Re: [PATCH 1/1] Revert "iommu/arm-smmu-v3: Set TTL invalidation hint better"

On 2023/8/1 16:55, Will Deacon wrote:

On Mon, Jul 31, 2023 at 02:21:22PM +0800, wangwudi wrote:

quoted

From: Rui Zhu <redacted>

This reverts commit 6833b8f2e19945a41e4d5efd8c6d9f4cae9a5b7d.

This constraint violates the protocol. When tg is not 0 but ttl, scale,
and num are 0, the hardware reports the CERROR_IL gerror. In the
protocol, leaf is not a prerequisite for TTL.

Cc: Will Deacon <will@kernel.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Yicong Yang <yangyicong@hisilicon.com>
Cc: Tomas Krcka <redacted>
Cc: Jean-Philippe Brucker <redacted>
Cc: Nicolin Chen <redacted>
Cc: Rui Zhu <redacted>

Signed-off-by: Rui Zhu <redacted>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 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 9b0dc3505601..098e84cfa82f 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c

@@ -1898,13 +1898,8 @@ static void __arm_smmu_tlb_inv_range(struct arm_smmu_cmdq_ent *cmd,
 		/* 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.
-		 */
-		if (cmd->tlbi.leaf)
-			cmd->tlbi.ttl = 4 - ((ilog2(granule) - 3) / (tg - 3));
+		/* Determine what level the granule is at */
+		cmd->tlbi.ttl = 4 - ((ilog2(granule) - 3) / (tg - 3));

Doesn't this reintroduce the bug that 6833b8f2e199 tried to fix?

afaict, we should only hit the problematic case of tg != 0 but ttl, scale
and num all 0 if we're invalidating a single page, so shouldn't we just
zap tg in that case, since it's not doing anything useful?

You're right. I'm sorry I missed. I just need to handle the problematic
case by assigning 0 to tg. It's better to add this following code before
each tlbi cmd batch add.

if (num_pages == 1) {
	cmd->tlbi.tg = 0;
}

I'll resubmit a new patch. Thanks for your correction.

I hesitate to say we should avoid range invalidation altogether for
single-page invalidations because I think some errata workarounds might
need that to work.

Will
.

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