Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754709AbdLFJ2j (ORCPT ); Wed, 6 Dec 2017 04:28:39 -0500 Received: from mail-pf0-f196.google.com ([209.85.192.196]:44207 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754462AbdLFJ2f (ORCPT ); Wed, 6 Dec 2017 04:28:35 -0500 X-Google-Smtp-Source: AGs4zMbPE24Eh8K8aA42BlP+4AC0/J2240Iv89Phj37g9HFI9gwdxSvXiPq4Nt47H35Z/n0cKucCDQ== From: Wanpeng Li X-Google-Original-From: Wanpeng Li To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Wanpeng Li Subject: [PATCH v2 1/2] KVM: MMU: Fix infinite loop when there is no available mmu page Date: Wed, 6 Dec 2017 01:28:30 -0800 Message-Id: <1512552510-13858-1-git-send-email-wanpeng.li@hotmail.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2741 Lines: 91 From: Wanpeng Li The below test case can cause infinite loop in kvm when ept=0. #include #include #include #include #include #include #include long r[5]; int main() { r[2] = open("/dev/kvm", O_RDONLY); r[3] = ioctl(r[2], KVM_CREATE_VM, 0); r[4] = ioctl(r[3], KVM_CREATE_VCPU, 7); ioctl(r[4], KVM_RUN, 0); } It doesn't setup the memory regions, mmu_alloc_shadow/direct_roots() in kvm return 1 when kvm fails to allocate root page table which can result in beblow infinite loop: vcpu_run() { for (;;) { r = vcpu_enter_guest()::kvm_mmu_reload() returns 1 if (r <= 0) break; if (need_resched()) cond_resched(); } } This patch fixes it by returning -ENOSPC when there is no available kvm mmu page for root page table. Cc: Paolo Bonzini Cc: Radim Krčmář Fixes: 26eeb53cf0f (KVM: MMU: Bail out immediately if there is no available mmu page) Signed-off-by: Wanpeng Li --- v1 -> v2: * cleanup patch description arch/x86/kvm/mmu.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index c9aaa18..89da688 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -3395,7 +3395,7 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu) spin_lock(&vcpu->kvm->mmu_lock); if(make_mmu_pages_available(vcpu) < 0) { spin_unlock(&vcpu->kvm->mmu_lock); - return 1; + return -ENOSPC; } sp = kvm_mmu_get_page(vcpu, 0, 0, vcpu->arch.mmu.shadow_root_level, 1, ACC_ALL); @@ -3410,7 +3410,7 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu) spin_lock(&vcpu->kvm->mmu_lock); if (make_mmu_pages_available(vcpu) < 0) { spin_unlock(&vcpu->kvm->mmu_lock); - return 1; + return -ENOSPC; } sp = kvm_mmu_get_page(vcpu, i << (30 - PAGE_SHIFT), i << 30, PT32_ROOT_LEVEL, 1, ACC_ALL); @@ -3450,7 +3450,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) spin_lock(&vcpu->kvm->mmu_lock); if (make_mmu_pages_available(vcpu) < 0) { spin_unlock(&vcpu->kvm->mmu_lock); - return 1; + return -ENOSPC; } sp = kvm_mmu_get_page(vcpu, root_gfn, 0, vcpu->arch.mmu.shadow_root_level, 0, ACC_ALL); @@ -3487,7 +3487,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) spin_lock(&vcpu->kvm->mmu_lock); if (make_mmu_pages_available(vcpu) < 0) { spin_unlock(&vcpu->kvm->mmu_lock); - return 1; + return -ENOSPC; } sp = kvm_mmu_get_page(vcpu, root_gfn, i << 30, PT32_ROOT_LEVEL, 0, ACC_ALL); -- 2.7.4