Re: [PATCH RESEND] drm/virtio: Align host mapping request to maximum platform page size

[Dmitry Osipenko <dmitry.osipenko@collabora.com>]

On 1/25/25 01:58, Sasha Finkelstein wrote:
> On Fri, 24 Jan 2025 at 23:52, Dmitry Osipenko
> <dmitry.osipenko@collabora.com> wrote:
>>> -     ret = drm_mm_insert_node(&vgdev->host_visible_mm, &vram->vram_node,
>>> -                              bo->base.base.size);
>>> +     ret = drm_mm_insert_node_generic(&vgdev->host_visible_mm, &vram->vram_node,
>>> +                                      bo->base.base.size, MAX_PAGE_SIZE, 0, 0);
>>
>> This change only reserves extra space in the memory allocator, but
>> doesn't change actual size of allocated BO. Instead, you likely need to
>> replace all ALIGN(size, PAGE_SIZE) occurrences in the driver code with
>> ALIGN(args->size, MAX_PAGE_SIZE)
> 
> This approach is good enough for my usecase, where the vmm can
> cope with sub-page gpu allocations (by rounding up to full page),
> but can't deal with non page aligned ones.

Driver should work properly with any VMM. Aligning BO size will work
universally, but then you could do it too in a userspace.

-- 
Best regards,
Dmitry