Commit 44401a20 authored by Maciej S. Szmigiero's avatar Maciej S. Szmigiero Committed by Paolo Bonzini
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KVM: Optimize overlapping memslots check 



Do a quick lookup for possibly overlapping gfns when creating or moving
a memslot instead of performing a linear scan of the whole memslot set.

Signed-off-by: default avatarMaciej S. Szmigiero <maciej.szmigiero@oracle.com>
[sean: tweaked params to avoid churn in future cleanup]
Reviewed-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <a4795e5c2f624754e9c0aab023ebda1966feb3e1.1638817641.git.maciej.szmigiero@oracle.com>
parent f4209439

virt/kvm/kvm_main.c

+22 −14
Original line number Diff line number Diff line
@@ -1815,6 +1815,19 @@ static int kvm_set_memslot(struct kvm *kvm, 
	return 0;

}



static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id,

				      gfn_t start, gfn_t end)

{

	struct kvm_memslot_iter iter;



	kvm_for_each_memslot_in_gfn_range(&iter, slots, start, end) {

		if (iter.slot->id != id)

			return true;

	}



	return false;

}



/*

 * Allocate some memory and give it an address in the guest physical address

 * space.
@@ -1826,8 +1839,9 @@ static int kvm_set_memslot(struct kvm *kvm, 
int __kvm_set_memory_region(struct kvm *kvm,

			    const struct kvm_userspace_memory_region *mem)

{

	struct kvm_memory_slot *old, *tmp;

	struct kvm_memory_slot *old;

	struct kvm_memory_slot new;

	struct kvm_memslots *slots;

	enum kvm_mr_change change;

	int as_id, id;

	int r;
@@ -1856,11 +1870,13 @@ int __kvm_set_memory_region(struct kvm *kvm, 
	if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)

		return -EINVAL;



	slots = __kvm_memslots(kvm, as_id);



	/*

	 * Note, the old memslot (and the pointer itself!) may be invalidated

	 * and/or destroyed by kvm_set_memslot().

	 */

	old = id_to_memslot(__kvm_memslots(kvm, as_id), id);

	old = id_to_memslot(slots, id);



	if (!mem->memory_size) {

		if (!old || !old->npages)
@@ -1909,18 +1925,10 @@ int __kvm_set_memory_region(struct kvm *kvm, 
			return 0;

	}



	if ((change == KVM_MR_CREATE) || (change == KVM_MR_MOVE)) {

		int bkt;



		/* Check for overlaps */

		kvm_for_each_memslot(tmp, bkt, __kvm_memslots(kvm, as_id)) {

			if (tmp->id == id)

				continue;

			if (!((new.base_gfn + new.npages <= tmp->base_gfn) ||

			      (new.base_gfn >= tmp->base_gfn + tmp->npages)))

	if ((change == KVM_MR_CREATE || change == KVM_MR_MOVE) &&

	    kvm_check_memslot_overlap(slots, id, new.base_gfn,

				      new.base_gfn + new.npages))

		return -EEXIST;

		}

	}



	return kvm_set_memslot(kvm, old, &new, change);

}