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x86/msr: Rename the WRMSRNS opcode macro to ASM_WRMSRNS (for KVM)

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Rename the WRMSRNS instruction opcode macro so that it doesn't collide
with X86_FEATURE_WRMSRNS when using token pasting to generate references
to X86_FEATURE_WRMSRNS.  KVM heavily uses token pasting to generate KVM's
set of support feature bits, and adding WRMSRNS support in KVM will run
will run afoul of the opcode macro.

  arch/x86/kvm/cpuid.c:719:37: error: pasting "X86_FEATURE_" and "" "" does not
                                      give a valid preprocessing token
  719 |         u32 __leaf = __feature_leaf(X86_FEATURE_##name);                \
      |                                     ^~~~~~~~~~~~

KVM has worked around one such collision in the past by #undef'ing the
problematic macro in order to avoid blocking a KVM rework, but such games
are generally undesirable, e.g. requires bleeding macro details into KVM,
risks weird behavior if what KVM is #undef'ing changes, etc.

Reviewed-by: Xin Li (Intel) <xin@zytor.com>
Link: https://lore.kernel.org/r/20250227010111.3222742-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2025-02-26 17:01:10 -08:00
parent 656d9624bd
commit 3fa0fc95db
1 changed files with 2 additions and 2 deletions
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4
arch/x86/include/asm/msr.h
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@ -300,7 +300,7 @@ do { \
#endif /* !CONFIG_PARAVIRT_XXL */
/* Instruction opcode for WRMSRNS supported in binutils >= 2.40 */
#define WRMSRNS _ASM_BYTES(0x0f,0x01,0xc6)
#define ASM_WRMSRNS _ASM_BYTES(0x0f,0x01,0xc6)
/* Non-serializing WRMSR, when available. Falls back to a serializing WRMSR. */
static __always_inline void wrmsrns(u32 msr, u64 val)
@ -309,7 +309,7 @@ static __always_inline void wrmsrns(u32 msr, u64 val)
* WRMSR is 2 bytes. WRMSRNS is 3 bytes. Pad WRMSR with a redundant
* DS prefix to avoid a trailing NOP.
*/
asm volatile("1: " ALTERNATIVE("ds wrmsr", WRMSRNS, X86_FEATURE_WRMSRNS)
asm volatile("1: " ALTERNATIVE("ds wrmsr", ASM_WRMSRNS, X86_FEATURE_WRMSRNS)
"2: " _ASM_EXTABLE_TYPE(1b, 2b, EX_TYPE_WRMSR)
: : "c" (msr), "a" ((u32)val), "d" ((u32)(val >> 32)));
}