Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx> writes: > On 7/23/24 14:49, Sergio Lopez wrote: >> There's an incresing number of machines supporting multiple page sizes >> and on these machines the host and a guest can be running, each one, >> with a different page size. >> >> For what pertains to virtio-gpu, this is not a problem if the page size >> of the guest happens to be bigger or equal than the host, but will >> potentially lead to failures in memory allocations and/or mappings >> otherwise. > > Please describe concrete problem you're trying to solve. Guest memory > allocation consists of guest pages, I don't see how knowledge of host > page size helps anything in userspace. > > I suspect you want this for host blobs, but then it should be > virtio_gpu_vram_create() that should use max(host_page_sz, > guest_page_size), AFAICT. It's kernel who is responsible for memory > management, userspace can't be trusted for doing that. Mesa's Vulkan/Venus uses CREATE_BLOB to request the host the creation and mapping into the guest of device-backed memory and shmem regions. The CREATE_BLOB ioctl doesn't update drm_virtgpu_resource_create->size, so the guest kernel (and, as a consequence, the host kernel) can't override the user's request. I'd like Mesa's Vulkan/Venus in the guest to be able to obtain the host page size to align the size of the CREATE_BLOB requests as required. Thanks, Sergio.
