[PATCH v2 2/3] x86/cpuid: fix unbootable VMs by really inlining memcmp() in hypervisor_cpuid_base()

[Mauricio Faria de Oliveira <mfo@igalia.com>]

Even with __builtin the compiler may decide to use the out of line function
instead of the inline implementation.

The existing code is broken with gcc-14/15 but not gcc-12/13 (Ubuntu 25.10)
and vmlinux no longer boots with CONFIG_PVH if CONFIG_KASAN_GENERIC is set.

For testing purposes, if the size argument is reduced from 12 to 8 then the
compiler decides to use the inline implementation; that shows results vary.

Switch the builtin to the inline implementation to address it.

Fixes: 416a33c9afce ("x86/cpu: fix unbootable VMs by inlining memcmp() in hypervisor_cpuid_base()")
Signed-off-by: Mauricio Faria de Oliveira <mfo@igalia.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
---
 arch/x86/include/asm/cpuid/api.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/cpuid/api.h b/arch/x86/include/asm/cpuid/api.h
index 44fa82e1267ce98c7f5f92f69b58f79e235f7261..c3bd1e51067346e817240b484dc0d0e5f02dcc4f 100644
--- a/arch/x86/include/asm/cpuid/api.h
+++ b/arch/x86/include/asm/cpuid/api.h
@@ -203,7 +203,7 @@ static inline u32 cpuid_base_hypervisor(const char *sig, u32 leaves)
 		 * from PVH early boot code before instrumentation is set up
 		 * and memcmp() itself may be instrumented.
 		 */
-		if (!__builtin_memcmp(sig, signature, 12) &&
+		if (!__inline_memcmp(sig, signature, 12) &&
 		    (leaves == 0 || ((eax - base) >= leaves)))
 			return base;
 	}

-- 
2.51.0