2016-12-16 16:23:43

by Boris Ostrovsky

Subject: [PATCH] x86/microcode: Use native_cpuid() in load_ucode_amd_bsp()

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 <[email protected]>
---
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

2016-12-16 16:37:40

by Borislav Petkov

Subject: Re: [PATCH] x86/microcode: Use native_cpuid() in load_ucode_amd_bsp()

On Fri, Dec 16, 2016 at 11:39:52AM -0500, Boris Ostrovsky wrote:
> 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 <[email protected]>
> ---
> 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);
> }
> --

Applied, thanks.

--
Regards/Gruss,
Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.