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KVM: x86/mmu: Zap only the relevant pages when removing a memslot 

Modify kvm_mmu_invalidate_zap_pages_in_memslot(), a.k.a. the x86 MMU's
handler for kvm_arch_flush_shadow_memslot(), to zap only the pages/PTEs
that actually belong to the memslot being removed.  This improves
performance, especially why the deleted memslot has only a few shadow
entries, or even no entries.  E.g. a microbenchmark to access regular
memory while concurrently reading PCI ROM to trigger memslot deletion
showed a 5% improvement in throughput.

Cc: Xiao Guangrong <guangrong.xiao@gmail.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2019-02-05 13:01:21 -08:00 committed by Paolo Bonzini
parent a21136345c
commit 4e103134b8
1 changed files with 32 additions and 1 deletions
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33
arch/x86/kvm/mmu.c
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@ -5622,7 +5622,38 @@ static void kvm_mmu_invalidate_zap_pages_in_memslot(struct kvm *kvm,
struct kvm_memory_slot *slot,
struct kvm_page_track_notifier_node *node)
{
kvm_mmu_invalidate_zap_all_pages(kvm);
struct kvm_mmu_page *sp;
LIST_HEAD(invalid_list);
unsigned long i;
bool flush;
gfn_t gfn;
spin_lock(&kvm->mmu_lock);
if (list_empty(&kvm->arch.active_mmu_pages))
goto out_unlock;
flush = slot_handle_all_level(kvm, slot, kvm_zap_rmapp, false);
for (i = 0; i < slot->npages; i++) {
gfn = slot->base_gfn + i;
for_each_valid_sp(kvm, sp, gfn) {
if (sp->gfn != gfn)
continue;
kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list);
}
if (need_resched() || spin_needbreak(&kvm->mmu_lock)) {
kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush);
flush = false;
cond_resched_lock(&kvm->mmu_lock);
}
}
kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush);
out_unlock:
spin_unlock(&kvm->mmu_lock);
}
void kvm_mmu_init_vm(struct kvm *kvm)