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authorAlex Williamson <alex.williamson@redhat.com>2012-12-10 10:33:03 -0700
committerMarcelo Tosatti <mtosatti@redhat.com>2012-12-13 23:21:53 -0200
commitb7f69c555ca430129b6cde81e9f0927531420c5c (patch)
tree7b325611705e6293ce1fe3c87eeeb30746e2fe0e /virt
parente40f193f5bb022e927a57a4f5d5194e4f12ddb74 (diff)
downloadlinux-b7f69c555ca430129b6cde81e9f0927531420c5c.tar.gz
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>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/kvm_main.c21
1 files changed, 14 insertions, 7 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 9a56ca2fa25..4c8c0657e37 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -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) {