diff options
| author | Lai Jiangshan <laijs@cn.fujitsu.com> | 2010-05-26 16:49:59 +0800 |
|---|---|---|
| committer | Avi Kivity <avi@redhat.com> | 2010-08-01 10:35:52 +0300 |
| commit | 2032a93d66fa282ba0f2ea9152eeff9511fa9a96 (patch) | |
| tree | f0bbd50c3f237fa93c87207dc29602cbdcf9ad63 /Documentation/kvm/mmu.txt | |
| parent | c8174f7b35b3018c4c7b3237ed1c792e454fd5c3 (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/mmu.txt')
| -rw-r--r-- | Documentation/kvm/mmu.txt | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/Documentation/kvm/mmu.txt b/Documentation/kvm/mmu.txt index 0e872ae30914..2201dcba92a1 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 |