linux-kernel - Re: [PATCH 17/15] KVM: X86: Ensure pae_root to be reconstructed for shadow paging if the guest PDPTEs is changed

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

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Ybd63U3f9kXrMVEs@google.com>
Date:   Mon, 13 Dec 2021 16:54:53 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Maxim Levitsky <mlevitsk@...hat.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Lai Jiangshan <laijs@...ux.alibaba.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Xiao Guangrong <guangrong.xiao@...ux.intel.com>
Subject: Re: [PATCH 17/15] KVM: X86: Ensure pae_root to be reconstructed for
 shadow paging if the guest PDPTEs is changed

On Sat, Dec 11, 2021, Paolo Bonzini wrote:
> On 12/11/21 07:56, Maxim Levitsky wrote:
> > > This apparently wasn't validated against a simple use case, let
> > > alone against things like migration with nested VMs, multliple L2s,
> > > etc...
> > 
> > I did validate the *SREGS2* against all the cases I could (like
> > migration, EPT/NPT disabled/etc. I even started testing SMM to see
> > how it affects PDPTRs, and patched seabios to use PAE paging. I still
> > could have missed something.
> 
> Don't worry, I think Sean was talking about patch 16 and specifically
> digging at me (who deserved it completely).

Yes, patch 16.  My goal wasn't to dig at anyone, I just wanted to dramatically
emphasize how ridiculousy fragile and complex the PDPTR crud is due to the number
of edge cases.