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From:   ebiederm@xmission.com (Eric W. Biederman)
To:     Borislav Petkov <bp@alien8.de>
Cc:     Joerg Roedel <joro@8bytes.org>, x86@kernel.org,
        kexec@lists.infradead.org, Joerg Roedel <jroedel@suse.de>,
        stable@vger.kernel.org, hpa@zytor.com,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Jiri Slaby <jslaby@suse.cz>,
        Dan Williams <dan.j.williams@intel.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Juergen Gross <jgross@suse.com>,
        Kees Cook <keescook@chromium.org>,
        David Rientjes <rientjes@google.com>,
        Cfir Cohen <cfir@google.com>,
        Erdem Aktas <erdemaktas@google.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Mike Stunes <mstunes@vmware.com>,
        Sean Christopherson <seanjc@google.com>,
        Martin Radev <martin.b.radev@gmail.com>,
        Arvind Sankar <nivedita@alum.mit.edu>,
        linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, virtualization@lists.linux-foundation.org
References: <20210913155603.28383-1-joro@8bytes.org>
        <20210913155603.28383-2-joro@8bytes.org> <YYARccITlowHABg1@zn.tnic>
Date:   Mon, 01 Nov 2021 16:11:42 -0500
In-Reply-To: <YYARccITlowHABg1@zn.tnic> (Borislav Petkov's message of "Mon, 1
        Nov 2021 17:10:25 +0100")
Message-ID: <87pmrjbmy9.fsf@disp2133>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux)
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Subject: Re: [PATCH v2 01/12] kexec: Allow architecture code to opt-out at runtime
Precedence: bulk

Borislav Petkov <bp@alien8.de> writes:

> On Mon, Sep 13, 2021 at 05:55:52PM +0200, Joerg Roedel wrote:
>> From: Joerg Roedel <jroedel@suse.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@vger.kernel.org # v5.10+
>> Signed-off-by: Joerg Roedel <jroedel@suse.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