From: Will Deacon <will@kernel.org>
To: Michael Shavit <mshavit@google.com>
Cc: iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, robin.murphy@arm.com,
nicolinc@nvidia.com, jgg@nvidia.com, jean-philippe@linaro.org
Subject: Re: [PATCH v5 8/9] iommu/arm-smmu-v3: Skip cd sync if CD table isn't active
Date: Wed, 9 Aug 2023 14:50:13 +0100 [thread overview]
Message-ID: <20230809135011.GC4226@willie-the-truck> (raw)
In-Reply-To: <20230809011204.v5.8.Idedc0f496231e2faab3df057219c5e2d937bbfe4@changeid>
On Wed, Aug 09, 2023 at 01:12:04AM +0800, Michael Shavit wrote:
> This commit explicitly keeps track of whether a CD table is installed in
> an STE so that arm_smmu_sync_cd can skip the sync when unnecessary. This
> was previously achieved through the domain->devices list, but we are
> moving to a model where arm_smmu_sync_cd directly operates on a master
> and the master's CD table instead of a domain.
Why is this path worth optimising?
> 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 f5ad386cc8760..488d12dd2d4aa 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -985,6 +985,9 @@ static void arm_smmu_sync_cd(struct arm_smmu_master *master,
> },
> };
>
> + if (!master->cd_table.installed)
> + return;
Doesn't this interact badly with the sync in arm_smmu_detach_dev(), which I
think happens after zapping the STE?
> cmds.num = 0;
> for (i = 0; i < master->num_streams; i++) {
> cmd.cfgi.sid = master->streams[i].id;
> @@ -1091,7 +1094,7 @@ int arm_smmu_write_ctx_desc(struct arm_smmu_master *master, int ssid,
> cdptr[3] = cpu_to_le64(cd->mair);
>
> /*
> - * STE is live, and the SMMU might read dwords of this CD in any
> + * STE may be live, and the SMMU might read dwords of this CD in any
> * order. Ensure that it observes valid values before reading
> * V=1.
> */
Why does this patch need to update this comment?
Will
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next prev parent reply other threads:[~2023-08-09 13:50 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-08 17:11 [PATCH v5 0/9] Refactor the SMMU's CD table ownership Michael Shavit
2023-08-08 17:11 ` [PATCH v5 1/9] iommu/arm-smmu-v3: Move ctx_desc out of s1_cfg Michael Shavit
2023-08-08 17:11 ` [PATCH v5 2/9] iommu/arm-smmu-v3: Replace s1_cfg with cdtab_cfg Michael Shavit
2023-08-09 13:49 ` Will Deacon
2023-08-09 13:59 ` Jason Gunthorpe
2023-08-09 14:55 ` Will Deacon
2023-08-09 15:08 ` Jason Gunthorpe
2023-08-09 16:22 ` Will Deacon
2023-08-09 16:26 ` Jason Gunthorpe
2023-08-09 16:27 ` Will Deacon
2023-08-10 9:33 ` Michael Shavit
2023-08-10 9:43 ` Will Deacon
2023-08-10 12:04 ` Jason Gunthorpe
2023-08-10 17:15 ` Michael Shavit
2023-08-10 17:32 ` Jason Gunthorpe
2023-08-08 17:11 ` [PATCH v5 3/9] iommu/arm-smmu-v3: Encapsulate ctx_desc_cfg init in alloc_cd_tables Michael Shavit
2023-08-08 17:12 ` [PATCH v5 4/9] iommu/arm-smmu-v3: move stall_enabled to the cd table Michael Shavit
2023-08-08 17:12 ` [PATCH v5 5/9] iommu/arm-smmu-v3: Refactor write_ctx_desc Michael Shavit
2023-08-09 13:50 ` Will Deacon
2023-08-10 9:15 ` Michael Shavit
2023-08-10 14:40 ` Will Deacon
2023-08-10 15:39 ` Jason Gunthorpe
2023-08-15 5:20 ` Michael Shavit
2023-08-15 11:22 ` Jason Gunthorpe
2023-08-15 12:03 ` Michael Shavit
2023-08-15 12:30 ` Jason Gunthorpe
2023-08-15 12:36 ` Michael Shavit
2023-08-15 12:56 ` Jason Gunthorpe
2023-08-15 5:04 ` Michael Shavit
2023-08-15 10:19 ` Will Deacon
2023-08-15 11:40 ` Michael Shavit
2023-08-08 17:12 ` [PATCH v5 6/9] iommu/arm-smmu-v3: Move CD table to arm_smmu_master Michael Shavit
2023-08-09 13:50 ` Will Deacon
2023-08-10 9:23 ` Michael Shavit
2023-08-10 14:38 ` Will Deacon
2023-08-10 9:45 ` Michael Shavit
2023-08-10 14:34 ` Will Deacon
2023-08-10 14:56 ` Jason Gunthorpe
2023-08-15 12:10 ` Michael Shavit
2023-08-08 17:12 ` [PATCH v5 7/9] iommu/arm-smmu-v3: Cleanup arm_smmu_domain_finalise Michael Shavit
2023-08-08 17:12 ` [PATCH v5 8/9] iommu/arm-smmu-v3: Skip cd sync if CD table isn't active Michael Shavit
2023-08-09 13:50 ` Will Deacon [this message]
2023-08-10 8:34 ` Michael Shavit
2023-08-10 16:27 ` Will Deacon
2023-08-08 17:12 ` [PATCH v5 9/9] iommu/arm-smmu-v3: Rename cdcfg to cd_table Michael Shavit
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