Re: [Xen-devel] XSAVE/XRSTOR crash resurgence in 4.3

[Ben Guthro <ben.guthro@xxxxxxxxx>]

On Mon, Jul 8, 2013 at 10:47 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>> On 08.07.13 at 16:42, Ben Guthro <ben.guthro@xxxxxxxxx> wrote:
>> On Jul 8, 2013, at 10:41 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>
>>>>>> On 08.07.13 at 16:31, Ben Guthro <ben@xxxxxxxxxx> wrote:
>>>> On Mon, Jul 8, 2013 at 10:24 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>>>>>> On 08.07.13 at 16:13, Ben Guthro <ben@xxxxxxxxxx> wrote:
>>>>>> On Fri, Jul 5, 2013 at 8:58 AM, Ben Guthro <ben.guthro@xxxxxxxxx> wrote:
>>>>>>> On Jul 5, 2013, at 8:15 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>>>>>
>>>>>>>>>>> On 05.07.13 at 14:10, Ben Guthro <ben.guthro@xxxxxxxxx> wrote:
>>>>>>>>> Since I am not in the office today, nor near a machine that I can
>>>>>>>>> access this, I asked someone else to apply and check in this patch, in
>>>>>>>>> the hope that we could get some useful debug info from the weekend
>>>>>>>>> test run.
>>>>>>>>>
>>>>>>>>> However, when he went to test booting a VM with this patch, the host
>>>>>>>>> machine rebooted - presumably a Xen crash.
>>>>>>>>
>>>>>>>> Oops - it's just printing stuff, so I can't immediately see how that
>>>>>>>> would happen. But perhaps a trivial oversight of mine...
>>>>>>
>>>>>> Here's the crash with this patch
>>>>>> I'm continuing to look at it, but if something jumps out at you,
>>>>>> please let me know.
>>>>>
>>>>> Quite obvious: hvm_guest_x86_mode() has this assertion. Yet
>>>>> the original, supposedly working patch had a use of this too iirc.
>>>>
>>>> It did...which is worrying.
>>>>
>>>> One difference here, is that 4.2 is running in debug=n mode, where 4.3
>>>> is debug=y
>>>>
>>>> iirc, asserts are disabled on debug=n builds.
>>>
>>> Oh, right. And in the context here the assertion triggering is
>>> apparently wrong anyway. For the purpose of debugging the
>>> issue at hand, I think it is safe to comment it out.
>>
>> Ok, I'll do that, thanks
>
> Or, perhaps better, replace the call in the patch with one to
> hvmfuncs.guest_x86_mode(). That's what I have done in my
> copy of the patch just now (in case we need a second rev at
> some point).
>

Good idea. I'm testing a patch now, and will get it into tonight's test run.
Hopefully I'll have some data to share tomorrow morning.

Ben

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