lkml.org 
[lkml]   [2011]   [Jul]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [Xen-devel] [PATCH] xen: update machine_to_phys_order on resume
>>> On 13.07.11 at 15:20, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote:
> On Wed, Jul 13, 2011 at 10:12:44AM +0100, Ian Campbell wrote:
>> On Tue, 2011-07-12 at 19:11 +0100, Konrad Rzeszutek Wilk wrote:
>> > On Tue, Jul 12, 2011 at 06:43:42PM +0200, Olaf Hering wrote:
>> > >
>> > > Migration of pv guests fails, the guest crashes on the target host once
> the
>> > > guest is unpaused after transit. It happens when the guest is started on a
>> > > small systen, then migrated from that small system to a large system.
>> > > If the guest is started on a large system, then migrated to a small system
> and
>> > > back to the large system, the migration will be successful.
>> > >
>> > > The issue is that mfn_to_pfn() makes use of machine_to_phys_order, which
>> > > is only configured once early in the boot process. After migration to a
>> > > large host the mfns will exceed the order from the small system and a
>> > > wrong code path is taken.
>> > >
>> > > Calling xen_setup_machphys_mapping() again in the resume path will avoid
>> > > the crash.
>> >
>> > Oh, duh!
>> >
>> > Let me queue that up for 3.0-rc7 unless there are objections?
>>
>> It's not so much an objection to this patch but this issue seems to have
>> been caused by Xen cset 20892:d311d1efc25e which looks to me like a
>> subtle ABI breakage for guests. Perhaps we should introduce a feature
>> flag to indicate that a guest can cope with the m2p changing size over
>> migration like this?
>
> Sounds reasonable to me.. I will wait (I can always submit it during 3.1
> cycle
> and CC stable@kernel.org to backport it to 3.0.1).
>
> Jan, you are the one who came up with the c/s - what's your thought?
> How does your kernel handle the changing size of the M2P - like the patch
> below?

As said in an earlier reply to Ian, I didn't pay attention to the
migration aspects and I'm in favor of introducing a feature flag
to control the behavior.

In the meantime, as an immediate fix, I just sent out a patch to
revert to original behavior for all but Dom0.

Jan



\
 
 \ /
  Last update: 2011-07-15 10:59    [W:0.042 / U:0.156 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site