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-rw-r--r--Documentation/cachetlb.txt30
1 files changed, 27 insertions, 3 deletions
diff --git a/Documentation/cachetlb.txt b/Documentation/cachetlb.txt
index da42ab414c48..2b5f823abd03 100644
--- a/Documentation/cachetlb.txt
+++ b/Documentation/cachetlb.txt
@@ -88,12 +88,12 @@ changes occur:
This is used primarily during fault processing.
5) void update_mmu_cache(struct vm_area_struct *vma,
- unsigned long address, pte_t pte)
+ unsigned long address, pte_t *ptep)
At the end of every page fault, this routine is invoked to
tell the architecture specific code that a translation
- described by "pte" now exists at virtual address "address"
- for address space "vma->vm_mm", in the software page tables.
+ now exists at virtual address "address" for address space
+ "vma->vm_mm", in the software page tables.
A port may use this information in any way it so chooses.
For example, it could use this event to pre-load TLB
@@ -377,3 +377,27 @@ maps this page at its virtual address.
All the functionality of flush_icache_page can be implemented in
flush_dcache_page and update_mmu_cache. In 2.7 the hope is to
remove this interface completely.
+
+The final category of APIs is for I/O to deliberately aliased address
+ranges inside the kernel. Such aliases are set up by use of the
+vmap/vmalloc API. Since kernel I/O goes via physical pages, the I/O
+subsystem assumes that the user mapping and kernel offset mapping are
+the only aliases. This isn't true for vmap aliases, so anything in
+the kernel trying to do I/O to vmap areas must manually manage
+coherency. It must do this by flushing the vmap range before doing
+I/O and invalidating it after the I/O returns.
+
+ void flush_kernel_vmap_range(void *vaddr, int size)
+ flushes the kernel cache for a given virtual address range in
+ the vmap area. This is to make sure that any data the kernel
+ modified in the vmap range is made visible to the physical
+ page. The design is to make this area safe to perform I/O on.
+ Note that this API does *not* also flush the offset map alias
+ of the area.
+
+ void invalidate_kernel_vmap_range(void *vaddr, int size) invalidates
+ the cache for a given virtual address range in the vmap area
+ which prevents the processor from making the cache stale by
+ speculatively reading data while the I/O was occurring to the
+ physical pages. This is only necessary for data reads into the
+ vmap area.