[PATCH v3 23/25] iommu: Add ops->domain_alloc_paging()
Baolu Lu
baolu.lu at linux.intel.com
Sat Jun 10 02:08:31 PDT 2023
On 6/10/23 3:56 AM, Jason Gunthorpe wrote:
> This callback requests the driver to create only a __IOMMU_DOMAIN_PAGING
> domain, so it saves a few lines in a lot of drivers needlessly checking
> the type.
>
> More critically, this allows us to sweep out all the
> IOMMU_DOMAIN_UNMANAGED and IOMMU_DOMAIN_DMA checks from a lot of the
> drivers, simplifying what is going on in the code and ultimately removing
> the now-unused special cases in drivers where they did not support
> IOMMU_DOMAIN_DMA.
>
> domain_alloc_paging() should return a struct iommu_domain that is
> functionally compatible with ARM_DMA_USE_IOMMU, dma-iommu.c and iommufd.
>
> Be forwards looking and pass in a 'struct device *' argument. We can
> provide this when allocating the default_domain. No drivers will look at
> this.
I like this idea. :-)
>
> Tested-by: Steven Price <steven.price at arm.com>
> Tested-by: Marek Szyprowski <m.szyprowski at samsung.com>
> Tested-by: Nicolin Chen <nicolinc at nvidia.com>
> Signed-off-by: Jason Gunthorpe <jgg at nvidia.com>
> ---
> drivers/iommu/iommu.c | 13 ++++++++++---
> include/linux/iommu.h | 3 +++
> 2 files changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 0346c05e108438..2cf523ff9c6f55 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1985,6 +1985,7 @@ void iommu_set_fault_handler(struct iommu_domain *domain,
> EXPORT_SYMBOL_GPL(iommu_set_fault_handler);
>
> static struct iommu_domain *__iommu_domain_alloc(const struct iommu_ops *ops,
> + struct device *dev,
> unsigned int type)
> {
> struct iommu_domain *domain;
> @@ -1992,8 +1993,13 @@ static struct iommu_domain *__iommu_domain_alloc(const struct iommu_ops *ops,
>
> if (alloc_type == IOMMU_DOMAIN_IDENTITY && ops->identity_domain)
> return ops->identity_domain;
> + else if (type & __IOMMU_DOMAIN_PAGING) {
> + domain = ops->domain_alloc_paging(dev);
This might be problematic because not all IOMMU drivers implement this
callback now. In the missing cases, the code will always result in a
null pointer reference issue?
> + } else if (ops->domain_alloc)
> + domain = ops->domain_alloc(alloc_type);
> + else
> + return NULL;
>
> - domain = ops->domain_alloc(alloc_type);
> if (!domain)
> return NULL;
>
> @@ -2024,14 +2030,15 @@ __iommu_group_domain_alloc(struct iommu_group *group, unsigned int type)
>
> lockdep_assert_held(&group->mutex);
>
> - return __iommu_domain_alloc(dev_iommu_ops(dev), type);
> + return __iommu_domain_alloc(dev_iommu_ops(dev), dev, type);
> }
>
> struct iommu_domain *iommu_domain_alloc(const struct bus_type *bus)
> {
> if (bus == NULL || bus->iommu_ops == NULL)
> return NULL;
> - return __iommu_domain_alloc(bus->iommu_ops, IOMMU_DOMAIN_UNMANAGED);
> + return __iommu_domain_alloc(bus->iommu_ops, NULL,
> + IOMMU_DOMAIN_UNMANAGED);
Suppose that iommu_domain_alloc() is always called from device drivers
where device pointer is always available. Is it possible to convert it
to a real device pointer?
> }
> EXPORT_SYMBOL_GPL(iommu_domain_alloc);
>
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 49331573f1d1f5..8e4d178c49c417 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -233,6 +233,8 @@ struct iommu_iotlb_gather {
> * struct iommu_ops - iommu ops and capabilities
> * @capable: check capability
> * @domain_alloc: allocate iommu domain
> + * @domain_alloc_paging: Allocate an iommu_domain that can be used for
> + * UNMANAGED, DMA, and DMA_FQ domain types.
> * @probe_device: Add device to iommu driver handling
> * @release_device: Remove device from iommu driver handling
> * @probe_finalize: Do final setup work after the device is added to an IOMMU
> @@ -264,6 +266,7 @@ struct iommu_ops {
>
> /* Domain allocation and freeing by the iommu driver */
> struct iommu_domain *(*domain_alloc)(unsigned iommu_domain_type);
> + struct iommu_domain *(*domain_alloc_paging)(struct device *dev);
>
> struct iommu_device *(*probe_device)(struct device *dev);
> void (*release_device)(struct device *dev);
Best regards,
baolu
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