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authorLai Jiangshan <laijs@cn.fujitsu.com>2010-05-26 16:49:59 +0800
committerAvi Kivity <avi@redhat.com>2010-08-01 10:35:52 +0300
commit2032a93d66fa282ba0f2ea9152eeff9511fa9a96 (patch)
treef0bbd50c3f237fa93c87207dc29602cbdcf9ad63 /Documentation/kvm
parentc8174f7b35b3018c4c7b3237ed1c792e454fd5c3 (diff)
KVM: MMU: Don't allocate gfns page for direct mmu pages
When sp->role.direct is set, sp->gfns does not contain any essential information, leaf sptes reachable from this sp are for a continuous guest physical memory range (a linear range). So sp->gfns[i] (if it was set) equals to sp->gfn + i. (PT_PAGE_TABLE_LEVEL) Obviously, it is not essential information, we can calculate it when need. It means we don't need sp->gfns when sp->role.direct=1, Thus we can save one page usage for every kvm_mmu_page. Note: Access to sp->gfns must be wrapped by kvm_mmu_page_get_gfn() or kvm_mmu_page_set_gfn(). It is only exposed in FNAME(sync_page). Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'Documentation/kvm')
-rw-r--r--Documentation/kvm/mmu.txt4
1 files changed, 3 insertions, 1 deletions
diff --git a/Documentation/kvm/mmu.txt b/Documentation/kvm/mmu.txt
index 0e872ae3091..2201dcba92a 100644
--- a/Documentation/kvm/mmu.txt
+++ b/Documentation/kvm/mmu.txt
@@ -180,7 +180,9 @@ Shadow pages contain the following information:
guest pages as leaves.
gfns:
An array of 512 guest frame numbers, one for each present pte. Used to
- perform a reverse map from a pte to a gfn.
+ perform a reverse map from a pte to a gfn. When role.direct is set, any
+ element of this array can be calculated from the gfn field when used, in
+ this case, the array of gfns is not allocated. See role.direct and gfn.
slot_bitmap:
A bitmap containing one bit per memory slot. If the page contains a pte
mapping a page from memory slot n, then bit n of slot_bitmap will be set