On Thu, Jan 25, 2024 at 12:27:14PM +0200, Ville Syrjala wrote: > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > On MTL accessing stolen memory via the BARs is somehow borked, > and it can hang the machine. As a workaround let's bypass the > BARs and just go straight to DSMBASE/GSMBASE instead. > > Note that on every other platform this itself would hang the > machine, but on MTL the system firmware is expected to relax > the access permission guarding stolen memory to enable this > workaround, and thus direct CPU accesses should be fine. > > The raw stolen memory areas won't be passed to VMs so we'll > need to risk using the BAR there for the initial setup. Once > command submission is up we should switch to MI_UPDATE_GTT > which at least shouldn't hang the whole machine. > > v2: Don't use direct GSM/DSM access on guests > Add w/a number > v3: Check register 0x138914 to see if pcode did its job > Add some debug prints > > Cc: Paz Zcharya <pazz@xxxxxxxxxxxx> > Cc: Nirmoy Das <nirmoy.das@xxxxxxxxx> > Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> > Reviewed-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx> > Reviewed-by: Radhakrishna Sripada <radhakrishna.sripada@xxxxxxxxx> > Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> Hi Ville, Thank you so much for this incredible series. It solves the issue regarding MTL initial plane readout that Andrzej Hajda and I worked on in https://patchwork.freedesktop.org/patch/570811/?series=127130&rev=2 In addition, it solved the issue with the new GOP. I tested it on two different devices with Meteor Lake and it worked perfectly: no i915 errors, no flickers or observable issues. Tested-by: Paz Zcharya <pazz@xxxxxxxxxxxx>
