diff mbox series

[v4,18/23] iommu/arm-smmu-v3-iommufd: Support implementation-defined hw_info

Message ID f70cdcc21df7cf07ae1da02aba8a5aa932718a25.1746757630.git.nicolinc@nvidia.com
State New
Headers show
Series iommufd: Add vIOMMU infrastructure (Part-4 HW QUEUE) | expand

Commit Message

Nicolin Chen May 9, 2025, 3:02 a.m. UTC 
Repurpose the @__reserved field in the struct iommu_hw_info_arm_smmuv3,
to an HW implementation-defined field @impl.

This will be used by Tegra241 CMDQV implementation on top of a standard
ARM SMMUv3 IOMMU. The @impl will be only valid if @flags is set with an
implementation-defined flag.

Thus in the driver-level, add an hw_info impl op that will return such
a flag and fill the impl field.

Reviewed-by: Pranjal Shrivastava <praan@google.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h     |  1 +
 include/uapi/linux/iommufd.h                    |  4 ++--
 .../iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c | 17 ++++++++++++++---
 3 files changed, 17 insertions(+), 5 deletions(-)

Comments

Jason Gunthorpe May 15, 2025, 5:17 p.m. UTC | #1 
On Thu, May 08, 2025 at 08:02:39PM -0700, Nicolin Chen wrote:
> Repurpose the @__reserved field in the struct iommu_hw_info_arm_smmuv3,
> to an HW implementation-defined field @impl.

It would be nicer to have a tegra/cmdq specific struct and a way for
iommu_hw_info to select it. 'impl' isn't going to scale very well if
something else wants to use this.

We have out_data_type but we could have an input sub_data_type too. 0
means what we have today, then a simple enum to select another info
struct.

> @@ -726,6 +726,7 @@ struct arm_smmu_impl_ops {
>  		struct arm_smmu_domain *smmu_domain, struct iommufd_ctx *ictx,
>  		unsigned int viommu_type,
>  		const struct iommu_user_data *user_data);
> +	u32 (*hw_info)(struct arm_smmu_device *smmu, u32 *impl);
>  };

Then the dispatch here is just having a sub-struct enum # in
arm_smmu_impl_ops for dispatching.

Jason
Nicolin Chen May 15, 2025, 6:52 p.m. UTC | #2 
On Thu, May 15, 2025 at 02:17:06PM -0300, Jason Gunthorpe wrote:
> On Thu, May 08, 2025 at 08:02:39PM -0700, Nicolin Chen wrote:
> > Repurpose the @__reserved field in the struct iommu_hw_info_arm_smmuv3,
> > to an HW implementation-defined field @impl.
> 
> It would be nicer to have a tegra/cmdq specific struct and a way for
> iommu_hw_info to select it. 'impl' isn't going to scale very well if
> something else wants to use this.
> 
> We have out_data_type but we could have an input sub_data_type too. 0
> means what we have today, then a simple enum to select another info
> struct.

So, there will be two hw_info calls back to back right?

Should the first call return out_data_type=CMDQV while returning
the arm_smmu_v3 hw_info data? Otherwise, VMM wouldn't know what
to set in the input sub_data_type of the 2nd ioctl?

Thanks
Nicolin
Jason Gunthorpe May 15, 2025, 6:56 p.m. UTC | #3 
On Thu, May 15, 2025 at 11:52:05AM -0700, Nicolin Chen wrote:
> On Thu, May 15, 2025 at 02:17:06PM -0300, Jason Gunthorpe wrote:
> > On Thu, May 08, 2025 at 08:02:39PM -0700, Nicolin Chen wrote:
> > > Repurpose the @__reserved field in the struct iommu_hw_info_arm_smmuv3,
> > > to an HW implementation-defined field @impl.
> > 
> > It would be nicer to have a tegra/cmdq specific struct and a way for
> > iommu_hw_info to select it. 'impl' isn't going to scale very well if
> > something else wants to use this.
> > 
> > We have out_data_type but we could have an input sub_data_type too. 0
> > means what we have today, then a simple enum to select another info
> > struct.
> 
> So, there will be two hw_info calls back to back right?

yes

> Should the first call return out_data_type=CMDQV while returning
> the arm_smmu_v3 hw_info data? Otherwise, VMM wouldn't know what
> to set in the input sub_data_type of the 2nd ioctl?

