[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [PATCH 08/10] x86/ucode: Use bootstrap_unmap() in early_microcode_load()


  • To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Mon, 28 Oct 2024 16:38:28 +0100
  • 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: Roger Pau Monné <roger.pau@xxxxxxxxxx>, "Daniel P . Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Mon, 28 Oct 2024 15:38:32 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 28.10.2024 10:18, Andrew Cooper wrote:
> If bootstrap_map() has provided a mapping, we must free it when done.  Failing
> to do so may cause a spurious failure for unrelated logic later.
> 
> Inserting a bootstrap_unmap() here does not break the use of ucode_{blob,mod}
> any more than they already are.
> 
> Add a printk noting when we didn't find a microcode patch.  It's at debug
> level, because this is the expected case on AMD Client systems, and SDPs, but
> for people trying to figure out why microcode loading isn't work, it might be
> helpful.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Hmm, yes, I think this is correct now (but the mapping had to persist earlier
on, likely years ago). So
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
However, as a nit, ...

> --- a/xen/arch/x86/cpu/microcode/core.c
> +++ b/xen/arch/x86/cpu/microcode/core.c
> @@ -823,6 +823,7 @@ static int __init early_microcode_load(struct boot_info 
> *bi)
>      size_t size;
>      struct microcode_patch *patch;
>      int idx = opt_mod_idx;
> +    int rc = 0;

... the initializer doesn't appear to be needed here; all paths ...

> @@ -878,15 +879,24 @@ static int __init early_microcode_load(struct boot_info 
> *bi)
>      patch = ucode_ops.cpu_request_microcode(data, size, false);
>      if ( IS_ERR(patch) )
>      {
> -        printk(XENLOG_WARNING "Parsing microcode blob error %ld\n",
> -               PTR_ERR(patch));
> -        return PTR_ERR(patch);
> +        rc = PTR_ERR(patch);
> +        printk(XENLOG_WARNING "Microcode: Parse error %d\n", rc);
> +        goto unmap;
>      }
>  
>      if ( !patch )
> -        return -ENOENT;
> +    {
> +        printk(XENLOG_DEBUG "Microcode: No suitable patch found\n");
> +        rc = -ENOENT;
> +        goto unmap;
> +    }
> +
> +    rc = microcode_update_cpu(patch, 0);
>  
> -    return microcode_update_cpu(patch, 0);
> + unmap:
> +    bootstrap_unmap();
> +
> +    return rc;
>  }

... reliably set the variable. (I don't recall what our conclusion was as to
Misra possibly considering such unnecessary initializers dead code.)

Jan



 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.