Commit f71da467 authored Jul 02, 2019 by Will Deacon

iommu/io-pgtable-arm: Remove redundant call to io_pgtable_tlb_sync()



Commit b6b65ca2 ("iommu/io-pgtable-arm: Add support for non-strict
mode") added an unconditional call to io_pgtable_tlb_sync() immediately
after the case where we replace a block entry with a table entry during
an unmap() call. This is redundant, since the IOMMU API will call
iommu_tlb_sync() on this path and the patch in question mentions this:

 | To save having to reason about it too much, make sure the invalidation
 | in arm_lpae_split_blk_unmap() just performs its own unconditional sync
 | to minimise the window in which we're technically violating the break-
 | before-make requirement on a live mapping. This might work out redundant
 | with an outer-level sync for strict unmaps, but we'll never be splitting
 | blocks on a DMA fastpath anyway.

However, this sync gets in the way of deferred TLB invalidation for leaf
entries and is at best a questionable, unproven hack. Remove it.

Signed-off-by: Will Deacon <will@kernel.org>

parent 6d1bcb95

drivers/iommu/io-pgtable-arm-v7s.c

+0 −1

Original line number	Diff line number	Diff line
		@@ -587,7 +587,6 @@ static size_t arm_v7s_split_blk_unmap(struct arm_v7s_io_pgtable *data,
		}

		io_pgtable_tlb_add_flush(&data->iop, iova, size, size, true);
		io_pgtable_tlb_sync(&data->iop);
		return size;
		}

drivers/iommu/io-pgtable-arm.c

+0 −1

Original line number	Diff line number	Diff line
		@@ -583,7 +583,6 @@ static size_t arm_lpae_split_blk_unmap(struct arm_lpae_io_pgtable *data,
		tablep = iopte_deref(pte, data);
		} else if (unmap_idx >= 0) {
		io_pgtable_tlb_add_flush(&data->iop, iova, size, size, true);
		io_pgtable_tlb_sync(&data->iop);
		return size;
		}

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