Re: [xen-unstable test] 64494: regressions - FAIL

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 20/11/15 15:34, Wei Liu wrote:
> On Fri, Nov 20, 2015 at 04:29:04PM +0100, Juergen Gross wrote:
>> On 20/11/15 16:14, Jan Beulich wrote:
>>>>>> On 19.11.15 at 12:47, <JGross@suse.com> wrote:
>>>> On 19/11/15 11:30, Ian Campbell wrote:
>>>>> On Thu, 2015-11-19 at 11:24 +0100, Juergen Gross wrote:
>>>>>> On 18/11/15 15:49, Wei Liu wrote:
>>>>>>> Hi Juergen
>>>>>>>
>>>>>>> Looks like there is something we missed after all.
>>>>>>>
>>>>>>> On Wed, Nov 18, 2015 at 02:31:57PM +0000, osstest service owner wrote:
>>>>>>>> flight 64494 xen-unstable real [real]
>>>>>>>> http://logs.test-lab.xenproject.org/osstest/logs/64494/ 
>>>>>>>>
>>>>>>>> Regressions :-(
>>>>>>>>
>>>>>>>> Tests which did not succeed and are blocking,
>>>>>>>> including tests which could not be run:
>>>>>>>>  test-amd64-amd64-i386-pvgrub 10 guest-start               fail REGR.
>>>>>>>> vs. 64035
>>>>>>> Nov 18 05:11:19.753014 (d2) Bootstrapping...
>>>>>>> Nov 18 05:11:19.769108 (d2) Xen Minimal OS!
>>>>>>> Nov 18 05:11:19.769134 (d2)   start_info: 0xa13000(VA)
>>>>>>> Nov 18 05:11:19.769158 (d2)     nr_pages: 0x20000
>>>>>>> Nov 18 05:11:19.777046 (d2)   shared_inf: 0xca1fc000(MA)
>>>>>>> Nov 18 05:11:19.777072 (d2)      pt_base: 0xa16000(VA)
>>>>>>> Nov 18 05:11:19.785042 (d2) nr_pt_frames: 0xb
>>>>>>> Nov 18 05:11:19.785077 (d2)     mfn_list: 0x993000(VA)
>>>>>>> Nov 18 05:11:19.785108 (d2)    mod_start: 0x0(VA)
>>>>>>> Nov 18 05:11:19.785135 (d2)      mod_len: 0
>>>>>>> Nov 18 05:11:19.793047 (d2)        flags: 0x0
>>>>>>> Nov 18 05:11:19.793077 (d2)     cmd_line: (hd0,0)/boot/grub/menu.lst
>>>>>>> Nov 18 05:11:19.793108 (d2)        stack: 0x972580-0x992580
>>>>>>> Nov 18 05:11:19.801150 (d2) MM: Init
>>>>>>> Nov 18 05:11:19.801181 (d2)       _text: 0x0(VA)
>>>>>>> Nov 18 05:11:19.801197 (d2)      _etext: 0x7b22d(VA)
>>>>>>> Nov 18 05:11:19.809104 (d2)    _erodata: 0xa4000(VA)
>>>>>>> Nov 18 05:11:19.809123 (d2)      _edata: 0xa81a8(VA)
>>>>>>> Nov 18 05:11:19.809138 (d2) stack start: 0x972580(VA)
>>>>>>> Nov 18 05:11:19.817062 (d2)        _end: 0x992b30(VA)
>>>>>>> Nov 18 05:11:19.817099 (d2)   start_pfn: a24
>>>>>>> Nov 18 05:11:19.817125 (d2)     max_pfn: 20000
>>>>>>> Nov 18 05:11:19.825037 (d2) Mapping memory range 0x1000000 - 0x20000000
>>>>>>> Nov 18 05:11:19.825071 (d2) setting 0x0-0xa4000 readonly
>>>>>>> Nov 18 05:11:19.825100 (d2) skipped 1000
>>>>>>> Nov 18 05:11:19.833049 (d2) MM: Initialise page allocator for
>>>>>>> b1c000(b1c000)-20000000(20000000)
>>>>>>> Nov 18 05:11:19.833089 (d2) Page fault at linear address c00008, eip
>>>>>>> 5fc70, regs 0x98ff28, sp b1c000, our_sp 0x98fefc, code 2
>>>>>>> Nov 18 05:11:19.849044 (d2) Page fault in pagetable walk (access to
>>>>>>> invalid memory?).
>>>>>>>
>>>>>>> The pvgrub in used is 32 bit. 64 bit (which I myself tested) seemed to
>>>>>>> be working fine.
>>>>>> Okay, I'm hitting this issue, too. I'll investigate further.
>>>>> Do we want to revert $something in the meantime? If so, what...
>>>>>
>>>> The problem is really located in pvgrub:
>>> One question I have here: Even if this gets fixed in pvgrub (or
>>> mini-os, as it now seems), can we tolerate all existing mini-os
>>> clones now being broken on -unstable (and hence then also
>>> eventually on 4.7)?
>> It would be rather inconvenient if not. The problem is mini-os is
>> relying on an interface which was never meant to be this way. grub-xen
>> is already breaking this interface today, and I think this is okay.
>>
>> Is mini-os shipped independent of Xen in any other product or stand
>> alone?
> Rump kernel has quite a bit of code based on mini-os. I will take care
> of that. That's the only "real" thing based on mini-os that I'm aware
> of.
>
> Given that we split mini-os out just last release, I don't expect there
> are many clones in the wild.

Mirage microkernels use a mini-os base as well.

Having said that, I don't think we should not block this change because
mini-os has been broken in a dumb way for ages.

People using mini-os based things will have to take a "stable update" of
their mini-os to run on Xen 4.7 when it is release.  Linux is treated
exactly the same with bugs like this.

~Andrew