Il lun 16 giu 2025, 21:00 Annie Li <annie...@oracle.com> ha scritto:
> > My understanding of the qemu document is that it's OK to run one
> > helper per QEMU or even per host, but multiple disks shouldn't share
> > the same socket since it is possible that multiple commands may be
> > sent concurrently.
> >> Maybe QEMU has some internal lock that does the right thing and
> >> serializes requests?
>
Multiple disks can share the socket, the serialization of requests is
handled with a mutex in scsi/pr-manager-helper.c.
> I'll dig the qemu-pr-helper source code. Any thoughts are welcome :)
>
> In libvirt, the socket parameter is configured with '-k' option in
> qemuProcessStartManagedPRDaemon,
>
> if (!(cmd = virCommandNewArgList(prHelperPath,
> "-k", socketPath,
> NULL)))
> and qemu-pr-helper creates socket by the following,
> saddr = (SocketAddress){
> .type = SOCKET_ADDRESS_TYPE_UNIX,
> .u.q_unix.path = socket_path,
> };
> server_ioc = qio_channel_socket_new();
> The 'socket_path' is a global pointer and points to the socketPath
> parameter configured with '-k'(see above in libvirt). Later,
> qemu-pr-helper reads out requests from the socket channel. However, I
> don't see the helper specifically processes PR commands sent
> concurrently by multiple disks. If multiple disks share the same socket,
> there is certainly an issue as what is described in the qemu document.
> I'm wondering if I've missed something here?
>
> Thanks
>
> Annie
>
> > Thanks
> >
> > Annie
> >
> >>
> >> Michal
> >>
> >>>> Due to this limitation above, only one persistent reservation disk is
> >>>> allowed as managed in theory. However, libvirt doesn't throw out any
> >>>> error or warning when the VM is booted up with multiple managed
> >>>> persistent reservation disks. I am wondering if I've missed something
> >>>> here?
> >>>>
> >>>> For unmanaged persistent reservation disks, libvirt doesn't start the
> >>>> pr-helper program for them. It is user's responsibility to start this
> >>>> program with customized socket file per disk, but the complexity
> >>>> increases with numbers of persistent reservation disks, especially in
> >>>> the case of hotplug/hotunplog. Is there any plan to support multiple
> >>>> managed persistent reservation disks with separate pr-helper/socket
> >>>> file?
> >>>>
> >>>> Any suggestions/clarifications are greatly appreciated.
> >>>>
> >>>> Thanks
> >>>>
> >>>> Annie
> >>>>
>
>
