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Commit b7f69c55 authored by Alex Williamson's avatar Alex Williamson Committed by Marcelo Tosatti
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KVM: Minor memory slot optimization 



If a slot is removed or moved in the guest physical address space, we
first allocate and install a new slot array with the invalidated
entry.  The old array is then freed.  We then proceed to allocate yet
another slot array to install the permanent replacement.  Re-use the
original array when this occurs and avoid the extra kfree/kmalloc.

Reviewed-by: default avatarGleb Natapov <gleb@redhat.com>
Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent e40f193f

virt/kvm/kvm_main.c

+14 −7
Original line number Diff line number Diff line
@@ -716,7 +716,7 @@ int __kvm_set_memory_region(struct kvm *kvm, 
	unsigned long npages;

	struct kvm_memory_slot *memslot, *slot;

	struct kvm_memory_slot old, new;

	struct kvm_memslots *slots, *old_memslots;

	struct kvm_memslots *slots = NULL, *old_memslots;



	r = check_memory_region_flags(mem);

	if (r)
@@ -832,18 +832,25 @@ int __kvm_set_memory_region(struct kvm *kvm, 
		 * 	- kvm_is_visible_gfn (mmu_check_roots)

		 */

		kvm_arch_flush_shadow_memslot(kvm, slot);

		kfree(old_memslots);

		slots = old_memslots;

	}



	r = kvm_arch_prepare_memory_region(kvm, &new, old, mem, user_alloc);

	if (r)

		goto out_free;

		goto out_slots;



	r = -ENOMEM;

	/*

	 * We can re-use the old_memslots from above, the only difference

	 * from the currently installed memslots is the invalid flag.  This

	 * will get overwritten by update_memslots anyway.

	 */

	if (!slots) {

		slots = kmemdup(kvm->memslots, sizeof(struct kvm_memslots),

				GFP_KERNEL);

		if (!slots)

			goto out_free;

	}



	/* map new memory slot into the iommu */

	if (npages) {