On 2021/5/19 2:58, Alex Williamson wrote:

On Fri, 9 Apr 2021 11:44:19 +0800
Shenming Lu [off-list ref] wrote:

quoted

Some devices only allow selective DMA faulting. Similar to the selective
dirty page tracking, the vendor driver can call vfio_pin_pages() to
indicate the non-faultable scope, we add a new struct vfio_range to
record it, then when the IOPF handler receives any page request out
of the scope, we can directly return with an invalid response.

Seems like this highlights a deficiency in the design, that the user
can't specify mappings as iopf enabled or disabled.  Also, if the
vendor driver has pinned pages within the range, shouldn't that prevent
them from faulting in the first place?  Why do we need yet more
tracking structures?  Pages pinned by the vendor driver need to count
against the user's locked memory limits regardless of iopf.  Thanks,

Currently we only have a vfio_pfn struct to track the external pinned pages
(single page granularity), so I add a vfio_range struct for efficient lookup.

Yeah, by this patch, for the non-pinned scope, we can directly return INVALID,
but for the pinned(non-faultable) scope, tracking the pinned range doesn't seem
to help more...

Thanks,
Shenming

Alex

.

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