On Thu, Sep 24, 2026 at 02:30:45PM +0200, Boris Brezillon wrote: > Right now, there's a theoretical window during which the GPU can populate > the cache with data from a VM that's about to be evicted through the > UPDATE(UNMAPPED) command. > In practice this won't happen (hence the absence of Fixes tag) because > when panthor_mmu_as_disable() is called, the VM is guaranteed to be idle > (no active CSG pointing to this VM), but as we say, better safe than > sorry. > > Signed-off-by: Boris Brezillon <[email protected]>
Reviewed-by: Liviu Dudau <[email protected]> Best regards, Liviu > --- > drivers/gpu/drm/panthor/panthor_mmu.c | 19 ++++++++++++------- > 1 file changed, 12 insertions(+), 7 deletions(-) > > diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c > b/drivers/gpu/drm/panthor/panthor_mmu.c > index 038a092fd08c..bb71274aa36b 100644 > --- a/drivers/gpu/drm/panthor/panthor_mmu.c > +++ b/drivers/gpu/drm/panthor/panthor_mmu.c > @@ -631,12 +631,6 @@ static int panthor_mmu_as_disable(struct panthor_device > *ptdev, u32 as_nr) > panthor_mmu_irq_disable_events(&ptdev->mmu->irq, > panthor_mmu_as_fault_mask(ptdev, as_nr)); > > - /* Flush+invalidate RW caches, invalidate RO ones. */ > - ret = panthor_gpu_flush_caches(ptdev, CACHE_CLEAN | CACHE_INV, > - CACHE_CLEAN | CACHE_INV, 0); > - if (ret) > - return ret; > - > if (vm && vm->locked_region.size) { > /* Unlock the region if there's a lock pending. */ > ret = as_send_cmd_and_wait(ptdev, vm->as.id, AS_COMMAND_UNLOCK); > @@ -648,7 +642,18 @@ static int panthor_mmu_as_disable(struct panthor_device > *ptdev, u32 as_nr) > gpu_write64(mmu->iomem, AS_MEMATTR(as_nr), 0); > gpu_write64(mmu->iomem, AS_TRANSCFG(as_nr), > AS_TRANSCFG_ADRMODE_UNMAPPED); > > - return as_send_cmd_and_wait(ptdev, as_nr, AS_COMMAND_UPDATE); > + ret = as_send_cmd_and_wait(ptdev, as_nr, AS_COMMAND_UPDATE); > + if (ret) > + return ret; > + > + /* Flush+invalidate RW caches after we've unmapped, to make sure any > + * cacheline eviction is effective before we potentially return > + * memory pointed by this VM to the system. This needs to be done > + * after the UPDATE(UNMAPPED) operation to guarantee that not further > + * PT-walk can pull VM data into the cache. > + */ > + return panthor_gpu_flush_caches(ptdev, CACHE_CLEAN | CACHE_INV, > + CACHE_CLEAN | CACHE_INV, 0); > } > > static u32 panthor_mmu_fault_mask(struct panthor_device *ptdev, u32 value) > > -- > 2.55.0 > -- ==================== | I would like to | | fix the world, | | but they're not | | giving me the | \ source code! / --------------- ¯\_(ツ)_/¯
