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

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Message-ID: <Z3yvZsq77bpnaoAb@Asurada-Nvidia>
Date: Mon, 6 Jan 2025 20:36:54 -0800
From: Nicolin Chen <nicolinc@...dia.com>
To: Baolu Lu <baolu.lu@...ux.intel.com>
CC: <jgg@...dia.com>, <kevin.tian@...el.com>, <corbet@....net>,
	<will@...nel.org>, <joro@...tes.org>, <suravee.suthikulpanit@....com>,
	<robin.murphy@....com>, <dwmw2@...radead.org>, <shuah@...nel.org>,
	<linux-kernel@...r.kernel.org>, <iommu@...ts.linux.dev>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kselftest@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <eric.auger@...hat.com>,
	<jean-philippe@...aro.org>, <mdf@...nel.org>, <mshavit@...gle.com>,
	<shameerali.kolothum.thodi@...wei.com>, <smostafa@...gle.com>,
	<ddutile@...hat.com>, <yi.l.liu@...el.com>, <patches@...ts.linux.dev>
Subject: Re: [PATCH v4 14/14] iommu/arm-smmu-v3: Report events that belong to
 devices attached to vIOMMU

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;
+}
+
 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,
 };
 
 struct iommufd_viommu *arm_vsmmu_alloc(struct device *dev,
diff --git a/drivers/iommu/iommufd/eventq.c b/drivers/iommu/iommufd/eventq.c
index bf0c04f571a7..b5be629f38ed 100644
--- a/drivers/iommu/iommufd/eventq.c
+++ b/drivers/iommu/iommufd/eventq.c
@@ -555,6 +555,11 @@ int iommufd_veventq_alloc(struct iommufd_ucmd *ucmd)
 	viommu = iommufd_get_viommu(ucmd, cmd->viommu_id);
 	if (IS_ERR(viommu))
 		return PTR_ERR(viommu);
+
+	if (!viommu->ops || !viommu->ops->supports_veventq ||
+	    !viommu->ops->supports_veventq(cmd->type))
+		return -EOPNOTSUPP;
+
 	down_write(&viommu->veventqs_rwsem);
 
 	if (iommufd_viommu_find_veventq(viommu, cmd->type)) {
diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
index 6b3b46e382f8..55e71dca3664 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -117,6 +117,7 @@ struct iommufd_viommu {
  *                    array->entry_num to report the number of handled requests.
  *                    The data structure of the array entry must be defined in
  *                    include/uapi/linux/iommufd.h
+ * @supports_veventq: Whether the vIOMMU supports a given vEVENTQ type
  */
 struct iommufd_viommu_ops {
 	void (*destroy)(struct iommufd_viommu *viommu);
@@ -125,6 +126,7 @@ struct iommufd_viommu_ops {
 		const struct iommu_user_data *user_data);
 	int (*cache_invalidate)(struct iommufd_viommu *viommu,
 				struct iommu_user_data_array *array);
+	bool (*supports_veventq)(unsigned int type);
 };
 
 #if IS_ENABLED(CONFIG_IOMMUFD)