1 files changed, 0 insertions, 93 deletions
diff --git a/Documentation/vm/mmu_notifier.txt b/Documentation/vm/mmu_notifier.txt
deleted file mode 100644
index 23b462566bb76..0000000000000
--- a/Documentation/vm/mmu_notifier.txt
+++ /dev/null
@@ -1,93 +0,0 @@
-When do you need to notify inside page table lock ?
-
-When clearing a pte/pmd we are given a choice to notify the event through
-(notify version of *_clear_flush call mmu_notifier_invalidate_range) under
-the page table lock. But that notification is not necessary in all cases.
-
-For secondary TLB (non CPU TLB) like IOMMU TLB or device TLB (when device use
-thing like ATS/PASID to get the IOMMU to walk the CPU page table to access a
-process virtual address space). There is only 2 cases when you need to notify
-those secondary TLB while holding page table lock when clearing a pte/pmd:
-
-  A) page backing address is free before mmu_notifier_invalidate_range_end()
-  B) a page table entry is updated to point to a new page (COW, write fault
-     on zero page, __replace_page(), ...)
-
-Case A is obvious you do not want to take the risk for the device to write to
-a page that might now be used by some completely different task.
-
-Case B is more subtle. For correctness it requires the following sequence to
-happen:
-  - take page table lock
-  - clear page table entry and notify ([pmd/pte]p_huge_clear_flush_notify())
-  - set page table entry to point to new page
-
-If clearing the page table entry is not followed by a notify before setting
-the new pte/pmd value then you can break memory model like C11 or C++11 for
-the device.
-
-Consider the following scenario (device use a feature similar to ATS/PASID):
-
-Two address addrA and addrB such that |addrA - addrB| >= PAGE_SIZE we assume
-they are write protected for COW (other case of B apply too).
-
-[Time N] --------------------------------------------------------------------
-CPU-thread-0  {try to write to addrA}
-CPU-thread-1  {try to write to addrB}
-CPU-thread-2  {}
-CPU-thread-3  {}
-DEV-thread-0  {read addrA and populate device TLB}
-DEV-thread-2  {read addrB and populate device TLB}
-[Time N+1] ------------------------------------------------------------------
-CPU-thread-0  {COW_step0: {mmu_notifier_invalidate_range_start(addrA)}}
-CPU-thread-1  {COW_step0: {mmu_notifier_invalidate_range_start(addrB)}}
-CPU-thread-2  {}
-CPU-thread-3  {}
-DEV-thread-0  {}
-DEV-thread-2  {}
-[Time N+2] ------------------------------------------------------------------
-CPU-thread-0  {COW_step1: {update page table to point to new page for addrA}}
-CPU-thread-1  {COW_step1: {update page table to point to new page for addrB}}
-CPU-thread-2  {}
-CPU-thread-3  {}
-DEV-thread-0  {}
-DEV-thread-2  {}
-[Time N+3] ------------------------------------------------------------------
-CPU-thread-0  {preempted}
-CPU-thread-1  {preempted}
-CPU-thread-2  {write to addrA which is a write to new page}
-CPU-thread-3  {}
-DEV-thread-0  {}
-DEV-thread-2  {}
-[Time N+3] ------------------------------------------------------------------
-CPU-thread-0  {preempted}
-CPU-thread-1  {preempted}
-CPU-thread-2  {}
-CPU-thread-3  {write to addrB which is a write to new page}
-DEV-thread-0  {}
-DEV-thread-2  {}
-[Time N+4] ------------------------------------------------------------------
-CPU-thread-0  {preempted}
-CPU-thread-1  {COW_step3: {mmu_notifier_invalidate_range_end(addrB)}}
-CPU-thread-2  {}
-CPU-thread-3  {}
-DEV-thread-0  {}
-DEV-thread-2  {}
-[Time N+5] ------------------------------------------------------------------
-CPU-thread-0  {preempted}
-CPU-thread-1  {}
-CPU-thread-2  {}
-CPU-thread-3  {}
-DEV-thread-0  {read addrA from old page}
-DEV-thread-2  {read addrB from new page}
-
-So here because at time N+2 the clear page table entry was not pair with a
-notification to invalidate the secondary TLB, the device see the new value for
-addrB before seing the new value for addrA. This break total memory ordering
-for the device.
-
-When changing a pte to write protect or to point to a new write protected page
-with same content (KSM) it is fine to delay the mmu_notifier_invalidate_range
-call to mmu_notifier_invalidate_range_end() outside the page table lock. This
-is true even if the thread doing the page table update is preempted right after
-releasing page table lock but before call mmu_notifier_invalidate_range_end().