Xen devel - Oct 2011 - Re: [PATCH] x86/ucode-amd: fix regression from c/s 23871:503ee25

On 21/10/2011 09:37, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:
> microcode_fits() must return distinct values for the success and
> no-fit-but-no-error cases, so the caller can react accordingly. Make
> it return 1 in the success case, and adjust its single caller.
> 
> Also remove an impossible code path - install_equiv_cpu_table(), which
> gets called prior to microcode_fits(), never leaves equiv_cpu_table
> being NULL without also returning an error.
> 
> Note that this is still awaiting testing on a system where the
> regression was actually observed (which also requires a new enough
> microcode_ctl package). Note also that this will need to be
> backported to 4.0 and 4.1 (or the broken c/s that got backported
> there reverted).
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
> 
> --- a/xen/arch/x86/microcode_amd.c
> +++ b/xen/arch/x86/microcode_amd.c
> @@ -76,14 +76,6 @@ static int microcode_fits(void *mc, int 
>      /* We should bind the task to the CPU */
>      BUG_ON(cpu != raw_smp_processor_id());
>  
> -    if ( equiv_cpu_table == NULL )
> -    {
> -        printk(KERN_INFO "microcode: CPU%d microcode update with
"
> -               "version 0x%x (current=0x%x)\n",
> -               cpu, mc_header->patch_id, uci->cpu_sig.rev);
> -        goto out;
> -    }
> -
>      current_cpu_id = cpuid_eax(0x00000001);
>  
>      for ( i = 0; equiv_cpu_table[i].installed_cpu != 0; i++ )
> @@ -96,7 +88,7 @@ static int microcode_fits(void *mc, int 
>      }
>  
>      if ( !equiv_cpu_id )
> -           return 0;
> +        return 0;
>  
>      if ( (mc_header->processor_rev_id) != equiv_cpu_id )
>      {
> @@ -113,8 +105,7 @@ static int microcode_fits(void *mc, int 
>             "update with version 0x%x (current=0x%x)\n",
>             cpu, mc_header->patch_id, uci->cpu_sig.rev);
>  
> -out:
> -    return 0;
> +    return 1;
>  }
>  
>  static int apply_microcode(int cpu)
> @@ -285,7 +276,7 @@ static int cpu_request_microcode(int cpu
>      while ( (ret = get_next_ucode_from_buffer_amd(mc, buf, size,
&offset))
> == 
> 0)
>      {
>          error = microcode_fits(mc, cpu);
> -        if (error != 0)
> +        if (error <= 0)
>              continue;
>  
>          error = apply_microcode(cpu);
> 
Our internal testing confirms that this patch fixes the boot problem.  
Comment from Bugzilla states,
"Both affected systems (with most recent microcode_ctl-1.17-102.38.1
installed
and insserv''ed) are now booting well."

- Charles



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