KVM: MMU: large page support
Create large pages mappings if the guest PTE's are marked as such and
the underlying memory is hugetlbfs backed. If the largepage contains
write-protected pages, a large pte is not used.
Gives a consistent 2% improvement for data copies on ram mounted
filesystem, without NPT/EPT.
Anthony measures a 4% improvement on 4-way kernbench, with NPT.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index c41eb57..31db9b4 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -212,9 +212,13 @@
if (!dont || free->dirty_bitmap != dont->dirty_bitmap)
vfree(free->dirty_bitmap);
+ if (!dont || free->lpage_info != dont->lpage_info)
+ vfree(free->lpage_info);
+
free->npages = 0;
free->dirty_bitmap = NULL;
free->rmap = NULL;
+ free->lpage_info = NULL;
}
void kvm_free_physmem(struct kvm *kvm)
@@ -324,6 +328,25 @@
new.user_alloc = user_alloc;
new.userspace_addr = mem->userspace_addr;
}
+ if (npages && !new.lpage_info) {
+ int largepages = npages / KVM_PAGES_PER_HPAGE;
+ if (npages % KVM_PAGES_PER_HPAGE)
+ largepages++;
+ if (base_gfn % KVM_PAGES_PER_HPAGE)
+ largepages++;
+
+ new.lpage_info = vmalloc(largepages * sizeof(*new.lpage_info));
+
+ if (!new.lpage_info)
+ goto out_free;
+
+ memset(new.lpage_info, 0, largepages * sizeof(*new.lpage_info));
+
+ if (base_gfn % KVM_PAGES_PER_HPAGE)
+ new.lpage_info[0].write_count = 1;
+ if ((base_gfn+npages) % KVM_PAGES_PER_HPAGE)
+ new.lpage_info[largepages-1].write_count = 1;
+ }
/* Allocate page dirty bitmap if needed */
if ((new.flags & KVM_MEM_LOG_DIRTY_PAGES) && !new.dirty_bitmap) {
@@ -467,7 +490,7 @@
}
EXPORT_SYMBOL_GPL(kvm_is_visible_gfn);
-static unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
+unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
{
struct kvm_memory_slot *slot;