mwait.h
View File

@ -27,9 +27,11 @@
static __always_inline void __monitor(const void *eax, u32 ecx, u32 edx)
{
/* "monitor %eax, %ecx, %edx;" */
asm volatile(".byte 0x0f, 0x01, 0xc8;"
:: "a" (eax), "c" (ecx), "d"(edx));
/*
* Use the instruction mnemonic with implicit operands, as the LLVM
* assembler fails to assemble the mnemonic with explicit operands:
*/
asm volatile("monitor" :: "a" (eax), "c" (ecx), "d" (edx));
}
static __always_inline void __monitorx(const void *eax, u32 ecx, u32 edx)
@ -43,9 +45,11 @@ static __always_inline void __mwait(u32 eax, u32 ecx)
{
mds_idle_clear_cpu_buffers();
/* "mwait %eax, %ecx;" */
asm volatile(".byte 0x0f, 0x01, 0xc9;"
:: "a" (eax), "c" (ecx));
/*
* Use the instruction mnemonic with implicit operands, as the LLVM
* assembler fails to assemble the mnemonic with explicit operands:
*/
asm volatile("mwait" :: "a" (eax), "c" (ecx));
}
/*
@ -95,9 +99,8 @@ static __always_inline void __mwaitx(u32 eax, u32 ebx, u32 ecx)
static __always_inline void __sti_mwait(u32 eax, u32 ecx)
{
mds_idle_clear_cpu_buffers();
/* "mwait %eax, %ecx;" */
asm volatile("sti; .byte 0x0f, 0x01, 0xc9;"
:: "a" (eax), "c" (ecx));
asm volatile("sti; mwait" :: "a" (eax), "c" (ecx));
}
/*