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Re: [PATCH v6] xen/console: introduce domain_console struct


  • To: dmkhn@xxxxxxxxx
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Fri, 11 Jul 2025 12:12:01 +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.cooper3@xxxxxxxxxx, anthony.perard@xxxxxxxxxx, julien@xxxxxxx, michal.orzel@xxxxxxx, roger.pau@xxxxxxxxxx, sstabellini@xxxxxxxxxx, dmukhin@xxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx
  • Delivery-date: Fri, 11 Jul 2025 10:12:23 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 11.07.2025 09:25, dmkhn@xxxxxxxxx wrote:
> On Fri, Jul 11, 2025 at 07:59:27AM +0200, Jan Beulich wrote:
>> On 11.07.2025 03:07, dmkhn@xxxxxxxxx wrote:
>>> On Thu, Jul 10, 2025 at 01:16:24PM +0200, Jan Beulich wrote:
>>>> On 10.07.2025 03:35, dmkhn@xxxxxxxxx wrote:
>>>>> @@ -877,6 +873,16 @@ struct domain *domain_create(domid_t domid,
>>>>>
>>>>>      /* All error paths can depend on the above setup. */
>>>>>
>>>>> +    BUILD_BUG_ON(DOMAIN_CONSOLE_BUF_SIZE <= 0);
>>>>
>>>> While the "equals 0" case can in principle happen, the "less than" part
>>>> is dead code (and hence this needs checking differently): The type of
>>>> DOMAIN_CONSOLE_BUF_SIZE is an unsigned one, so wrapping through 0 will
>>>> yield huge positive values.
>>>>
>>>>> +    err = -ENOMEM;
>>>>> +    d->console = xzalloc_bytes(DOMAIN_CONSOLE_SIZE);
>>>>
>>>> As previously indicated, new code ought to use the xv*alloc family of
>>>> functions, which deliberately doesn't include any ..._bytes() forms.
>>>> Note how instead there is xvzalloc_flex_struct() for situations like
>>>> the one here.
>>>
>>> Looks like xvzalloc_flex_struct() is not used anywhere in the code base...
>>
>> And what do you mean to tell me by that? xvmalloc_flex_struct() is used,
>> and x[mz]alloc_flex_struct() uses are still in need of conversion (which
>> is going to be a slow-going process).
> 
> Just an observation; I was not aware of these APIs and I was not aware that
> there's some slow-going process of switching to preferred use of
> xvzalloc_flex_struct().

The ongoing conversion is (more generally) from x[mz]alloc family of functions
to the xv[mz]alloc one, as is made explicit by the comment near the top of
xvmalloc.h.

Jan



 


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