No, either set a flag in the smmu_v3 hw_info, as you were doing here,
or just have the vmm probe it. Given the VMM is likely to be told to
run in vCMDQ mode on the command line try-and-fail doesn't sound so
bad.

And I guess we don't need a "sub type" just a "requested type" where 0
means return the best one and non-zero means return a specific one or
fail with EOPNOTSUPP.

Jason
Nicolin Chen May 15, 2025, 8:17 p.m. UTC | #4 
On Thu, May 15, 2025 at 04:23:29PM -0300, Jason Gunthorpe wrote:
> On Thu, May 15, 2025 at 12:21:17PM -0700, Nicolin Chen wrote:
> > On Thu, May 15, 2025 at 03:56:29PM -0300, Jason Gunthorpe wrote:
> > > On Thu, May 15, 2025 at 11:52:05AM -0700, Nicolin Chen wrote:
> > > > On Thu, May 15, 2025 at 02:17:06PM -0300, Jason Gunthorpe wrote:
> > > > > On Thu, May 08, 2025 at 08:02:39PM -0700, Nicolin Chen wrote:
> > > > Should the first call return out_data_type=CMDQV while returning
> > > > the arm_smmu_v3 hw_info data? Otherwise, VMM wouldn't know what
> > > > to set in the input sub_data_type of the 2nd ioctl?
> > > 
> > > No, either set a flag in the smmu_v3 hw_info, as you were doing here,
> > > or just have the vmm probe it. Given the VMM is likely to be told to
> > > run in vCMDQ mode on the command line try-and-fail doesn't sound so
> > > bad.
> > > 
> > > And I guess we don't need a "sub type" just a "requested type" where 0
> > > means return the best one and non-zero means return a specific one or
> > > fail with EOPNOTSUPP.
> > 
> > OK. I think this would work:
> > hw_info (req_type=0)     => out_data_type=SMMU_V3, flags=HAS_CMDQV
> > hw_info (req_type=CMDQV) => out_data_type=CMDQV,   flags=0
> 
> Yeah
> 
> > Or, would it be simpler by having a sub_data_uptr:
> > hw_info => out_data_type=SMMU_V3, sub_data_type=CMDQV,
> >            data_uptr=iommu_hw_info_arm_smmuv3,
> > 	   sub_data_uptr=iommu_hw_info_tegra241_cmdqv
> > ?
> 
> I think the former is simpler to code, you can just add the req_type
> to the signatures and if the driver comes back with a type != req_type
> the core code will return EOPNOTSUPP

OK.

Maybe just turn the out_data_type to be bidirectional?

Then we would only need to update the docs:
 /**
  * enum iommu_hw_info_type - IOMMU Hardware Info Types
- * @IOMMU_HW_INFO_TYPE_NONE: Used by the drivers that do not report hardware
- *                           info
+ * @IOMMU_HW_INFO_TYPE_NONE: (for output) used by the drivers that do not report
+ *                           hardware info
+ * @IOMMU_HW_INFO_TYPE_DEFAULT: (for input) Used to request the default type
  * @IOMMU_HW_INFO_TYPE_INTEL_VTD: Intel VT-d iommu info type
  * @IOMMU_HW_INFO_TYPE_ARM_SMMUV3: ARM SMMUv3 iommu info type
+ * @IOMMU_HW_INFO_TYPE_TEGRA241_CMDQV: Subtype of ARM SMMUv3 for Tegra241 CMDQV
  */
 enum iommu_hw_info_type {
 	IOMMU_HW_INFO_TYPE_NONE = 0,
+ 	IOMMU_HW_INFO_TYPE_DEFAULT = 0,
 	IOMMU_HW_INFO_TYPE_INTEL_VTD = 1,
 	IOMMU_HW_INFO_TYPE_ARM_SMMUV3 = 2,
+	IOMMU_HW_INFO_TYPE_TEGRA241_CMDQV =3,
 };

