linux-kernel - Re: [PATCH v2 00/12] x86/sev: KEXEC/KDUMP support for SEV-ES guests

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 for Android: free password hash cracker in your pocket

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

Message-ID: <9aa5c10b-56ee-8b26-56d5-870c44e6fbcc@intel.com>
Date:   Mon, 13 Sep 2021 09:21:27 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Joerg Roedel <jroedel@...e.de>
Cc:     Joerg Roedel <joro@...tes.org>, x86@...nel.org,
        Eric Biederman <ebiederm@...ssion.com>,
        kexec@...ts.infradead.org, hpa@...or.com,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Martin Radev <martin.b.radev@...il.com>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v2 00/12] x86/sev: KEXEC/KDUMP support for SEV-ES guests

On 9/13/21 9:14 AM, Joerg Roedel wrote:
> On Mon, Sep 13, 2021 at 09:02:38AM -0700, Dave Hansen wrote:
>> On 9/13/21 8:55 AM, Joerg Roedel wrote:
>>> This does not work under SEV-ES, because the hypervisor has no access
>>> to the vCPU registers and can't make modifications to them. So an
>>> SEV-ES guest needs to reset the vCPU itself and park it using the
>>> AP-reset-hold protocol. Upon wakeup the guest needs to jump to
>>> real-mode and to the reset-vector configured in the AP-Jump-Table.
>> How does this end up looking to an end user that tries to kexec() from a
>> an SEV-ES kernel?  Does it just hang?
> Yes, the kexec will just hang. This patch-set contains code to disable
> the kexec syscalls in situations where it would not work for that
> reason.

Got it.  The end-user-visible symptom just wasn't obvious.  If you
revise these, it might be nice to add that so that folks who cherry-pick
stable patches or update to new stable kernels have an idea what this
might fix.