Re: [Xen-devel] HVM domains crash after upgrade from XEN 4.5.1 to 4.5.2

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 16/11/2015 19:16, Atom2 wrote:
>
>
> Am 16.11.15 um 16:31 schrieb Konrad Rzeszutek Wilk:
>>>>> Your analysis was absolutely spot on. After re-thinking this for a
>>>>> moment, I thought going down that route first would make a lot of
>>>>> sense
>>>>> as PV guests still do work and one of the differences to HVM domUs is
>>>>> that the former do _not_ require SeaBIOS. Looking at my log files of
>>>>> installed packages confirmed an upgrade from SeaBIOS 1.7.5 to
>>>>> 1.8.2 in
>>>>> the relevant timeframe which obviously had not made it to the
>>>>> hvmloader
>>>>> of xen-4.5.1 as I did not re-compile xen after the upgrade of
>>>>> SeaBIOS.
>>>>>
>>>>> So I re-compiled xen-4.5.1 (obviously now using the installed SeaBIOS
>>>>> 1.8.2) and the same error as with xen-4.5.2 popped up - and that
>>>>> seemed
>>>>> to strongly indicate that there indeed might be an issue with
>>>>> SeaBIOS as
>>>>> this probably was the only variable that had changed from the
>>>>> original
>>>>> install of xen-4.5.1.
>> I recall seeing this way back in Fedora 20 days. I narrowed it down the
>> SeaBIOS version that was a standalone package to not have CONFIG_XEN.
>>
>> Having that fixed in the SeaBIOS package fixed it.
> Hi Konrad, Doug, Andrew (specifically added to this part of the thread)!
> Konrad, you might have found an interesting point. I did have a look
> at the ebuild for the failing version and in there I found the
> following comment:
> ====== comment from ebuild =======
>     # Upstream hasn't released a new binary.  We snipe ours from
> Fedora for now.
>     # http://code.coreboot.org/p/seabios/downloads/get/bios.bin-${PV}.gz
> ====== end comment from ebuild =======
> which might in fact underline that there might be an issue similar to
> what you described above.
>
> What is also pretty interesting is the fact that the old (working)
> SeaBIOS version 1.7.5 installed as "bios.bin" under /usr/share/seabios
> is actually 262.144 bytes in size whereas the new (invalid) SeaBIOS
> 1.8.2 installed in the same location is only half as big: 131.072 bytes.
>
> I checked at the download site and the 1.8.2 binary version is indeed
> not available from http://code.coreboot.org/p/seabios/downloads/. But
> both the binary versions for 1.7.5 and 1.8.0 are available and both
> are acutually 262.144 bytes in size, so I'd be very surprised if the
> 1.8.2 version is really only half that size. By the way, the old
> working version (according to the ebuild) was directly downloaded from
> the above url and also shows an identical SHA1 digest to that version
> available for download there.
>
> To me this looks as if something is really wrong here. If anybody of
> you has access to a 1.8.2 version, could you please confirm whether
> there's really that big a size difference between the 1.7.5 and the
> 1.8.2 versions? Or is that difference probably attributable to the
> missing CONFIG_XEN option?
>
> Andrew: I havent't gotten around to run the debug version of the
> hypervisor again, but if the current suspicion turns out to be true,
> there's probably not much value in that anyways. Would you agree?

Sadly not.

I accept that this issue is possibly fixed in newer SeaBIOS by working
around the issue.

However, I stand by my original point.  *There is no way the guest
should be able to get into this situation in the first place*, and its
implication of *there is a genuine hypervisor bug which we should track
down*, irrespective of whether the issue has been worked around elsehow.

~Andrew

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