Re: [Qemu-devel] [PATCH] s390-ccw: Fix alignment for CCW1

[Farhan Ali <alifm@linux.vnet.ibm.com>]

On 08/29/2017 08:04 AM, Cornelia Huck wrote:
> On Mon, 28 Aug 2017 10:28:53 -0400
> Farhan Ali <alifm@linux.vnet.ibm.com> wrote:
>
>> On 08/28/2017 10:19 AM, Halil Pasic wrote:
>>>
>>>
>>> On 08/28/2017 04:15 PM, Farhan Ali wrote:
>>>>
>>>>
>>>> On 08/28/2017 10:05 AM, Cornelia Huck wrote:
>>>>>>>> It's the alignment of the CCW which causes the problem.
>>>>>>>>
>>>>>>>> The exact error message when starting the guest was:
>>>>>>>>
>>>>>>>> ! No virtio device found !
>>>>>>>>
>>>>>>>> Since it worked for SCSI and CDL, and failed for LDL disks on that particular system, we are not really sure what caused the failure.
>>>>>>>> Debugging it further showed the CCW for LDL disks were not aligned at double word boundary.
>>>>> This is really, really odd, as the low-level ccw code is the same for
>>>>> any disk type...
>>>>>
>>>> Exactly!
>>>>
>>>>>>>> Trying the test on a different system with LDL disks worked fine, with the aligned(8) fix.
>>>>>>> Do you happen to have an old s390-ccw.img laying around in the test folder? QEMU might pick up
>>>>>>> this one (e.g. when calling it without libvirt from the command line).
>>>>>>>
>>>>>> I explicitly mention the bios to use with '-bios' option and pick up the
>>>>>> latest bios. Without the aligned fix I see the error and with the fix it
>>>>>> works fine.
>>>>> Wait, so the fix fixes it? Or am I confused now?
>>>>>
>>>>
>>>> It fixes in my system and one other system we tried on. But fails on a system where this issue was first noticed.
>>>
>>> This is very confusing. So you have tried -bios on the system
>>> where the issue was first noticed and the issue still persists
>>> despite of the fixed bios is specified?
>>>
>> Yes.
>>
>> The system where the issue was first noticed, applying the fix for the
>> bios, fixes for:
>>
>> 1) CDL disks
>> 2) SCSI disks
>>
>> But fails for LDL disk.
>>
>> On my system and one other system, the fix works for all the disk types,
>> CDL, SCSI and LDL and fixes the issue.
>
> Are you using different toolchains on the failing and the working
> systems? Does it work when you copy the bios from a working system?
>
> (Clutching at straws here...)
>

So yesterday we realized for the failing system, the bios wasn't being 
built on that system rather it was being built on a different system and 
being copied over to the failing system. :/

Building the bios on the failing system with the fix, resolves the issue 
and we did not see anymore failures.
So I think I can safely say this patch fixes the alignment problem.