From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: KVM: MMU: make kvm_mmu_available_pages robust against n_used_mmu_pages > n_max_mmu_pages Date: Tue, 12 Mar 2013 22:36:43 -0300 Message-ID: <20130313013642.GA20722@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Gleb Natapov , Paolo Bonzini , Ulrich Obergfell To: kvm Return-path: Received: from mx1.redhat.com ([209.132.183.28]:61427 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755285Ab3CMBmH (ORCPT ); Tue, 12 Mar 2013 21:42:07 -0400 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r2D1g6a1016983 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Tue, 12 Mar 2013 21:42:06 -0400 Content-Disposition: inline Sender: kvm-owner@vger.kernel.org List-ID: As noticed by Ulrich Obergfell , the mmu counters are for beancounting purposes only - so n_used_mmu_pages and n_max_mmu_pages could be relaxed (example: before f0f5933a1626c8df7b), resulting in n_used_mmu_pages > n_max_mmu_pages. Make code robust against n_used_mmu_pages > n_max_mmu_pages. Signed-off-by: Marcelo Tosatti diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index 6987108..3b1ad00 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -57,8 +57,11 @@ int kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *context); static inline unsigned int kvm_mmu_available_pages(struct kvm *kvm) { - return kvm->arch.n_max_mmu_pages - - kvm->arch.n_used_mmu_pages; + if (kvm->arch.n_max_mmu_pages > kvm->arch.n_used_mmu_pages) + return kvm->arch.n_max_mmu_pages - + kvm->arch.n_used_mmu_pages; + + return 0; } static inline void kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu)