diff mbox series

[v4,7/8] iommu/arm-smmu-v3: Skip cd sync if CD table isn't active

Message ID 20230803003234.v4.7.Idedc0f496231e2faab3df057219c5e2d937bbfe4@changeid (mailing list archive)
State New, archived
Headers show
Series Refactor the SMMU's CD table ownership | expand

Commit Message

Michael Shavit Aug. 2, 2023, 4:32 p.m. UTC 
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.

Signed-off-by: Michael Shavit <mshavit@google.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
---

(no changes since v3)

Changes in v3:
- Flip the cd_table.installed bit back off when table is detached
- re-order the commit later in the series since flipping the installed
  bit to off isn't obvious when the cd_table is still shared by multiple
  masters.

Changes in v2:
- Store field as a bit instead of a bool. Fix comment about STE being
  live before the sync in write_ctx_desc().

 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 8 +++++++-
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 2 ++
 2 files changed, 9 insertions(+), 1 deletion(-)

Comments

Nicolin Chen Aug. 4, 2023, 7:59 p.m. UTC | #1 
On Thu, Aug 03, 2023 at 12:32:35AM +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.

> @@ -1360,6 +1363,9 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_master *master, u32 sid,
>                                   cd_table->l1_desc ?
>                                           STRTAB_STE_0_S1FMT_64K_L2 :
>                                           STRTAB_STE_0_S1FMT_LINEAR);
> +               cd_table->installed = true;
> +       } else {
> +               master->cd_table.installed = false;

Before this chunk, there is another fork for "Bypass/fault", where
we could set "installed" to false too, although it doesn't seem to
cause a problem at this moment since arm_smmu_sync_cd() is called
only in the context of an ARM_SMMU_DOMAIN_S1.

Otherwise,

Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Michael Shavit Aug. 7, 2023, 3:02 p.m. UTC | #2 
On Sat, Aug 5, 2023 at 3:59 AM Nicolin Chen <nicolinc@nvidia.com> wrote:
>
> Before this chunk, there is another fork for "Bypass/fault", where
> we could set "installed" to false too, although it doesn't seem to
> cause a problem at this moment since arm_smmu_sync_cd() is called
> only in the context of an ARM_SMMU_DOMAIN_S1.

Oh, good catch; I didn't notice the return in that branch.
Fixing in v5.
diff mbox series

Patch

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 e2c33024ad85..00b602ae9636 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;
+
 	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.
 		 */
@@ -1360,6 +1363,9 @@  static void arm_smmu_write_strtab_ent(struct arm_smmu_master *master, u32 sid,
 				  cd_table->l1_desc ?
 					  STRTAB_STE_0_S1FMT_64K_L2 :
 					  STRTAB_STE_0_S1FMT_LINEAR);
+		cd_table->installed = true;
+	} else {
+		master->cd_table.installed = false;
 	}
 
 	if (s2_cfg) {
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
index 1f3b37025777..e76452e735a0 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -599,6 +599,8 @@  struct arm_smmu_ctx_desc_cfg {
 	u8				max_cds_bits;
 	/* Whether CD entries in this table have the stall bit set. */
 	u8				stall_enabled:1;
+	/* Whether this CD table is installed in any STE */
+	u8				installed:1;
 };
 
 struct arm_smmu_s2_cfg {