Commit b7f69c555ca430129b6cde81e9f0927531420c5c
Committed by
Marcelo Tosatti
Marcelo Tosatti
1 parent
e40f193f5b
Exists in
smarc-l5.0.0_1.0.0-ga
and in
5 other branches
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>
Showing 1 changed file with 14 additions and 7 deletions Side-by-side Diff
virt/kvm/kvm_main.c
| ... | ... | @@ -716,7 +716,7 @@ |
| 716 | 716 | unsigned long npages; |
| 717 | 717 | struct kvm_memory_slot *memslot, *slot; |
| 718 | 718 | struct kvm_memory_slot old, new; |
| 719 | - struct kvm_memslots *slots, *old_memslots; | |
| 719 | + struct kvm_memslots *slots = NULL, *old_memslots; | |
| 720 | 720 | |
| 721 | 721 | r = check_memory_region_flags(mem); |
| 722 | 722 | if (r) |
| 723 | 723 | |
| 724 | 724 | |
| ... | ... | @@ -832,18 +832,25 @@ |
| 832 | 832 | * - kvm_is_visible_gfn (mmu_check_roots) |
| 833 | 833 | */ |
| 834 | 834 | kvm_arch_flush_shadow_memslot(kvm, slot); |
| 835 | - kfree(old_memslots); | |
| 835 | + slots = old_memslots; | |
| 836 | 836 | } |
| 837 | 837 | |
| 838 | 838 | r = kvm_arch_prepare_memory_region(kvm, &new, old, mem, user_alloc); |
| 839 | 839 | if (r) |
| 840 | - goto out_free; | |
| 840 | + goto out_slots; | |
| 841 | 841 | |
| 842 | 842 | r = -ENOMEM; |
| 843 | - slots = kmemdup(kvm->memslots, sizeof(struct kvm_memslots), | |
| 844 | - GFP_KERNEL); | |
| 845 | - if (!slots) | |
| 846 | - goto out_free; | |
| 843 | + /* | |
| 844 | + * We can re-use the old_memslots from above, the only difference | |
| 845 | + * from the currently installed memslots is the invalid flag. This | |
| 846 | + * will get overwritten by update_memslots anyway. | |
| 847 | + */ | |
| 848 | + if (!slots) { | |
| 849 | + slots = kmemdup(kvm->memslots, sizeof(struct kvm_memslots), | |
| 850 | + GFP_KERNEL); | |
| 851 | + if (!slots) | |
| 852 | + goto out_free; | |
| 853 | + } | |
| 847 | 854 | |
| 848 | 855 | /* map new memory slot into the iommu */ |
| 849 | 856 | if (npages) { |