Re: [PATCH] x86/xen: Fix __xen_hypercall_setfunc

From: Juergen Gross
Date: Fri Apr 11 2025 - 03:47:53 EST


On 10.04.25 21:31, Jason Andryuk wrote:
Hypercall detection is failing with xen_hypercall_intel() chosen even on
an AMD processor. Looking at the disassembly, the call to
xen_get_vendor() was removed.

The check for boot_cpu_has(X86_FEATURE_CPUID) was used as a proxy for
the x86_vendor having been set. When
CONFIG_X86_REQUIRED_FEATURE_CPUID=y (the default value), DCE eliminates
the call to xen_get_vendor(). An uninitialized value 0 means
X86_VENDOR_INTEL, so the Intel function is always returned.

Remove the if and always call xen_get_vendor() to avoid this issue.

Fixes: 3d37d9396eb3 ("x86/cpufeatures: Add {REQUIRED,DISABLED} feature configs")
Suggested-by: Juergen Gross <jgross@xxxxxxxx>
Signed-off-by: Jason Andryuk <jason.andryuk@xxxxxxx>

Reviewed-by: Juergen Gross <jgross@xxxxxxxx>


Juergen

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