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Re: [PATCH v2 1/5] x86: Update x86 low level version check of microcode


  • To: Fouad Hilly <fouad.hilly@xxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Mon, 22 Apr 2024 16:09:35 +0200
  • Autocrypt: addr=jbeulich@xxxxxxxx; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL
  • Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Mon, 22 Apr 2024 14:09:45 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 16.04.2024 11:15, Fouad Hilly wrote:
> Update microcode version check at Intel and AMD Level by:
> Preventing the low level code from sending errors if the microcode
> version provided is not a newer version.

And why is this change (a) wanted and (b) correct?

> Other errors will be sent like before.
> When the provided microcode version is the same as the current one, code
> to point to microcode provided.

I'm afraid I can't interpret this sentence.

> Microcode version check happens at higher and common level in core.c.
> Keep all the required code at low level that checks for signature and CPU 
> compatibility
> 
> [v2]
> Update message description to better describe the changes

This belongs ...

> Signed-off-by: Fouad Hilly <fouad.hilly@xxxxxxxxx>
> ---

... below the separator.

> --- a/xen/arch/x86/cpu/microcode/amd.c
> +++ b/xen/arch/x86/cpu/microcode/amd.c
> @@ -383,12 +383,8 @@ static struct microcode_patch *cf_check 
> cpu_request_microcode(
>                  goto skip;
>              }
>  
> -            /*
> -             * If the new ucode covers current CPU, compare ucodes and store 
> the
> -             * one with higher revision.
> -             */
> -            if ( (microcode_fits(mc->patch) != MIS_UCODE) &&
> -                 (!saved || (compare_header(mc->patch, saved) == NEW_UCODE)) 
> )
> +            /* If the provided ucode covers current CPU, then store its 
> revision. */
> +            if ( (microcode_fits(mc->patch) != MIS_UCODE) && !saved )
>              {
>                  saved = mc->patch;
>                  saved_size = mc->len;
> --- a/xen/arch/x86/cpu/microcode/intel.c
> +++ b/xen/arch/x86/cpu/microcode/intel.c
> @@ -294,8 +294,7 @@ static int cf_check apply_microcode(const struct 
> microcode_patch *patch)
>  
>      result = microcode_update_match(patch);
>  
> -    if ( result != NEW_UCODE &&
> -         !(opt_ucode_allow_same && result == SAME_UCODE) )
> +    if ( result != NEW_UCODE && result != SAME_UCODE )
>          return -EINVAL;

Unlike the other two adjustments this one results in still permitting
only same-or-newer. How does this fit with the AMD change above and
the other Intel change ...

> @@ -354,12 +353,8 @@ static struct microcode_patch *cf_check 
> cpu_request_microcode(
>          if ( error )
>              break;
>  
> -        /*
> -         * If the new update covers current CPU, compare updates and store 
> the
> -         * one with higher revision.
> -         */
> -        if ( (microcode_update_match(mc) != MIS_UCODE) &&
> -             (!saved || compare_revisions(saved->rev, mc->rev) == NEW_UCODE) 
> )
> +        /* If the provided ucode covers current CPU, then store its 
> revision. */
> +        if ( (microcode_update_match(mc) != MIS_UCODE) && !saved )
>              saved = mc;

... here?

Jan



 


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