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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: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Alex Williamson 2012-12-10 10:33:03 -07:00 committed by Marcelo Tosatti
parent e40f193f5b
commit b7f69c555c
1 changed files with 14 additions and 7 deletions
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21
virt/kvm/kvm_main.c
View File

@ -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;
slots = kmemdup(kvm->memslots, sizeof(struct kvm_memslots),
GFP_KERNEL);
if (!slots)
goto out_free;
/*
* 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) {