On 10/31/25 15:48, Boris Brezillon wrote:
There's no reason for panthor_vm_[un]map_pages() to fail unless the
drm_gpuvm state and the page table are out of sync, so let's reflect that
by making panthor_vm_unmap_pages() a void function and adding
WARN_ON()s in various places. We also try to recover from those
unexpected mismatch by checking for already unmapped ranges and skipping
them. But there's only so much we can do to try and cope with such
SW bugs, so when we see a mismatch, we flag the VM unusable and disable
the AS to avoid further GPU accesses to the memory.
It could be that the as_disable() call fails because the MMU unit is
stuck, in which case the whole GPU is frozen, and only a GPU reset can
unblock things. Ater the reset, the VM will be seen as unusable and
any attempt to re-use it will fail, so we should be covered for any
use-after-unmap issues.
Signed-off-by: Boris Brezillon <[email protected]>
---
drivers/gpu/drm/panthor/panthor_mmu.c | 82 ++++++++++++++++++---------
1 file changed, 55 insertions(+), 27 deletions(-)
diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c
b/drivers/gpu/drm/panthor/panthor_mmu.c
index ea886c8ac97f..a4f3ed04b5cc 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -846,12 +846,32 @@ static size_t get_pgsize(u64 addr, size_t size, size_t
*count)
return SZ_2M;
}
-static int panthor_vm_unmap_pages(struct panthor_vm *vm, u64 iova, u64 size)
+static void panthor_vm_declare_unusable(struct panthor_vm *vm)
+{
+ struct panthor_device *ptdev = vm->ptdev;
+ int cookie;
+
+ if (vm->unusable)
+ return;
+
+ vm->unusable = true;
+ mutex_unlock(&ptdev->mmu->as.slots_lock);
Please fix this. Need to call mutex_lock.
+ if (vm->as.id >= 0 && drm_dev_enter(&ptdev->base, &cookie)) {
+ panthor_mmu_as_disable(ptdev, vm->as.id);
+ drm_dev_exit(cookie);
+ }
+ mutex_unlock(&ptdev->mmu->as.slots_lock);
+}
+
+static void panthor_vm_unmap_pages(struct panthor_vm *vm, u64 iova, u64 size)
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