From 164a9f712fa53e4c92b2a435bb071a5be0c31dbc Mon Sep 17 00:00:00 2001 From: Jason Andryuk Date: Thu, 10 Apr 2025 15:31:05 -0400 Subject: [PATCH] x86/xen: Fix __xen_hypercall_setfunc() 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 Signed-off-by: Jason Andryuk Signed-off-by: Ingo Molnar Reviewed-by: Juergen Gross Cc: Boris Ostrovsky Cc: "H. Peter Anvin" Cc: "Xin Li (Intel)" Link: https://lore.kernel.org/r/20250410193106.16353-1-jason.andryuk@amd.com --- arch/x86/xen/enlighten.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index 1b7710bd0d05..53282dc7d5ac 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -103,10 +103,6 @@ noinstr void *__xen_hypercall_setfunc(void) void (*func)(void); /* - * Xen is supported only on CPUs with CPUID, so testing for - * X86_FEATURE_CPUID is a test for early_cpu_init() having been - * run. - * * Note that __xen_hypercall_setfunc() is noinstr only due to a nasty * dependency chain: it is being called via the xen_hypercall static * call when running as a PVH or HVM guest. Hypercalls need to be @@ -118,8 +114,7 @@ noinstr void *__xen_hypercall_setfunc(void) */ instrumentation_begin(); - if (!boot_cpu_has(X86_FEATURE_CPUID)) - xen_get_vendor(); + xen_get_vendor(); if ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD || boot_cpu_data.x86_vendor == X86_VENDOR_HYGON))