Re: [Xen-devel] [PATCH] x86, amd_ucode: Safeguard against #GP

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.05.14 at 23:28, <aravind.gopalakrishnan@xxxxxxx> wrote:
> When HW tries to load a corrupted patch, it generates #GP
> and hangs the system. Use wrmsr_safe instead so that we
> fail to load microcode gracefully.
> 
> Example on a Fam15h system-
> (XEN) microcode: CPU0 collect_cpu_info: patch_id=0x6000626
> (XEN) microcode: CPU0 size 7870, block size 2586 offset 76 equivID
> 0x6012 rev 0x6000637
> (XEN) microcode: CPU0 found a matching microcode update with version
> 0x6000637 (current=0x6000626)
> (XEN) traps.c:3073: GPF (0000): ffff82d08016f682 -> ffff82d08022d9f8
> (XEN) microcode: CPU0 update from revision 0x6000637 to 0x6000626 failed
> 
> Signed-off-by: Aravind Gopalakrishnan <aravind.gopalakrishnan@xxxxxxx>
> ---
>  xen/arch/x86/microcode_amd.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/xen/arch/x86/microcode_amd.c b/xen/arch/x86/microcode_amd.c
> index e83f4b6..23637e2 100644
> --- a/xen/arch/x86/microcode_amd.c
> +++ b/xen/arch/x86/microcode_amd.c
> @@ -191,7 +191,7 @@ static int apply_microcode(int cpu)
>  
>      spin_lock_irqsave(&microcode_update_lock, flags);
>  
> -    wrmsrl(MSR_AMD_PATCHLOADER, (unsigned long)hdr);
> +    wrmsr_safe(MSR_AMD_PATCHLOADER, (unsigned long)hdr);

I think you shouldn't ignore the "return" value here.

Also the last quoted log message above has the two revisions
reversed - mind fixing this at the same time?

Jan


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