An iova range may contain many pages/blocks, especially for the case of
unmap_sg. Currently, for each page/block unmapping, a tlb invalidation
operation will be followed and wait(called tlb_sync) until the operation's
over. But actually we only need one tlb_sync in the last stage. Look at
the loop in function iommu_unmap:
while (unmapped < size) {
...
unmapped_page = domain->ops->unmap(domain, iova, pgsize);
...
}
It's not a good idea to add the tlb_sync in domain->ops->unmap.
There are many profits, below actions can be reduced:
1. iommu hardware is a shared resource for cpus, for the tlb_sync operation,
lock protection is needed.
2. iommu hardware is not inside CPU, to start tlb_sync and check it finished
may take a lot of time.
Some people might ask: Is it safe to do so? The answer is yes. The standard
processing flow is:
alloc iova
map
process data
unmap
tlb invalidation and sync
free iova
What should be guaranteed is: "free iova" action is behind "unmap" and "tlbi
operation" action, that is what we are doing right now. This ensures that:
all TLBs of an iova-range have been invalidated before the iova reallocated.
Signed-off-by: Zhen Lei <thunder.leiz...@huawei.com>
---
drivers/iommu/iommu.c | 3 +++
include/linux/iommu.h | 1 +
2 files changed, 4 insertions(+)
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index cf7ca7e..01e91a8 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1610,6 +1610,9 @@ size_t iommu_unmap(struct iommu_domain *domain, unsigned
long iova, size_t size)
unmapped += unmapped_page;
}
+ if (domain->ops->unmap_tlb_sync)
+ domain->ops->unmap_tlb_sync(domain);
+
trace_unmap(orig_iova, size, unmapped);
return unmapped;
}
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 2cb54ad..5964121 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -197,6 +197,7 @@ struct iommu_ops {
phys_addr_t paddr, size_t size, int prot);
size_t (*unmap)(struct iommu_domain *domain, unsigned long iova,
size_t size);
+ void (*unmap_tlb_sync)(struct iommu_domain *domain);
size_t (*map_sg)(struct iommu_domain *domain, unsigned long iova,
struct scatterlist *sg, unsigned int nents, int prot);
phys_addr_t (*iova_to_phys)(struct iommu_domain *domain, dma_addr_t
iova);
--
2.5.0
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