From: Robin Murphy robin.murphy@arm.com
[ Upstream commit 85c7a0f1ef624ef58173ef52ea77780257bdfe04 ]
In removing the pagetable-wide lock, we gained the possibility of the vanishingly unlikely case where we have a race between two concurrent unmappers splitting the same block entry. The logic to handle this is fairly straightforward - whoever loses the race frees their partial next-level table and instead dereferences the winner's newly-installed entry in order to fall back to a regular unmap, which intentionally echoes the pre-existing case of recursively splitting a 1GB block down to 4KB pages by installing a full table of 2MB blocks first.
Unfortunately, the chump who implemented that logic failed to update the condition check for that fallback, meaning that if said race occurs at the last level (where the loser's unmap_idx is valid) then the unmap won't actually happen. Fix that to properly account for both the race and recursive cases.
Fixes: 2c3d273eabe8 ("iommu/io-pgtable-arm: Support lockless operation") Signed-off-by: Robin Murphy robin.murphy@arm.com [will: re-jig control flow to avoid duplicate cmpxchg test] Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/iommu/io-pgtable-arm.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c index 88641b4560bc8..2f79efd16a052 100644 --- a/drivers/iommu/io-pgtable-arm.c +++ b/drivers/iommu/io-pgtable-arm.c @@ -574,13 +574,12 @@ static size_t arm_lpae_split_blk_unmap(struct arm_lpae_io_pgtable *data, return 0;
tablep = iopte_deref(pte, data); + } else if (unmap_idx >= 0) { + io_pgtable_tlb_add_flush(&data->iop, iova, size, size, true); + return size; }
- if (unmap_idx < 0) - return __arm_lpae_unmap(data, iova, size, lvl, tablep); - - io_pgtable_tlb_add_flush(&data->iop, iova, size, size, true); - return size; + return __arm_lpae_unmap(data, iova, size, lvl, tablep); }
static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data,