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Commit 5225fdf8 authored by Takuya Yoshikawa's avatar Takuya Yoshikawa Committed by Paolo Bonzini
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KVM: x86: MMU: Eliminate an extra memory slot search in mapping_level() 



Calling kvm_vcpu_gfn_to_memslot() twice in mapping_level() should be
avoided since getting a slot by binary search may not be negligible,
especially for virtual machines with many memory slots.

Signed-off-by: default avatarTakuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent d8aacf5d

arch/x86/kvm/mmu.c

+11 −6
Original line number Diff line number Diff line
@@ -818,14 +818,11 @@ static void unaccount_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp) 
	kvm->arch.indirect_shadow_pages--;

}



static int has_wrprotected_page(struct kvm_vcpu *vcpu,

				gfn_t gfn,

				int level)

static int __has_wrprotected_page(gfn_t gfn, int level,

				  struct kvm_memory_slot *slot)

{

	struct kvm_memory_slot *slot;

	struct kvm_lpage_info *linfo;



	slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);

	if (slot) {

		linfo = lpage_info_slot(gfn, slot, level);

		return linfo->write_count;
@@ -834,6 +831,14 @@ static int has_wrprotected_page(struct kvm_vcpu *vcpu, 
	return 1;

}



static int has_wrprotected_page(struct kvm_vcpu *vcpu, gfn_t gfn, int level)

{

	struct kvm_memory_slot *slot;



	slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);

	return __has_wrprotected_page(gfn, level, slot);

}



static int host_mapping_level(struct kvm *kvm, gfn_t gfn)

{

	unsigned long page_size;
@@ -896,7 +901,7 @@ static int mapping_level(struct kvm_vcpu *vcpu, gfn_t large_gfn, 
	max_level = min(kvm_x86_ops->get_lpage_level(), host_level);



	for (level = PT_DIRECTORY_LEVEL; level <= max_level; ++level)

		if (has_wrprotected_page(vcpu, large_gfn, level))

		if (__has_wrprotected_page(large_gfn, level, slot))

			break;



	return level - 1;