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

[Doug Goldstein <cardoe@xxxxxxxxxx>]

On 11/16/15 1:25 PM, Konrad Rzeszutek Wilk wrote:
> On Mon, Nov 16, 2015 at 08:16:33PM +0100, 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.
> 
> <blinks>I thought Gentoo was all about rebuilding from source and not
> taking binary blobs.

So since SeaBIOS and friends (the blobs) are so sensitive to compilers
and environments and to avoid as much problems for people as possible. I
setup the ebuilds in Gentoo to grab the binary blobs by default and if
the user disabled the binary option it would build from source. The idea
was that Fedora doesn't ship any blobs that can't be rebuilt so I would
follow so the same approach and even use their built blobs. But it
appears to be that there are definitely differences between what QEMU
needs/uses and what upstream ships.

Its pretty common for saying Gentoo is about building from source but
really its about user choice.

That said I haven't been maintaining these for some time now and I've
looked at the state of the way that SeaBIOS and friends are built and I
believe there's an issue and I intend on remedying things soon to avoid
issues like this.

>>
>> 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?
> 
> It may be other options too - like CONFIG_XHCI, or a huge amount of other
> ones.

Yes. There's definitely differences.

>>
>> 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?
> 
> I am not Andrew and can't really speak for him, but I am going to take a 
> leap here and say he will agree with you.
> 


-- 
Doug Goldstein

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