Re: [PATCH] x86/boot: re-arrange how/when we do disk I/O

[Julien Grall <julien.grall@arm.com>]

Hi Jan,

On 12/06/17 16:27, Jan Beulich wrote:
>>>> On 12.06.17 at 17:11, <JBeulich@suse.com> wrote:
>> We place the trampoline no lower than at 256k, so we have ample space
>> to read the MBRs of BIOS disks into an aligned buffer right below the
>> trampoline (not doing so has been found to be a problem on a buggy BIOS
>> coming with a Skull Canyon NUC). To facilitate that move MBR reading
>> past EDD info retrieval.
>>
>> Also add a wrap check to the EDD info retrieval loop, to match that in
>> the MBR reading one.
>>
>> Reported-by: Paul Durrant <Paul.Durrant@citrix.com>
>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>> Tested-by: Paul Durrant <Paul.Durrant@citrix.com>
>
> As to 4.9 inclusion, I think I should have mentioned right away
> that such a change of course isn't without risk: We're trying to
> work around a BIOS bug by relying on other information
> coming from the BIOS being correct / usable. Obviously there is
> the risk that this regresses with some other BIOS having a bug
> elsewhere.
>
> I'm therefore leaning towards suggesting to take this change
> only for master right now, and consider pulling it into the 4.9
> branch in a couple of weeks time, when the patch has seen at
> least a little more testing on a wider set of systems.

I agree on your conclusion. I would suggest to add a release note if it 
is not backported before the release.

I will keep track of this.

Cheers,

-- 
Julien Grall

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