diff options
| author | Robin Murphy <robin.murphy@arm.com> | 2018-09-12 16:24:12 +0100 |
|---|---|---|
| committer | Joerg Roedel <jroedel@suse.de> | 2018-09-25 10:23:16 +0200 |
| commit | 6af588fed39178c8e118fcf9cb6664e58a1fbe88 (patch) | |
| tree | 1d204c47e1b8e24936d8015ff6013228880dbc72 /include/linux/iommu.h | |
| parent | bee60e94a1e20ec0b8ffdafae270731d8fda4551 (diff) | |
iommu: Add fast hook for getting DMA domains
While iommu_get_domain_for_dev() is the robust way for arbitrary IOMMU
API callers to retrieve the domain pointer, for DMA ops domains it
doesn't scale well for large systems and multi-queue devices, since the
momentary refcount adjustment will lead to exclusive cacheline contention
when multiple CPUs are operating in parallel on different mappings for
the same device.
In the case of DMA ops domains, however, this refcounting is actually
unnecessary, since they already imply that the group exists and is
managed by platform code and IOMMU internals (by virtue of
iommu_group_get_for_dev()) such that a reference will already be held
for the lifetime of the device. Thus we can avoid the bottleneck by
providing a fast lookup specifically for the DMA code to retrieve the
default domain it already knows it has set up - a simple read-only
dereference plays much nicer with cache-coherency protocols.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Tested-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Diffstat (limited to 'include/linux/iommu.h')
| -rw-r--r-- | include/linux/iommu.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/iommu.h b/include/linux/iommu.h index 87994c265bf5..c783648d4060 100644 --- a/include/linux/iommu.h +++ b/include/linux/iommu.h @@ -293,6 +293,7 @@ extern int iommu_attach_device(struct iommu_domain *domain, extern void iommu_detach_device(struct iommu_domain *domain, struct device *dev); extern struct iommu_domain *iommu_get_domain_for_dev(struct device *dev); +extern struct iommu_domain *iommu_get_dma_domain(struct device *dev); extern int iommu_map(struct iommu_domain *domain, unsigned long iova, phys_addr_t paddr, size_t size, int prot); extern size_t iommu_unmap(struct iommu_domain *domain, unsigned long iova, |