From: Paul Durrant <Paul.Durrant@citrix.com>
To: 'Jan Beulich' <JBeulich@suse.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: Fri, 9 Jun 2017 15:47:27 +0000 [thread overview]
Message-ID: <c394e22eb2d24f379e34b402b69c3bb6@AMSPEX02CL03.citrite.net> (raw)
In-Reply-To: <593ADDBC020000780016171F@prv-mh.provo.novell.com>
> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@suse.com]
> Sent: 09 June 2017 16:41
> To: Paul Durrant <Paul.Durrant@citrix.com>
> Cc: Julien Grall (julien.grall@arm.com) <julien.grall@arm.com>; Andrew
> Cooper <Andrew.Cooper3@citrix.com>; xen-devel(xen-
> devel@lists.xenproject.org) <xen-devel@lists.xenproject.org>; 'Boris
> Ostrovsky' <boris.ostrovsky@oracle.com>; Juergen Gross
> <jgross@suse.com>
> Subject: RE: [Xen-devel] debian stretch dom0 + xen 4.9 fails to boot
>
> >>> On 09.06.17 at 17:14, <Paul.Durrant@citrix.com> wrote:
> > I've characterised the issue some more and it appears to be an overflow
> > inside the int13 handler if es:bx is less than 512 bytes below a 4k boundary.
> > I modified the code to use a hardcoded segment, which I set at 0x6000, and
> > all values of bx up to 0xe00 resulted in a good MBR signature. Values above
> > 0xe00 but below 0xe20 resulted in the buffer not being identified as a valid
> > MBR (I guess because the 0xAA55 fell off) and values of bx above 0xe20
> > resulted in either a hang (sometimes with a black screen) or a reboot.
> > This led me to believe that backing out all my debug code and adding a
> > '.align 512' just before the definition of boot_edd_info should result in a
> > successful boot. Alas this appears not to be the case... I seem to need at
> > least 2k alignment. I wonder whether it may be more robust to go for 4k
> > alignment though.
>
> At least until we've seen (and merged) Jürgen's further trampoline
> adjustments, we need to be careful with growing its overall size.
> Memory below 1Mb is known to be scarce specifically on some EFI
> systems, and we're currently still allocating space for all of the
> trampoline instead of just its permanent part. Even on non-EFI
> systems I'd prefer the trampoline to remain as small as possible.
>
> With what you say about the requirements this buggy BIOS has
> I wonder whether we couldn't help ourselves by doing I/O to
> other than boot_edd_info. Especially if we did the EDD stuff last
> (rather than before video), a good portion of the boot time only
> trampoline space will no longer be needed.
I think that would be sensible, but I was looking for the simplest fix/workaround possible for 4.9 and setting the alignment seems to it.
>
> Otoh I wonder where a system this buggy shouldn't be declared
> unusable (until a suitable BIOS update becomes available). Did
> you check what constraints Linux places on the buffer used for
> I/O? IOW can you judge whether bare metal Linux just happens
> to work (just like older Xen did), or has been fixed to cope with
> such a situation?
>
I'll go have a look and the linux edd code. I'm also trying a BIOS update (which is proving to be trickier than I thought as it seems to have killed networking in some weird way).
Paul
> Jan
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next prev parent reply other threads:[~2017-06-09 15:47 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-06 14:32 debian stretch dom0 + xen 4.9 fails to boot Paul Durrant
2017-06-06 15:11 ` Jan Beulich
2017-06-06 15:51 ` Paul Durrant
2017-06-06 16:28 ` Paul Durrant
2017-06-06 17:00 ` Boris Ostrovsky
2017-06-07 8:07 ` Jan Beulich
2017-06-07 8:09 ` Paul Durrant
2017-06-07 8:19 ` Paul Durrant
2017-06-07 14:05 ` Boris Ostrovsky
2017-06-07 8:07 ` Paul Durrant
2017-06-07 8:27 ` Jan Beulich
[not found] ` <5937D4FF02000078001602F6@suse.com>
2017-06-07 9:03 ` Juergen Gross
2017-06-07 9:05 ` Paul Durrant
2017-06-07 9:09 ` Andrew Cooper
2017-06-07 10:36 ` Paul Durrant
2017-06-07 11:06 ` Paul Durrant
2017-06-07 11:57 ` Juergen Gross
2017-06-07 12:02 ` Paul Durrant
2017-06-07 12:13 ` Juergen Gross
2017-06-07 12:19 ` Jan Beulich
2017-06-07 12:26 ` Paul Durrant
2017-06-07 12:34 ` Jan Beulich
2017-06-07 11:50 ` Jan Beulich
2017-06-07 11:55 ` Paul Durrant
2017-06-07 12:00 ` Jan Beulich
2017-06-07 12:46 ` Paul Durrant
2017-06-07 12:55 ` Jan Beulich
2017-06-07 15:06 ` Paul Durrant
2017-06-07 15:33 ` Jan Beulich
2017-06-07 15:40 ` Paul Durrant
2017-06-07 15:52 ` Jan Beulich
2017-06-08 12:42 ` Paul Durrant
2017-06-08 12:46 ` Juergen Gross
2017-06-08 13:18 ` Jan Beulich
2017-06-08 13:24 ` Paul Durrant
2017-06-09 12:19 ` Paul Durrant
2017-06-09 13:05 ` Jan Beulich
2017-06-09 13:52 ` Boris Ostrovsky
2017-06-09 15:14 ` Paul Durrant
2017-06-09 15:41 ` Jan Beulich
2017-06-09 15:47 ` Paul Durrant [this message]
2017-06-09 15:58 ` Jan Beulich
2017-06-12 8:14 ` Paul Durrant
2017-06-12 10:40 ` Jan Beulich
2017-06-12 10:44 ` Paul Durrant
2017-06-12 10:53 ` Paul Durrant
2017-06-12 11:12 ` Jan Beulich
2017-06-12 12:05 ` Paul Durrant
2017-06-12 12:25 ` Paul Durrant
2017-06-12 13:54 ` Jan Beulich
2017-06-12 14:28 ` Paul Durrant
2017-06-12 14:43 ` Paul Durrant
2017-06-12 15:03 ` Paul Durrant
2017-06-12 15:07 ` Jan Beulich
2017-06-12 15:21 ` Paul Durrant
2017-06-06 17:40 ` Julien Grall
2017-06-07 8:05 ` Paul Durrant
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