- * @out_data_type: Output the iommu hardware info type as defined in the enum
- *                 iommu_hw_info_type.
+ * @data_type: Bidirectional property.
+ *             Input the requested iommu hardware info type as defined in the
+ *             enum iommu_hw_info_type. Requesting IOMMU_HW_INFO_TYPE_DEFAULT
+ *             lets kernel pick the default type to output, otherwise kernel
+ *             will validate the input type and may reject with -EOPNOTSUPP.
+ *             Output the supported iommu hardware info type as defined in the
+ *             same enum iommu_hw_info_type

And similarly in the iommu API kdoc too.

> Finally we end up with only one ioctl enum number space for the
> types, which seems appealing.

Yea. Avoiding a sub enum is nicer.

Thanks
Nicolin
diff mbox series

Patch

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 a5835af72417..bab7a9ce1283 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -726,6 +726,7 @@  struct arm_smmu_impl_ops {
 		struct arm_smmu_domain *smmu_domain, struct iommufd_ctx *ictx,
 		unsigned int viommu_type,
 		const struct iommu_user_data *user_data);
+	u32 (*hw_info)(struct arm_smmu_device *smmu, u32 *impl);
 };
 
 /* An SMMUv3 instance */
diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
index 001e2deb5a2d..28ab42a85268 100644
--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -554,7 +554,7 @@  struct iommu_hw_info_vtd {
  *                                   (IOMMU_HW_INFO_TYPE_ARM_SMMUV3)
  *
  * @flags: Must be set to 0
- * @__reserved: Must be 0
+ * @impl: Must be 0
  * @idr: Implemented features for ARM SMMU Non-secure programming interface
  * @iidr: Information about the implementation and implementer of ARM SMMU,
  *        and architecture version supported
@@ -585,7 +585,7 @@  struct iommu_hw_info_vtd {
  */
 struct iommu_hw_info_arm_smmuv3 {
 	__u32 flags;
-	__u32 __reserved;
+	__u32 impl;
 	__u32 idr[6];
 	__u32 iidr;
 	__u32 aidr;
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 b316d1df043f..8ea9a022e444 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
@@ -10,6 +10,7 @@ 
 void *arm_smmu_hw_info(struct device *dev, u32 *length, u32 *type)
 {
 	struct arm_smmu_master *master = dev_iommu_priv_get(dev);
+	struct arm_smmu_device *smmu = master->smmu;
 	struct iommu_hw_info_arm_smmuv3 *info;
 	u32 __iomem *base_idr;
 	unsigned int i;
@@ -18,15 +19,25 @@  void *arm_smmu_hw_info(struct device *dev, u32 *length, u32 *type)
 	if (!info)
 		return ERR_PTR(-ENOMEM);
 
-	base_idr = master->smmu->base + ARM_SMMU_IDR0;
+	base_idr = smmu->base + ARM_SMMU_IDR0;
 	for (i = 0; i <= 5; i++)
 		info->idr[i] = readl_relaxed(base_idr + i);
-	info->iidr = readl_relaxed(master->smmu->base + ARM_SMMU_IIDR);
-	info->aidr = readl_relaxed(master->smmu->base + ARM_SMMU_AIDR);
+	info->iidr = readl_relaxed(smmu->base + ARM_SMMU_IIDR);
+	info->aidr = readl_relaxed(smmu->base + ARM_SMMU_AIDR);
 
 	*length = sizeof(*info);
 	*type = IOMMU_HW_INFO_TYPE_ARM_SMMUV3;
 
+	if (smmu->impl_ops && smmu->impl_ops->hw_info) {
+		u32 flags, impl;
+
+		flags = smmu->impl_ops->hw_info(smmu, &impl);
+		if (flags) {
+			info->impl = impl;
+			info->flags |= flags;
+		}
+	}
+
 	return info;
 }