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

mainline inclusion
from mainline-v5.4-rc1
commit f71da467
category: bugfix
bugzilla: 21306
CVE: NA

-------------------------------------------------------------------------

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: NWill Deacon <will@kernel.org>
Signed-off-by: NZhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: NHanjun Guo <guohanjun@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>

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

@@ -598,7 +598,6 @@ 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

@@ -527,7 +527,6 @@ 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;
 	}