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

[Julien Grall <julien.grall@xxxxxxx>]

Hi Jan,

On 12/06/17 16:27, Jan Beulich wrote:
> > > > On 12.06.17 at 17:11, <JBeulich@xxxxxxxx> 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@xxxxxxxxxx>
> > Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> > Tested-by: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> 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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