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    Subject[PATCH v4 7/8] iommu/arm-smmu-v3: Skip cd sync if CD table isn't active
    From
    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(-)

    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 {
    --
    2.41.0.585.gd2178a4bd4-goog
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