Re: [PATCH v4 14/14] iommu/arm-smmu-v3: Report events that belong to devices attached to vIOMMU

[Baolu Lu]

On 1/7/25 12:36, Nicolin Chen wrote:

On Mon, Jan 06, 2025 at 10:46:21AM -0800, Nicolin Chen wrote:

On Mon, Jan 06, 2025 at 11:01:32AM +0800, Baolu Lu wrote:

Nit: I think it would be more readable to add a check in the vevent
reporting helper.

diff --git a/drivers/iommu/iommufd/driver.c b/drivers/iommu/iommufd/driver.c
index 77c34f8791ef..ccada0ada5ff 100644
--- a/drivers/iommu/iommufd/driver.c
+++ b/drivers/iommu/iommufd/driver.c
@@ -86,6 +86,9 @@ int iommufd_viommu_report_event(struct iommufd_viommu
*viommu,
         if (WARN_ON_ONCE(!data_len || !event_data))
                 return -EINVAL;

+       if (WARN_ON_ONCE(type != IOMMU_VEVENTQ_TYPE_ARM_SMMUV3))
+               return -EINVAL;
+

Hmm, that's a good point I think.

         down_read(&viommu->veventqs_rwsem);

         veventq = iommufd_viommu_find_veventq(viommu, type);

                    ^
                    |
We actually have been missing a type validation entirely, so the
type could have been rejected by this function. Perhaps we should
add a static list of supported types to struct iommufd_viommu_ops
for drivers to report so that then the core could reject from the
first place during a vEVENTQ allocation.

I added something like this. Will send a v5.

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c 
b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
index 0c7a5894ba07..348179f3cf2a 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
@@ -399,9 +399,15 @@ static int arm_vsmmu_cache_invalidate(struct 
iommufd_viommu *viommu,
        return ret;
  }

+static bool arm_vsmmu_supports_veventq(unsigned int type)

+{
+       return type == IOMMU_VIOMMU_TYPE_ARM_SMMUV3;

Do you need to check the hardware capabilities before reporting this? I
am not familiar with the ARM architecture, but typically it's better to
make it like this,

static bool arm_vsmmu_supports_veventq(struct iommufd_viommu *viommu,
                                       enum iommu_veventq_type type)
{
        if (type != IOMMU_VEVENTQ_TYPE_ARM_SMMUV3)
                return false;

        if (hardware_not_capable(viommu))
                return false;

        return true;
}

+}
+
  static const struct iommufd_viommu_ops arm_vsmmu_ops = {
        .alloc_domain_nested = arm_vsmmu_alloc_domain_nested,
        .cache_invalidate = arm_vsmmu_cache_invalidate,
+       .supports_veventq = arm_vsmmu_supports_veventq,
  };

Others look good to me.

Thanks,
baolu