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KVM: MMU: using __xchg_spte more smarter

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Sometimes, atomically set spte is not needed, this patch call __xchg_spte()
more smartly

Note: if the old mapping's access bit is already set, we no need atomic operation
since the access bit is not lost

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Xiao Guangrong 2010-07-16 11:30:18 +08:00 committed by Avi Kivity
parent e4b502ead2
commit 9a3aad7057
1 changed files with 7 additions and 2 deletions
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9
arch/x86/kvm/mmu.c
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@ -682,9 +682,14 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
static void set_spte_track_bits(u64 *sptep, u64 new_spte)
{
pfn_t pfn;
u64 old_spte;
u64 old_spte = *sptep;
if (!shadow_accessed_mask || !is_shadow_present_pte(old_spte) ||
old_spte & shadow_accessed_mask) {
__set_spte(sptep, new_spte);
} else
old_spte = __xchg_spte(sptep, new_spte);
old_spte = __xchg_spte(sptep, new_spte);
if (!is_rmap_spte(old_spte))
return;
pfn = spte_to_pfn(old_spte);