On 2023/8/3 8:07, Jason Gunthorpe wrote:
This is used when the iommu driver is taking control of the dma_ops,
currently only on S390 and power spapr. It is designed to preserve the
original ops->detach_dev() semantic that these S390 was built around.
Provide an opaque domain type and a 'default_domain' ops value that allows
the driver to trivially force any single domain as the default domain.
Reviewed-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
---
drivers/iommu/iommu.c | 14 +++++++++++++-
include/linux/iommu.h | 6 ++++++
2 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 5e3cdc9f3a9e78..c64365169b678d 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1705,6 +1705,17 @@ iommu_group_alloc_default_domain(struct iommu_group *group, int req_type)
lockdep_assert_held(&group->mutex);
+ /*
+ * Allow legacy drivers to specify the domain that will be the default
+ * domain. This should always be either an IDENTITY or PLATFORM domain.
+ * Do not use in new drivers.
+ */
+ if (bus->iommu_ops->default_domain) {
+ if (req_type)
+ return ERR_PTR(-EINVAL);
+ return bus->iommu_ops->default_domain;
+ }
+
if (req_type)
return __iommu_group_alloc_default_domain(bus, group, req_type);
@@ -1967,7 +1978,8 @@ void iommu_domain_free(struct iommu_domain *domain)
if (domain->type == IOMMU_DOMAIN_SVA)
mmdrop(domain->mm);
iommu_put_dma_cookie(domain);
- domain->ops->free(domain);
+ if (domain->ops->free)
+ domain->ops->free(domain);
}
EXPORT_SYMBOL_GPL(iommu_domain_free);
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index e05c93b6c37fba..87aebba474e093 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -64,6 +64,7 @@ struct iommu_domain_geometry {
#define __IOMMU_DOMAIN_DMA_FQ (1U << 3) /* DMA-API uses flush queue */
#define __IOMMU_DOMAIN_SVA (1U << 4) /* Shared process address space */
+#define __IOMMU_DOMAIN_PLATFORM (1U << 5)
#define IOMMU_DOMAIN_ALLOC_FLAGS ~__IOMMU_DOMAIN_DMA_FQ
/*
@@ -81,6 +82,8 @@ struct iommu_domain_geometry {
* invalidation.
* IOMMU_DOMAIN_SVA - DMA addresses are shared process addresses
* represented by mm_struct's.
+ * IOMMU_DOMAIN_PLATFORM - Legacy domain for drivers that do their own
+ * dma_api stuff. Do not use in new drivers.
*/
#define IOMMU_DOMAIN_BLOCKED (0U)
#define IOMMU_DOMAIN_IDENTITY (__IOMMU_DOMAIN_PT)
@@ -91,6 +94,7 @@ struct iommu_domain_geometry {
__IOMMU_DOMAIN_DMA_API | \
__IOMMU_DOMAIN_DMA_FQ)
#define IOMMU_DOMAIN_SVA (__IOMMU_DOMAIN_SVA)
+#define IOMMU_DOMAIN_PLATFORM (__IOMMU_DOMAIN_PLATFORM)
struct iommu_domain {
unsigned type;
@@ -256,6 +260,7 @@ struct iommu_iotlb_gather {
* @owner: Driver module providing these ops
* @identity_domain: An always available, always attachable identity
* translation.
+ * @default_domain: If not NULL this will always be set as the default domain.
*/
struct iommu_ops {
bool (*capable)(struct device *dev, enum iommu_cap);
@@ -290,6 +295,7 @@ struct iommu_ops {
unsigned long pgsize_bitmap;
struct module *owner;
struct iommu_domain *identity_domain;
+ struct iommu_domain *default_domain;
I am imaging whether we can merge above two pointers into a single one.
It is either an IDENTITY or PLATFORM domain and the core will choose it
as the default domain of a group if iommu_group_alloc_default_domain()
fails to allocate one through the iommu dev_ops.
Those iommu drivers that could result in a NULL default domain could
provide such domain and guarantee that this domain is always usable for
devices.
Probably we could give it a more meaningful name? For example,
supplemental_domain or rescue_domain?
I am not sure whether this can address the NULL-default-domain issues
of all drivers this series tries to address. So just for discussion
purpose.
Best regards,
baolu
