KVM: MMU: Fix off-by-one calculating large page count (99894a79) · Commits · 戴 / test

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:

Avi Kivity <avi@redhat.com>

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));

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