KVM: MMU: Don't allocate gfns page for direct mmu pages

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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>

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Lai Jiangshan 2010-05-26 16:49:59 +08:00 • committed by Avi Kivity

parent c8174f7b35

commit 2032a93d66

3 changed files with 35 additions and 10 deletions

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38

arch/x86/kvm/mmu.c

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3

arch/x86/kvm/paging_tmpl.h

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