On Thu, 21 Jan 2021 13:36:24 +0100
Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx> wrote:
> The SMMU provides a Stall model for handling page faults in platform
> devices. It is similar to PCIe PRI, but doesn't require devices to have
> their own translation cache. Instead, faulting transactions are parked
> and the OS is given a chance to fix the page tables and retry the
> transaction.
>
> Enable stall for devices that support it (opt-in by firmware). When an
> event corresponds to a translation error, call the IOMMU fault handler.
> If the fault is recoverable, it will call us back to terminate or
> continue the stall.
>
> To use stall device drivers need to enable IOMMU_DEV_FEAT_IOPF, which
> initializes the fault queue for the device.
>
> Tested-by: Zhangfei Gao <zhangfei.gao@xxxxxxxxxx>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
One thing inline + one comment which was mostly a case of I ran
out of time to walk through why probe and release aren't symmetric...
> ---
> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 43 ++++
> .../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 59 +++++-
> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 185 +++++++++++++++++-
> 3 files changed, 273 insertions(+), 14 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 db5d6aa76c3a..af6982aca42e 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -32,6 +32,7 @@
...
>
> master->domain = smmu_domain;
> @@ -2484,6 +2624,11 @@ static struct iommu_device *arm_smmu_probe_device(struct device *dev)
> master->ssid_bits = min_t(u8, master->ssid_bits,
> CTXDESC_LINEAR_CDMAX);
>
> + if ((smmu->features & ARM_SMMU_FEAT_STALLS &&
> + device_property_read_bool(dev, "dma-can-stall")) ||
> + smmu->features & ARM_SMMU_FEAT_STALL_FORCE)
> + master->stall_enabled = true;
> +
> return &smmu->iommu;
>
> err_free_master:
> @@ -2502,6 +2647,7 @@ static void arm_smmu_release_device(struct device *dev)
>
> master = dev_iommu_priv_get(dev);
> WARN_ON(arm_smmu_master_sva_enabled(master));
> + iopf_queue_remove_device(master->smmu->evtq.iopf, dev);
> arm_smmu_detach_dev(master);
> arm_smmu_disable_pasid(master);
> arm_smmu_remove_master(master);
The lack of symmetry here bothers me a bit, but it's already true, so I guess
this case is fine as well.
...
>
> @@ -2785,6 +2946,7 @@ static int arm_smmu_cmdq_init(struct arm_smmu_device *smmu)
> static int arm_smmu_init_queues(struct arm_smmu_device *smmu)
> {
> int ret;
> + bool sva = smmu->features & ARM_SMMU_FEAT_STALLS;
FEAT_SVA?
>
> /* cmdq */
> ret = arm_smmu_init_one_queue(smmu, &smmu->cmdq.q, ARM_SMMU_CMDQ_PROD,
> @@ -2804,6 +2966,12 @@ static int arm_smmu_init_queues(struct arm_smmu_device *smmu)
> if (ret)
> return ret;
>
> + if (sva && smmu->features & ARM_SMMU_FEAT_STALLS) {
Isn't this checking same thing twice?
> + smmu->evtq.iopf = iopf_queue_alloc(dev_name(smmu->dev));
> + if (!smmu->evtq.iopf)
> + return -ENOMEM;
> + }
> +
> /* priq */
> if (!(smmu->features & ARM_SMMU_FEAT_PRI))
> return 0;
> @@ -3718,6 +3886,7 @@ static int arm_smmu_device_remove(struct platform_device *pdev)
> iommu_device_unregister(&smmu->iommu);
> iommu_device_sysfs_remove(&smmu->iommu);
> arm_smmu_device_disable(smmu);
> + iopf_queue_free(smmu->evtq.iopf);
>
> return 0;
> }
