RBD volume not made available to Xen virtual guest on openSUSE 15.2 (with libvirt 6.0.0)

[Marcel Juffermans]

Further to this, the error may be coming from QEMU, but the guests work 
fine when started using KVM (+ libvirt + QEMU) instead of Xen (+ libvirt 
+ QEMU). So is it possible the problem is in libvirt, or rather, in the 
interaction between libvirt, Xen and QEMU?

Marcel
On 27/10/20 9:18 am, Marcel Juffermans wrote:
> It's QEMU 4.2.1-lp152.9.6.1.
>
> I've tried updating it from the Open Build Service repos but there's 
> too many version conflicts.
>
> Marcel
> On 26/10/20 9:02 pm, Ján Tomko wrote:
>> On a Friday in 2020, Marcel Juffermans wrote:
>>> Hi there,
>>>
>>> Since upgrading to openSUSE 15.2 (which includes libvirt 6.0.0) the 
>>> virtual guests don't get their RBD disks made available to them. On 
>>> openSUSE 15.1 (which includes libvirt 5.1.0) that worked fine. The 
>>> XML is as follows:
>>>
>>
>> [...]
>>
>>> I tried to strace libvirtd. The results are as follows:
>>>
>>> On openSUSE 15.2 with libvirt 6.0.0 (not working), we see this:
>>>
>>> 1682  openat(AT_FDCWD, 
>>> "rbd:guests/mytwotel-a:id=libvirt:key=AQCAUpBbrcaiFxAA1sztXPbkdW1L54i99oUpyA==:auth_supported=cephx\\;none", 
>>> O_RDWR|O_CLOEXEC) = -1 ENOENT (No such file or directory)
>>> 1682  rt_sigprocmask(SIG_BLOCK, NULL, [BUS USR1 ALRM IO], 8) = 0
>>> 1682  mmap(NULL, 1052672, PROT_READ|PROT_WRITE, 
>>> MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f538aefd000
>>> 1682  mprotect(0x7f538aefd000, 4096, PROT_NONE <unfinished ...>
>>> 1682  <... mprotect resumed>)           = 0
>>> 1682  rt_sigprocmask(SIG_SETMASK, [BUS USR1 ALRM IO], [BUS USR1 ALRM 
>>> IO], 8) = 0
>>> 1682  rt_sigprocmask(SIG_BLOCK, NULL, [BUS USR1 ALRM IO], 8) = 0
>>> 1682  mmap(NULL, 1052672, PROT_READ|PROT_WRITE, 
>>> MAP_PRIVATE|MAP_ANONYMOUS, -1, 0 <unfinished ...>
>>> 1682  <... mmap resumed>)               = 0x7f538adfc000
>>> 1682  mprotect(0x7f538adfc000, 4096, PROT_NONE <unfinished ...>
>>> 1682  <... mprotect resumed>)           = 0
>>> 1682  rt_sigprocmask(SIG_SETMASK, [BUS USR1 ALRM IO], <unfinished ...>
>>> 1682  <... rt_sigprocmask resumed>[BUS USR1 ALRM IO], 8) = 0
>>> 1682  write(2, "qemu-system-i386: failed to crea"..., 232 
>>> <unfinished ...>
>>> ...
>>>
>>> On the other hand, on openSUSE 15.1 with libvirt 5.1.0 (working), we 
>>> see this:
>>>
>>> 16267 openat(AT_FDCWD, 
>>> "rbd:guests/mytwotel-a:id=libvirt:key=AQCAUpBbrcaiFxAA1sztXPbkdW1L54i99oUpyA==:auth_supported=cephx\\;none", 
>>> O_RDONLY|O_NONBLOCK|O_CLOEXEC) = -1 ENOENT (No such file or directory)
>>> 16267 
>>> stat("rbd:guests/mytwotel-a:id=libvirt:key=AQCAUpBbrcaiFxAA1sztXPbkdW1L54i99oUpyA==:auth_supported=cephx\\;none", 
>>> 0x7fff83e2e2b0) = -1 ENOENT (No such file or directory)
>>> 16267 access("/usr/lib64/qemu/block-rbd.so", F_OK) = 0
>>> 16267 stat("/usr/lib64/qemu/block-rbd.so", {st_mode=S_IFREG|0644, 
>>> st_size=27448, ...}) = 0
>>> 16267 openat(AT_FDCWD, "/usr/lib64/qemu/block-rbd.so", 
>>> O_RDONLY|O_CLOEXEC) = 60
>>> 16267 read(60, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0 
>>> &\0\0\0\0\0\0"..., 832) = 832
>>> 16267 fstat(60, {st_mode=S_IFREG|0644, st_size=27448, ...}) = 0
>>> 16267 mmap(NULL, 2122672, PROT_READ|PROT_EXEC, 
>>> MAP_PRIVATE|MAP_DENYWRITE, 60, 0) = 0x7f8e6030f000
>>> 16267 mprotect(0x7f8e60315000, 2093056, PROT_NONE) = 0
>>> 16267 mmap(0x7f8e60514000, 8192, PROT_READ|PROT_WRITE, 
>>> MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 60, 0x5000) = 0x7f8e60514000
>>> 16267 close(60)                         = 0
>>> ...
>>>
>>> Note that the latter opens "/usr/lib64/qemu/block-rbd.so". That 
>>> library *does* exist on openSUSE 15.2 but it doesn't seem to be used.
>>>
>>
>> The error message comes from QEMU, what QEMU version are you using?
>>
>> Jano
>>
>>> I've tried to update libvirt to a newer version using the Open Build 
>>> Service repos, but then ran into so many conflicting versions that I 
>>> gave up.
>>>
>>> At this point I'm stuck. Does anyone have an idea I can try?
>>>
>>> Many thanks,
>>>
>>> Marcel
>>>
>>>
>>>
>>>
>>>
>>>
>