On 2/26/2025 5:01 PM, Sean Christopherson wrote:
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.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/include/asm/msr.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 001853541f1e..60b80a36d045 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -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)));
}
I hit the same build issue, thanks for fixing it.
Reviewed-by: Xin Li (Intel) <xin@xxxxxxxxx>
