Re: debian stretch dom0 + xen 4.9 fails to boot

From: "Jan Beulich" <JBeulich@suse.com>
To: Paul Durrant <Paul.Durrant@citrix.com>
Cc: Juergen Gross <jgross@suse.com>,
	Andrew Cooper <Andrew.Cooper3@citrix.com>,
	"Julien Grall (julien.grall@arm.com)" <julien.grall@arm.com>,
	'Boris Ostrovsky' <boris.ostrovsky@oracle.com>,
	"xen-devel(xen-devel@lists.xenproject.org)"
	<xen-devel@lists.xenproject.org>
Subject: Re: debian stretch dom0 + xen 4.9 fails to boot
Date: Mon, 12 Jun 2017 05:12:11 -0600	[thread overview]
Message-ID: <593E932B0200007800161E80@prv-mh.provo.novell.com> (raw)
In-Reply-To: <7383a46c90814caba440ca41ccde6f88@AMSPEX02CL03.citrite.net>

>>> On 12.06.17 at 12:53, <Paul.Durrant@citrix.com> wrote:
>>  -----Original Message-----
> [snip]
>> > >
>> > > What do you think it best to do for Xen 4.9? Hardcoding a 4k alignment is
>> > > clearly easy and would work around this BIOS issue but, as you say, it
>> does
>> > > grow the image. Reverting Juergen's patch also works round the issue,
>> but
>> > > that is more by luck. Re-working the code is preferable, but I guess it's
>> too
>> > > late to introduce such code-churn in 4.9.
>> >
>> > Reverting Jürgen's code is out of question with all the information
>> > you've gathered by now. I think re-working the EDD code slightly
>> > is the best option. Would you mind giving the attached patch a
>> > try? This still slightly grows the trampoline due to a few more
>> > instructions being needed, but should still be far better than
>> > embedding a whole 4k buffer (and then later finding a BIOS/disk
>> > combination which wants even more). Note that I've left a tiny
>> > bit of debugging code in there.
>> >
>> 
>> Sure, I'll give that a go now.
>> 
> 
> That worked fine:
> 
> (XEN) MBR[80] @ 85e0 (86000)

But that's contrary to your earlier findings: Didn't you say simply
avoiding a 4k-boundary wasn't enough? And it certainly tells us
that this isn't a 4k drive (or at least the BIOS doesn't surface 4k
sectors) - I was really expecting a larger gap between the two
logged values.

> so you can add my Tested-by to that.

I.e. I'm not sure about this, as I'm still uncertain whether some
corruption didn't again occur. Of course APs coming up properly
would already be a relatively good sign (as now the permanent
part of the trampoline would be the predestined area for
corruption to occur in).

Jan

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