lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Mon, 2 Mar 2020 20:25:31 -0800 From: Jim Mattson <jmattson@...gle.com> To: Sean Christopherson <sean.j.christopherson@...el.com> Cc: Paolo Bonzini <pbonzini@...hat.com>, Vitaly Kuznetsov <vkuznets@...hat.com>, Wanpeng Li <wanpengli@...cent.com>, Joerg Roedel <joro@...tes.org>, kvm list <kvm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, Jan Kiszka <jan.kiszka@...mens.com>, Xiaoyao Li <xiaoyao.li@...el.com> Subject: Re: [PATCH 2/6] KVM: x86: Fix CPUID range check for Centaur and Hypervisor ranges On Mon, Mar 2, 2020 at 7:25 PM Jim Mattson <jmattson@...gle.com> wrote: > > On Mon, Mar 2, 2020 at 11:57 AM Sean Christopherson > <sean.j.christopherson@...el.com> wrote: > > > The bad behavior can be visually confirmed by dumping CPUID output in > > the guest when running Qemu with a stable TSC, as Qemu extends the limit > > of range 0x40000000 to 0x40000010 to advertise VMware's cpuid_freq, > > without defining zeroed entries for 0x40000002 - 0x4000000f. > > I think it could be reasonably argued that this is a userspace bug. > Clearly, when userspace explicitly supplies the results for a leaf, > those results override the default CPUID values for that leaf. But I > haven't seen it documented anywhere that leaves *not* explicitly > supplied by userspace will override the default CPUID values, just > because they happen to appear in some magic range. In fact, the more I think about it, the original change is correct, at least in this regard. Your "fix" introduces undocumented and unfathomable behavior.
Powered by blists - more mailing lists