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KVM: X86: Optimize zapping rmap

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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: Peter Xu <peterx@redhat.com>
Message-Id: <20210730220605.26377-1-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Peter Xu 2021-07-30 18:06:05 -04:00 committed by Paolo Bonzini
parent 13236e25eb
commit a75b540451
1 changed files with 29 additions and 12 deletions
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41
arch/x86/kvm/mmu/mmu.c
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@ -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,