[Xen-devel] [PATCH] x86/microcode: Use native_cpuid() in load_ucode_amd_bsp()

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

When CONFIG_PARAVIRT is selected, cpuid() becomes a call. Since
for 32-bit kernels load_ucode_amd_bsp() is executed before paging
is enabled the call cannot be completed (as kernel virtual addresses
are not reachable yet).

Use native_cpuid() instead which is an asm wrapper for CPUID instruction.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
 arch/x86/kernel/cpu/microcode/amd.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/amd.c 
b/arch/x86/kernel/cpu/microcode/amd.c
index 6f353bd..e2d941f 100644
--- a/arch/x86/kernel/cpu/microcode/amd.c
+++ b/arch/x86/kernel/cpu/microcode/amd.c
@@ -297,6 +297,7 @@ void __init load_ucode_amd_bsp(unsigned int family)
        struct cpio_data cp;
        const char *path;
        bool use_pa;
+       u32 eax, ebx, ecx, edx;
 
        if (IS_ENABLED(CONFIG_X86_32)) {
                uci     = (struct ucode_cpu_info *)__pa_nodebug(ucode_cpu_info);
@@ -315,7 +316,10 @@ void __init load_ucode_amd_bsp(unsigned int family)
                return;
 
        /* Get BSP's CPUID.EAX(1), needed in load_microcode_amd() */
-       uci->cpu_sig.sig = cpuid_eax(1);
+       eax = 0x00000001;
+       ecx = 0;
+       native_cpuid(&eax, &ebx, &ecx, &edx);
+       uci->cpu_sig.sig = eax;
 
        apply_microcode_early_amd(cp.data, cp.size, true);
 }
-- 
1.7.1


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