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Subject: Re: [PATCH v5 0/3] x86: make rsdp address accessible via boot params
To:     Ingo Molnar <mingo@kernel.org>
Cc:     linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org,
        x86@kernel.org, linux-doc@vger.kernel.org, tglx@linutronix.de,
        mingo@redhat.com, bp@alien8.de, hpa@zytor.com, corbet@lwn.net,
        boris.ostrovsky@oracle.com,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Kees Cook <keescook@chromium.org>
References: <20181010061456.22238-1-jgross@suse.com>
 <20181010062352.GC37224@gmail.com>
 <12afa65a-9e07-bb2c-5621-85074ea37135@suse.com>
 <20181010071918.GA103159@gmail.com>
From:   Juergen Gross <jgross@suse.com>
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Date:   Wed, 10 Oct 2018 09:28:15 +0200
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On 10/10/2018 09:19, Ingo Molnar wrote:
> 
> * Juergen Gross <jgross@suse.com> wrote:
> 
>> You can just dive into the discussion we had back in February:
> 
> That was half a year and a thousand commits ago! ;-)

Yes. :-)

> 
>> https://lore.kernel.org/lkml/20180213163244.j2zuxyhs4kbfhwgj@gmail.com/
>>
>> The scheme I have used in V5 of the series is the one you agreed to use
>> back then.
>>
>> A quick summary of the problem you mentioned:
>>
>> There are some downstream variants of grub2 with a patch breaking the
>> boot protocol by writing garbage past the end of setup_header. Adding
>> a new field at the end of setup_header (here: rsdp_address) resulted in
>> those grub2 variants clobbering the preset value of 0.
>>
>> The solution is to let grub2 report back the used boot protocol version
>> with setting a flag "I am reporting back my version". The kernel now is
>> capable to know which fields of setup_header are known to grub2 and can
>> act accordingly.
>>
>> The related grub2 patch series is under review right now.
> 
> Ok, that's reassuring - that's all the context I needed.
> 
> Would it help grub2 review+integration if we applied this to -tip and staged
> it there until the Grub patches are accepted, or can I consider those changes
> as grub2 upstream accepted?

Applying to -tip would really be great! I can send you a note when the
grub series has been accepted. The grub maintainer has already sent me
a note he will be looking at the patches soon.

> I'd like to help make it happen, let me know what the best route is.

I appreciate that a lot!


Thanks,

Juergen