[PATCH] iommu/arm-smmu-v3: Avoid constructing invalid range commands

[PATCH] iommu/arm-smmu-v3: Avoid constructing invalid range commands

[Robin Murphy]

Although io-pgtable's non-leaf invalidations are always for full tables,
I missed that SVA also uses non-leaf invalidations, while being at the
mercy of whatever range the MMU notifier throws at it. This means it
definitely wants the previous TTL fix as well, since it also doesn't
know exactly which leaf level(s) may need invalidating, but it can also
give us less-aligned ranges wherein certain corners may lead to building
an invalid command where TTL, Num and Scale are all 0. It should be fine
to handle this by over-invalidating an extra page, since falling back to
a non-range command opens up a whole can of errata-flavoured worms.

Fixes: 6833b8f2e199 ("iommu/arm-smmu-v3: Set TTL invalidation hint better")
Reported-by: Rui Zhu <zhurui3@huawei.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---

Proper resend of previous inline patch[1], now based on 6.6-rc1.

[1] https://lore.kernel.org/linux-iommu/280d0be7-7d41-ed78-bf4b-3db6c0076e22@arm.com/

 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index e82bf1c449a3..bd0a596f9863 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -1895,18 +1895,23 @@ static void __arm_smmu_tlb_inv_range(struct arm_smmu_cmdq_ent *cmd,
 		/* Get the leaf page size */
 		tg = __ffs(smmu_domain->domain.pgsize_bitmap);
 
+		num_pages = size >> tg;
+
 		/* Convert page size of 12,14,16 (log2) to 1,2,3 */
 		cmd->tlbi.tg = (tg - 10) / 2;
 
 		/*
-		 * Determine what level the granule is at. For non-leaf, io-pgtable
-		 * assumes .tlb_flush_walk can invalidate multiple levels at once,
-		 * so ignore the nominal last-level granule and leave TTL=0.
+		 * Determine what level the granule is at. For non-leaf, both
+		 * io-pgtable and SVA pass a nominal last-level granule because
+		 * they don't know what level(s) actually apply, so ignore that
+		 * and leave TTL=0. However for various errata reasons we still
+		 * want to use a range command, so avoid the SVA corner case
+		 * where both scale and num could be 0 as well.
 		 */
 		if (cmd->tlbi.leaf)
 			cmd->tlbi.ttl = 4 - ((ilog2(granule) - 3) / (tg - 3));
-
-		num_pages = size >> tg;
+		else if ((num_pages & CMDQ_TLBI_RANGE_NUM_MAX) == 1)
+			num_pages++;
 	}
 
 	cmds.num = 0;
-- 
2.39.2.101.g768bb238c484.dirty


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Re: [PATCH] iommu/arm-smmu-v3: Avoid constructing invalid range commands

[Will Deacon]

On Mon, 11 Sep 2023 12:57:04 +0100, Robin Murphy wrote:
> Although io-pgtable's non-leaf invalidations are always for full tables,
> I missed that SVA also uses non-leaf invalidations, while being at the
> mercy of whatever range the MMU notifier throws at it. This means it
> definitely wants the previous TTL fix as well, since it also doesn't
> know exactly which leaf level(s) may need invalidating, but it can also
> give us less-aligned ranges wherein certain corners may lead to building
> an invalid command where TTL, Num and Scale are all 0. It should be fine
> to handle this by over-invalidating an extra page, since falling back to
> a non-range command opens up a whole can of errata-flavoured worms.
> 
> [...]

Applied to will (for-joerg/arm-smmu/fixes), thanks!

[1/1] iommu/arm-smmu-v3: Avoid constructing invalid range commands
      https://git.kernel.org/will/c/eb6c97647be2

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev

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