linux-kernel - Re: [PATCH v2 01/12] kexec: Allow architecture code to opt-out at runtime

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Message-ID: <87pmrjbmy9.fsf@disp2133>
Date:   Mon, 01 Nov 2021 16:11:42 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Borislav Petkov <bp@...en8.de>
Cc:     Joerg Roedel <joro@...tes.org>, x86@...nel.org,
        kexec@...ts.infradead.org, Joerg Roedel <jroedel@...e.de>,
        stable@...r.kernel.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 01/12] kexec: Allow architecture code to opt-out at runtime

Borislav Petkov <bp@...en8.de> writes:

> On Mon, Sep 13, 2021 at 05:55:52PM +0200, Joerg Roedel wrote:
>> From: Joerg Roedel <jroedel@...e.de>
>> 
>> Allow a runtime opt-out of kexec support for architecture code in case
>> the kernel is running in an environment where kexec is not properly
>> supported yet.
>> 
>> This will be used on x86 when the kernel is running as an SEV-ES
>> guest. SEV-ES guests need special handling for kexec to hand over all
>> CPUs to the new kernel. This requires special hypervisor support and
>> handling code in the guest which is not yet implemented.
>> 
>> Cc: stable@...r.kernel.org # v5.10+
>> Signed-off-by: Joerg Roedel <jroedel@...e.de>
>> ---
>>  include/linux/kexec.h |  1 +
>>  kernel/kexec.c        | 14 ++++++++++++++
>>  kernel/kexec_file.c   |  9 +++++++++
>>  3 files changed, 24 insertions(+)
>
> I guess I can take this through the tip tree along with the next one.

I seem to remember the consensus when this was reviewed that it was
unnecessary and there is already support for doing something like
this at a more fine grained level so we don't need a new kexec hook.

Eric