Re: [Intel-gfx] [PATCH 00/10] Connect VFIO to IOMMUFD

Jason Gunthorpe
2022-10-31T12:18:52Z

On Mon, Oct 31, 2022 at 06:38:45PM +0800, Yi Liu wrote:
> Hi Jason,
>
> On 2022/10/26 02:17, Jason Gunthorpe wrote:
> > This series provides an alternative container layer for VFIO implemented
> > using iommufd. This is optional, if CONFIG_IOMMUFD is not set then it will
> > not be compiled in.
> >
> > At this point iommufd can be injected by passing in a iommfd FD to
> > VFIO_GROUP_SET_CONTAINER which will use the VFIO compat layer in iommufd
> > to obtain the compat IOAS and then connect up all the VFIO drivers as
> > appropriate.
> >
> > This is temporary stopping point, a following series will provide a way to
> > directly open a VFIO device FD and directly connect it to IOMMUFD using
> > native ioctls that can expose the IOMMUFD features like hwpt, future
> > vPASID and dynamic attachment.
> >
> > This series, in compat mode, has passed all the qemu tests we have
> > available, including the test suites for the Intel GVT mdev. Aside from
> > the temporary limitation with P2P memory this is belived to be fully
> > compatible with VFIO.
> >
> > This is on github: https://github.com/jgunthorpe/linux/commits/vfio_iommufd
>
> In our side, we found the gvt-g test failed. Guest i915 driver stuck at
> init phase. While with your former version (commit ID
> a249441ba6fd9d658f4a1b568453e3a742d12686), gvt-g test is passing.

Oh, I didn't realize you grabbed such an older version for this testing..

> noticed there a quite a few change in iommufd/pages.c from last version.
> We are internally tracing in the gvt-g side, may also good to have your
> attention.

syzkaller just ran into this that I was starting to investigate:

@@ -1505,7 +1505,7 @@ int iopt_pages_fill_xarray(struct iopt_pages *pages, unsigned long start_index,
int rc;

pfn_reader_user_init(&user, pages);
- user.upages_len = last_index - start_index + 1;
+ user.upages_len = (last_index - start_index + 1) * sizeof(*out_pages);
interval_tree_for_each_double_span(&span, &pages->access_itree,

It would certainly hit gvt - but you should get WARN_ON's not hangs

There is something wrong with the test suite that it isn't covering
the above, I'm going to look into that today.

Jason