From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH] KVM: x86: restrict maximal physical address Date: Fri, 25 Nov 2016 17:10:45 +0100 Message-ID: References: <20161125145105.9508-1-rkrcmar@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Return-path: In-Reply-To: <20161125145105.9508-1-rkrcmar@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 25/11/2016 15:51, Radim Krčmář wrote: > The guest could have configured a maximal physical address that exceeds > the host. Prevent that situation as it could easily lead to a bug. > > Signed-off-by: Radim Krčmář > --- > arch/x86/kvm/cpuid.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index 25f0f15fab1a..aed910e9fbed 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -136,7 +136,13 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu) > ((best->eax & 0xff00) >> 8) != 0) > return -EINVAL; > > - /* Update physical-address width */ > + > + /* > + * Update physical-address width. > + * Make sure that it does not exceed hardware capabilities. > + */ > + if (cpuid_query_maxphyaddr(vcpu) > boot_cpu_data.x86_phys_bits) > + return -EINVAL; > vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu); > > kvm_pmu_refresh(vcpu); > Not possible unfortunately, this would break most versions of QEMU that hard-code 40 for MAXPHYADDR. Also, "wider" physical addresses in the guest are actually possible with shadow paging. Paolo