Messages in this thread Patch in this message | | | Date | Fri, 04 Sep 2009 17:14:06 -0700 | From | Greg KH <> | Subject | [patch 31/71] KVM: MMU: handle n_free_mmu_pages > n_alloc_mmu_pages in kvm_mmu_change_mmu_pages |
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2.6.30-stable review patch. If anyone has any objections, please let us know.
------------------ From: Marcelo Tosatti <mtosatti@redhat.com>
(cherry picked from commit 025dbbf36a7680bffe54d9dcbf0a8bc01a7cbd10)
kvm_mmu_change_mmu_pages mishandles the case where n_alloc_mmu_pages is smaller then n_free_mmu_pages, by not checking if the result of the subtraction is negative.
Its a valid condition which can happen if a large number of pages has been recently freed.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> --- arch/x86/kvm/mmu.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-)
--- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -1417,24 +1417,25 @@ static int kvm_mmu_zap_page(struct kvm * */ void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned int kvm_nr_mmu_pages) { + int used_pages; + + used_pages = kvm->arch.n_alloc_mmu_pages - kvm->arch.n_free_mmu_pages; + used_pages = max(0, used_pages); + /* * If we set the number of mmu pages to be smaller be than the * number of actived pages , we must to free some mmu pages before we * change the value */ - if ((kvm->arch.n_alloc_mmu_pages - kvm->arch.n_free_mmu_pages) > - kvm_nr_mmu_pages) { - int n_used_mmu_pages = kvm->arch.n_alloc_mmu_pages - - kvm->arch.n_free_mmu_pages; - - while (n_used_mmu_pages > kvm_nr_mmu_pages) { + if (used_pages > kvm_nr_mmu_pages) { + while (used_pages > kvm_nr_mmu_pages) { struct kvm_mmu_page *page; page = container_of(kvm->arch.active_mmu_pages.prev, struct kvm_mmu_page, link); kvm_mmu_zap_page(kvm, page); - n_used_mmu_pages--; + used_pages--; } kvm->arch.n_free_mmu_pages = 0; }
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