On 05/09/2024 4:53 pm, Will Deacon wrote:
Hi Rob,
On Thu, Sep 05, 2024 at 05:49:56AM -0700, Rob Clark wrote:
From: Rob Clark <robdclark@xxxxxxxxxxxx>
This reverts commit 85b715a334583488ad7fbd3001fe6fd617b7d4c0.
It was causing gpu smmu faults on x1e80100.
I _think_ what is causing this is the change in ordering of
__arm_lpae_clear_pte() (dma_sync_single_for_device() on the pgtable
memory) and io_pgtable_tlb_flush_walk(). I'm not entirely sure how
this patch is supposed to work correctly in the face of other
concurrent translations (to buffers unrelated to the one being
unmapped(), because after the io_pgtable_tlb_flush_walk() we can have
stale data read back into the tlb.
Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
---
drivers/iommu/io-pgtable-arm.c | 31 ++++++++++++++-----------------
1 file changed, 14 insertions(+), 17 deletions(-)
Please can you try the diff below, instead?
Given that the GPU driver's .tlb_add_page is a no-op, I can't see this
making a difference. In fact, given that msm_iommu_pagetable_unmap()
still does a brute-force iommu_flush_iotlb_all() after io-pgtable
returns, and in fact only recently made .tlb_flush_walk start doing
anything either for the sake of the map path, I'm now really wondering
how this patch has had any effect at all... :/
Will
--->8
diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index 0e67f1721a3d..0a32e9499e2c 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -672,7 +672,7 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data,
/* Clear the remaining entries */
__arm_lpae_clear_pte(ptep, &iop->cfg, i);
- if (gather && !iommu_iotlb_gather_queued(gather))
+ if (!iommu_iotlb_gather_queued(gather))
Note that this would reintroduce the latent issue which was present
originally, wherein iommu_iotlb_gather_queued(NULL) is false, but if we
actually allow a NULL gather to be passed to io_pgtable_tlb_add_page()
it may end up being dereferenced (e.g. in arm-smmu-v3).
Thanks,
Robin.
for (int j = 0; j < i; j++)
io_pgtable_tlb_add_page(iop, gather, iova + j * size, size);
