KVM: x86/mmu: Reduce the update to the spte in FNAME(sync_spte)

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Sometimes when the guest updates its pagetable, it adds only new gptes
to it without changing any existed one, so there is no point to update
the sptes for these existed gptes.

Also when the sptes for these unchanged gptes are updated, the AD
bits are also removed since make_spte() is called with prefetch=true
which might result unneeded TLB flushing.

Just do nothing if the gpte's permissions are unchanged.

Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Link: https://lore.kernel.org/r/20230216154115.710033-7-jiangshanlai@gmail.com
[sean: expand comment to call out A/D bits]
Signed-off-by: Sean Christopherson <seanjc@google.com>

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Lai Jiangshan 2023-02-16 23:41:12 +08:00 • committed by Sean Christopherson

parent c3c6c9fc5d

commit e6722d9211

1 changed files with 8 additions and 0 deletions

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arch/x86/kvm/mmu/paging_tmpl.h

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