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Diffstat (limited to 'Documentation/virt/kvm/locking.rst')
| -rw-r--r-- | Documentation/virt/kvm/locking.rst | 11 |
1 files changed, 5 insertions, 6 deletions
diff --git a/Documentation/virt/kvm/locking.rst b/Documentation/virt/kvm/locking.rst index c02291beac3f..b21a34c34a21 100644 --- a/Documentation/virt/kvm/locking.rst +++ b/Documentation/virt/kvm/locking.rst @@ -96,19 +96,18 @@ will happen: We dirty-log for gfn1, that means gfn2 is lost in dirty-bitmap. For direct sp, we can easily avoid it since the spte of direct sp is fixed -to gfn. For indirect sp, before we do cmpxchg, we call gfn_to_pfn_atomic() -to pin gfn to pfn, because after gfn_to_pfn_atomic(): +to gfn. For indirect sp, we disabled fast page fault for simplicity. + +A solution for indirect sp could be to pin the gfn, for example via +kvm_vcpu_gfn_to_pfn_atomic, before the cmpxchg. After the pinning: - We have held the refcount of pfn that means the pfn can not be freed and be reused for another gfn. -- The pfn is writable that means it can not be shared between different gfns +- The pfn is writable and therefore it cannot be shared between different gfns by KSM. Then, we can ensure the dirty bitmaps is correctly set for a gfn. -Currently, to simplify the whole things, we disable fast page fault for -indirect shadow page. - 2) Dirty bit tracking In the origin code, the spte can be fast updated (non-atomically) if the |