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From: "tip-bot2 for Uros Bizjak" <tip-bot2@linutronix.de>
Sender: tip-bot2@linutronix.de
Reply-to: linux-kernel@vger.kernel.org
To: linux-tip-commits@vger.kernel.org
Subject:
[tip: x86/mm] x86/idle: Use MONITOR and MWAIT mnemonics in <asm/mwait.h>
Cc: kernel test robot <lkp@intel.com>, Uros Bizjak <ubizjak@gmail.com>,
Ingo Molnar <mingo@kernel.org>, "Borislav Petkov (AMD)" <bp@alien8.de>,
x86@kernel.org, linux-kernel@vger.kernel.org
In-Reply-To: <20250403125111.429805-1-ubizjak@gmail.com>
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The following commit has been merged into the x86/mm branch of tip:
Commit-ID: defea9e60d3f440ca8da070a478f668fec0ba659
Gitweb: https://git.kernel.org/tip/defea9e60d3f440ca8da070a478f668fe=
c0ba659
Author: Uros Bizjak <ubizjak@gmail.com>
AuthorDate: Thu, 03 Apr 2025 14:50:45 +02:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Thu, 03 Apr 2025 15:27:50 +02:00
x86/idle: Use MONITOR and MWAIT mnemonics in <asm/mwait.h>
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.c=
om/
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
---
arch/x86/include/asm/mwait.h | 17 ++++++++---------
1 file changed, 8 insertions(+), 9 deletions(-)
diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h
index 6a2ec20..26b68ee 100644
--- a/arch/x86/include/asm/mwait.h
+++ b/arch/x86/include/asm/mwait.h
@@ -27,9 +27,9 @@
=20
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));
}
=20
static __always_inline void __monitorx(const void *eax, u32 ecx, u32 edx)
@@ -43,9 +43,9 @@ static __always_inline void __mwait(u32 eax, u32 ecx)
{
mds_idle_clear_cpu_buffers();
=20
- /* "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));
}
=20
/*
@@ -95,9 +95,8 @@ static __always_inline void __mwaitx(u32 eax, u32 ebx, u3=
2 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));
}
=20
/*