Commit a75b5404 authored by Peter Xu's avatar Peter Xu Committed by Paolo Bonzini
Browse files

KVM: X86: Optimize zapping rmap 



Using rmap_get_first() and rmap_remove() for zapping a huge rmap list could be
slow.  The easy way is to travers the rmap list, collecting the a/d bits and
free the slots along the way.

Provide a pte_list_destroy() and do exactly that.

Signed-off-by: default avatarPeter Xu <peterx@redhat.com>
Message-Id: <20210730220605.26377-1-peterx@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 13236e25

arch/x86/kvm/mmu/mmu.c

+29 −12
Original line number Diff line number Diff line
@@ -1007,6 +1007,34 @@ static void pte_list_remove(struct kvm_rmap_head *rmap_head, u64 *sptep) 
	__pte_list_remove(sptep, rmap_head);

}



/* Return true if rmap existed, false otherwise */

static bool pte_list_destroy(struct kvm_rmap_head *rmap_head)

{

	struct pte_list_desc *desc, *next;

	int i;



	if (!rmap_head->val)

		return false;



	if (!(rmap_head->val & 1)) {

		mmu_spte_clear_track_bits((u64 *)rmap_head->val);

		goto out;

	}



	desc = (struct pte_list_desc *)(rmap_head->val & ~1ul);



	for (; desc; desc = next) {

		for (i = 0; i < desc->spte_count; i++)

			mmu_spte_clear_track_bits(desc->sptes[i]);

		next = desc->more;

		mmu_free_pte_list_desc(desc);

	}

out:

	/* rmap_head is meaningless now, remember to reset it */

	rmap_head->val = 0;

	return true;

}



static struct kvm_rmap_head *__gfn_to_rmap(gfn_t gfn, int level,

					   const struct kvm_memory_slot *slot)

{
@@ -1398,18 +1426,7 @@ static bool rmap_write_protect(struct kvm_vcpu *vcpu, u64 gfn) 
static bool kvm_zap_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head,

			  const struct kvm_memory_slot *slot)

{

	u64 *sptep;

	struct rmap_iterator iter;

	bool flush = false;



	while ((sptep = rmap_get_first(rmap_head, &iter))) {

		rmap_printk("spte %p %llx.\n", sptep, *sptep);



		pte_list_remove(rmap_head, sptep);

		flush = true;

	}



	return flush;

	return pte_list_destroy(rmap_head);

}



static bool kvm_unmap_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head,