Re: [PATCH v2 1/4] drm/xe/xe_migrate: Align MEM_COPY pitch with destination address

[Jan Maslak <jan.maslak@intel.com>]

On Mon, Aug 17, 2026 at 05:39:29PM +0100, Matthew Auld wrote:
> On 22/06/2026 11:34, Jan Maslak wrote:
> > From: Christoph Manszewski <christoph.manszewski@intel.com>
> > 
> > MEM_COPY_CMD can corrupt memory when MATRIX_COPY mode uses a pitch that
> > is not aligned to the destination address.
> > 
> > Fix this by incorporating the destination address into the pitch
> > selection so the chosen pitch is aligned to both the copy length and the
> > destination address.
> 
> Should we play it safe and apply this to the src addr also, even if it
> appears to work without? The spec doesn't explicitly state that the dst
> needed this special treatment, but if it does then I would think src would
> be the same?
 
I characterized MEM_COPY across many configurations, including cases where
only the source address was misaligned. Source-address alignment did not
appear to affect the behavior: the corruption required a sufficiently tall
matrix copy and a destination address not aligned to the pitch.
Unfortunately, the specification does not document this restriction.

Since including the source address could unnecessarily reduce the selected
pitch, I'd prefer to keep the workaround limited to the condition we
observed, unless you see another reason to handle both.