Re: [PATCH v8 00/11] Support blob memory and venus on qemu

["Alex Bennée" <alex.bennee@linaro.org>]

Dmitry Osipenko <dmitry.osipenko@collabora.com> writes:

> Hello,
>
> This series enables Vulkan Venus context support on virtio-gpu.
>
> All virglrender and almost all Linux kernel prerequisite changes
> needed by Venus are already in upstream. For kernel there is a pending
> KVM patchset that fixes mapping of compound pages needed for DRM drivers
> using TTM [1], othewrwise hostmem blob mapping will fail with a KVM error
> from Qemu.
>
> [1]
> https://lore.kernel.org/kvm/20240229025759.1187910-1-stevensd@google.com/

Following the link for the TTM/KVM patches on the kernel side points at
changes for AMD cards getting NAK'ed so I'm a little confused as to what
parts are needed.

Is this only relevant for ensuring the virtual mappings to the
underlying hardware aren't moved around when KVM is exporting those
pages to the guest?

Our interest is in Xen which obviously mediates everything through stage
2 mappings to from the real PA to the IPA the domains see. However AIUI
all the blob allocation is managed by the GEM/TTM layer of whichever
kernel is responsible for driving the GPU. Does this layer work with
kernel vaddr or the underlying IPA of the resources? We shouldn't
expect the IPA to change between allocations should we?

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro