[PATCH 1/8] iommu/vt-d: clean up 32bit si_domain assignment

Tom Murphy
2019-12-21T15:04:21Z

In the intel iommu driver devices which only support 32bit DMA can't be
direct mapped. The implementation of this is weird. Currently we assign
it a direct mapped domain and then remove the domain later and replace
it with a domain of type IOMMU_DOMAIN_IDENTITY. We should just assign it
a domain of type IOMMU_DOMAIN_IDENTITY from the begging rather than
needlessly swapping domains.

Signed-off-by: Tom Murphy <murphyt7@tcd.ie>
---
drivers/iommu/intel-iommu.c | 88 +++++++++++++------------------------
1 file changed, 31 insertions(+), 57 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 0c8d81f56a30..c1ea66467918 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3462,46 +3462,9 @@ static struct dmar_domain *get_private_domain_for_dev(struct device *dev)
}

/* Check if the dev needs to go through non-identity map and unmap process.*/
-static bool iommu_need_mapping(struct device *dev)
+static bool iommu_no_mapping(struct device *dev)
{
- int ret;
-
- if (iommu_dummy(dev))
- return false;
-
- ret = identity_mapping(dev);
- if (ret) {
- u64 dma_mask = *dev->dma_mask;
-
- if (dev->coherent_dma_mask && dev->coherent_dma_mask < dma_mask)
- dma_mask = dev->coherent_dma_mask;
-
- if (dma_mask >= dma_direct_get_required_mask(dev))
- return false;
-
- /*
- * 32 bit DMA is removed from si_domain and fall back to
- * non-identity mapping.
- */
- dmar_remove_one_dev_info(dev);
- ret = iommu_request_dma_domain_for_dev(dev);
- if (ret) {
- struct iommu_domain *domain;
- struct dmar_domain *dmar_domain;
-
- domain = iommu_get_domain_for_dev(dev);
- if (domain) {
- dmar_domain = to_dmar_domain(domain);
- dmar_domain->flags |= DOMAIN_FLAG_LOSE_CHILDREN;
- }
- dmar_remove_one_dev_info(dev);
- get_private_domain_for_dev(dev);
- }
-
- dev_info(dev, "32bit DMA uses non-identity mapping\n");
- }
-
- return true;
+ return iommu_dummy(dev) || identity_mapping(dev);
}

static dma_addr_t __intel_map_single(struct device *dev, phys_addr_t paddr,
@@ -3568,20 +3531,22 @@ static dma_addr_t intel_map_page(struct device *dev, struct page *page,
enum dma_data_direction dir,
unsigned long attrs)
{
- if (iommu_need_mapping(dev))
- return __intel_map_single(dev, page_to_phys(page) + offset,
- size, dir, *dev->dma_mask);
- return dma_direct_map_page(dev, page, offset, size, dir, attrs);
+ if (iommu_no_mapping(dev))
+ return dma_direct_map_page(dev, page, offset, size, dir, attrs);
+
+ return __intel_map_single(dev, page_to_phys(page) + offset, size, dir,
+ *dev->dma_mask);
}

static dma_addr_t intel_map_resource(struct device *dev, phys_addr_t phys_addr,
size_t size, enum dma_data_direction dir,
unsigned long attrs)
{
- if (iommu_need_mapping(dev))
- return __intel_map_single(dev, phys_addr, size, dir,
- *dev->dma_mask);
- return dma_direct_map_resource(dev, phys_addr, size, dir, attrs);
+ if (iommu_no_mapping(dev))
+ return dma_direct_map_resource(dev, phys_addr, size, dir,
+ attrs);
+
+ return __intel_map_single(dev, phys_addr, size, dir, *dev->dma_mask);
}

static void intel_unmap(struct device *dev, dma_addr_t dev_addr, size_t size)
@@ -3632,16 +3597,16 @@ static void intel_unmap_page(struct device *dev, dma_addr_t dev_addr,
size_t size, enum dma_data_direction dir,
unsigned long attrs)
{
- if (iommu_need_mapping(dev))
- intel_unmap(dev, dev_addr, size);
- else
+ if (iommu_no_mapping(dev))
dma_direct_unmap_page(dev, dev_addr, size, dir, attrs);
+ else
+ intel_unmap(dev, dev_addr, size);
}

static void intel_unmap_resource(struct device *dev, dma_addr_t dev_addr,
size_t size, enum dma_data_direction dir, unsigned long attrs)
{
- if (iommu_need_mapping(dev))
+ if (!iommu_no_mapping(dev))
intel_unmap(dev, dev_addr, size);
}

@@ -3652,7 +3617,7 @@ static void *intel_alloc_coherent(struct device *dev, size_t size,
struct page *page = NULL;
int order;

- if (!iommu_need_mapping(dev))
+ if (iommu_no_mapping(dev))
return dma_direct_alloc(dev, size, dma_handle, flags, attrs);

size = PAGE_ALIGN(size);
@@ -3688,7 +3653,7 @@ static void intel_free_coherent(struct device *dev, size_t size, void *vaddr,
int order;
struct page *page = virt_to_page(vaddr);

- if (!iommu_need_mapping(dev))
+ if (iommu_no_mapping(dev))
return dma_direct_free(dev, size, vaddr, dma_handle, attrs);

size = PAGE_ALIGN(size);
@@ -3708,7 +3673,7 @@ static void intel_unmap_sg(struct device *dev, struct scatterlist *sglist,
struct scatterlist *sg;
int i;

- if (!iommu_need_mapping(dev))
+ if (iommu_no_mapping(dev))
return dma_direct_unmap_sg(dev, sglist, nelems, dir, attrs);

for_each_sg(sglist, sg, nelems, i) {
@@ -3734,7 +3699,7 @@ static int intel_map_sg(struct device *dev, struct scatterlist *sglist, int nele
struct intel_iommu *iommu;

BUG_ON(dir == DMA_NONE);
- if (!iommu_need_mapping(dev))
+ if (iommu_no_mapping(dev))
return dma_direct_map_sg(dev, sglist, nelems, dir, attrs);

domain = deferred_attach_domain(dev);
@@ -3782,7 +3747,7 @@ static int intel_map_sg(struct device *dev, struct scatterlist *sglist, int nele

static u64 intel_get_required_mask(struct device *dev)
{
- if (!iommu_need_mapping(dev))
+ if (iommu_no_mapping(dev))
return dma_direct_get_required_mask(dev);
return DMA_BIT_MASK(32);
}
@@ -5618,9 +5583,13 @@ static int intel_iommu_add_device(struct device *dev)
struct iommu_domain *domain;
struct intel_iommu *iommu;
struct iommu_group *group;
+ u64 dma_mask = *dev->dma_mask;
u8 bus, devfn;
int ret;

+ if (dev->coherent_dma_mask && dev->coherent_dma_mask < dma_mask)
+ dma_mask = dev->coherent_dma_mask;
+
iommu = device_to_iommu(dev, &bus, &devfn);
if (!iommu)
return -ENODEV;
@@ -5640,7 +5609,12 @@ static int intel_iommu_add_device(struct device *dev)
domain = iommu_get_domain_for_dev(dev);
dmar_domain = to_dmar_domain(domain);
if (domain->type == IOMMU_DOMAIN_DMA) {
- if (device_def_domain_type(dev) == IOMMU_DOMAIN_IDENTITY) {
+ /*
+ * We check dma_mask >= dma_get_required_mask(dev) because
+ * 32 bit DMA falls back to non-identity mapping.
+ */
+ if (device_def_domain_type(dev) == IOMMU_DOMAIN_IDENTITY &&
+ dma_mask >= dma_get_required_mask(dev)) {
ret = iommu_request_dm_for_dev(dev);
if (ret) {
dmar_remove_one_dev_info(dev);
--
2.20.1