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Commit 99894a79 authored by Avi Kivity's avatar Avi Kivity
Browse files

KVM: MMU: Fix off-by-one calculating large page count 



The large page initialization code concludes there are two large pages spanned
by a slot covering 1 (small) page starting at gfn 1.  This is incorrect, and
also results in incorrect write_count initialization in some cases (base = 1,
npages = 513 for example).

Cc: stable@kernel.org
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 09106974

virt/kvm/kvm_main.c

+3 −5
Original line number Diff line number Diff line
@@ -920,6 +920,7 @@ int __kvm_set_memory_region(struct kvm *kvm, 
	int r;

	gfn_t base_gfn;

	unsigned long npages;

	int largepages;

	unsigned long i;

	struct kvm_memory_slot *memslot;

	struct kvm_memory_slot old, new;
@@ -995,11 +996,8 @@ int __kvm_set_memory_region(struct kvm *kvm, 
			new.userspace_addr = 0;

	}

	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++;

		largepages = 1 + (base_gfn + npages - 1) / KVM_PAGES_PER_HPAGE;

		largepages -= base_gfn / KVM_PAGES_PER_HPAGE;



		new.lpage_info = vmalloc(largepages * sizeof(*new.lpage_info));