Re: [PATCH] vfio: pci: use kzalloc_flex

Gustavo A. R. Silva
2026-03-30T23:47:43Z

On 3/30/26 17:24, Rosen Penev wrote:
> On Mon, Mar 30, 2026 at 4:16 PM Alex Williamson <alex@shazbot.org> wrote:
>>
>> [Cc +Leon]
>>
>> On Wed, 25 Mar 2026 19:37:47 -0700
>> Rosen Penev <rosenp@gmail.com> wrote:
>>
>>> Simplify allocation by using a flexible array member and kzalloc_flex.
>>> Less memory management needed.
>>>
>>> Use __counted_by for extra runtime analysis. Move assignment to after
>>> allocation as required by __counted_by.
>>
>> I don't understand this statement, nr_ranges was previously set after
>> the allocation of phys_vec. The only reordering was relative to
>> setting vdev, but that appears arbitrary.
> Yes that one. My understanding is __counted_by mandates immediate
> assignment after allocation. Otherwise UBSAN complains.

Not true. However, it's best practice.

The requirement is that the _counter_ must be initialized before
the first reference to the flexible-array member.

-Gustavo