From: Will Deacon <will@kernel.org>
To: iommu@lists.linux-foundation.org
Cc: Vijay Kilary <vkilari@codeaurora.org>,
Jean-Philippe Brucker <jean-philippe.brucker@arm.com>,
Will Deacon <will@kernel.org>, Jan Glauber <jglauber@marvell.com>,
Alex Williamson <alex.williamson@redhat.com>,
Jayachandran Chandrasekharan Nair <jnair@marvell.com>,
Jon Masters <jcm@redhat.com>, Robin Murphy <robin.murphy@arm.com>
Subject: [RFC PATCH v2 02/19] iommu/io-pgtable-arm: Remove redundant call to io_pgtable_tlb_sync()
Date: Thu, 11 Jul 2019 18:19:10 +0100 [thread overview]
Message-ID: <20190711171927.28803-3-will@kernel.org> (raw)
In-Reply-To: <20190711171927.28803-1-will@kernel.org>
Commit b6b65ca20bc9 ("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>
---
drivers/iommu/io-pgtable-arm-v7s.c | 1 -
drivers/iommu/io-pgtable-arm.c | 1 -
2 files changed, 2 deletions(-)
diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c
index 35de9ebb500c..6a6d6bb438d9 100644
--- a/drivers/iommu/io-pgtable-arm-v7s.c
+++ b/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;
}
diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index b4e624afd1bb..b696b6c139cc 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -594,7 +594,6 @@ 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;
}
--
2.11.0
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next prev parent reply other threads:[~2019-07-11 17:29 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-11 17:19 [RFC PATCH v2 00/19] Try to reduce lock contention on the SMMUv3 command queue Will Deacon
2019-07-11 17:19 ` [RFC PATCH v2 01/19] iommu: Remove empty iommu_tlb_range_add() callback from iommu_ops Will Deacon
2019-07-11 17:19 ` Will Deacon [this message]
2019-07-11 17:19 ` [RFC PATCH v2 03/19] iommu/io-pgtable: Rename iommu_gather_ops to iommu_flush_ops Will Deacon
2019-07-11 17:19 ` [RFC PATCH v2 04/19] iommu: Introduce struct iommu_iotlb_gather for batching TLB flushes Will Deacon
2019-07-24 7:19 ` Joerg Roedel
2019-07-24 7:41 ` Will Deacon
2019-07-25 7:58 ` Joerg Roedel
2019-07-11 17:19 ` [RFC PATCH v2 05/19] iommu: Introduce iommu_iotlb_gather_add_page() Will Deacon
2019-07-11 17:19 ` [RFC PATCH v2 06/19] iommu: Pass struct iommu_iotlb_gather to ->unmap() and ->iotlb_sync() Will Deacon
2019-07-11 17:19 ` [RFC PATCH v2 07/19] iommu/io-pgtable: Introduce tlb_flush_walk() and tlb_flush_leaf() Will Deacon
2019-07-11 17:19 ` [RFC PATCH v2 08/19] iommu/io-pgtable: Hook up ->tlb_flush_walk() and ->tlb_flush_leaf() in drivers Will Deacon
2019-07-11 17:19 ` [RFC PATCH v2 09/19] iommu/io-pgtable-arm: Call ->tlb_flush_walk() and ->tlb_flush_leaf() Will Deacon
2019-07-11 17:19 ` [RFC PATCH v2 10/19] iommu/io-pgtable: Replace ->tlb_add_flush() with ->tlb_add_page() Will Deacon
2019-07-11 17:19 ` [RFC PATCH v2 11/19] iommu/io-pgtable: Remove unused ->tlb_sync() callback Will Deacon
2019-07-11 17:19 ` [RFC PATCH v2 12/19] iommu/io-pgtable: Pass struct iommu_iotlb_gather to ->unmap() Will Deacon
2019-07-11 17:19 ` [RFC PATCH v2 13/19] iommu/io-pgtable: Pass struct iommu_iotlb_gather to ->tlb_add_page() Will Deacon
2019-07-11 17:19 ` [RFC PATCH v2 14/19] iommu/arm-smmu-v3: Separate s/w and h/w views of prod and cons indexes Will Deacon
2019-07-11 17:19 ` [RFC PATCH v2 15/19] iommu/arm-smmu-v3: Drop unused 'q' argument from Q_OVF macro Will Deacon
2019-07-11 17:19 ` [RFC PATCH v2 16/19] iommu/arm-smmu-v3: Move low-level queue fields out of arm_smmu_queue Will Deacon
2019-07-11 17:19 ` [RFC PATCH v2 17/19] iommu/arm-smmu-v3: Operate directly on low-level queue where possible Will Deacon
2019-07-11 17:19 ` [RFC PATCH v2 18/19] iommu/arm-smmu-v3: Reduce contention during command-queue insertion Will Deacon
2019-07-19 11:04 ` John Garry
2019-07-24 12:15 ` Will Deacon
2019-07-24 14:03 ` John Garry
2019-07-24 14:07 ` Will Deacon
2019-07-24 8:20 ` John Garry
2019-07-24 14:33 ` Will Deacon
2019-07-25 11:31 ` John Garry
2019-07-11 17:19 ` [RFC PATCH v2 19/19] iommu/arm-smmu-v3: Defer TLB invalidation until ->iotlb_sync() Will Deacon
2019-07-19 4:25 ` [RFC PATCH v2 00/19] Try to reduce lock contention on the SMMUv3 command queue Ganapatrao Kulkarni
2019-07-24 12:28 ` Will Deacon
2019-07-24 9:58 ` John Garry
2019-07-24 12:20 ` Will Deacon
2019-07-24 14:25 ` John Garry
2019-07-24 14:48 ` Will Deacon
2019-07-25 10:11 ` John Garry
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