Re: [libvirt] [PATCH] rng: tighten up domain <controller> schema

On 18/04/13 19:59, Laine Stump wrote: > On 04/18/2013 07:27 AM, Osier Yang wrote: >> On 18/04/13 19:16, Laine Stump wrote: >>> On 04/18/2013 05:41 AM, Martin Kletzander wrote: >>>> On 04/18/2013 11:05 AM, Osier Yang wrote: >>>>> On 18/04/13 17:00, Martin Kletzander wrote: >>>>>> On 04/18/2013 10:54 AM, Osier Yang wrote: >>>>>>> On 18/04/13 16:42, Martin Kletzander wrote: >>>>>>>> On 04/18/2013 06:36 AM, Laine Stump wrote: >>>>>>>>> The rng schema for <controller> had been non-specific about >>>>>>>>> which >>>>>>>>> types of controllers allowed which models, and also allowed the >>>>>>>>> num_queues attribute (since that hasn't been released yet, >>>>>>>>> should we >>>>>>>>> rename it to "numQueues"?) >>>>>>>> Since there's still time (the commit with that is >>>>>>>> v1.0.4-65-gd4bf0a9), I >>>>>>>> think we should rename it ASAP since we are using camelCase for >>>>>>>> all the >>>>>>>> attribute names. >>>>>>>> >>>>>>>> Apart from that, the RNG with this patch is precise according to >>>>>>>> the >>>>>>>> documentation, so ACK. I'll try to send the numQueues patch >>>>>>>> to see >>>>>>>> what >>>>>>>> others think. >>>>>>> I guess you mean multiple queues support for virtio network? >>>>>>> Regardless of which style we will use finally, FYI, >>>>>>> "num_queues" is >>>>>>> used for disk.. Personally I'm fine with either, because we >>>>>>> already >>>>>>> use both across. >>>>>>> >>>>>> Yes, I meant the virtio-scsi num_queues. As we're trying not to >>>>>> use >>>>>> underscores in XML, I hope we can still switch it. I haven't >>>>>> found any >>>>>> other num_queues anywhere in the code. Could you point me to the >>>>>> commit >>>>>> that uses that? I'm sending the previously discussed patch in the >>>>>> meantime. >>>>>> >>>>> Except the virtio-scsi num_queues, there is no other tag for >>>>> multiple >>>>> queue yet, we will need a patch to support multiple queue for the >>>>> network, >>>>> but it's not committed yet. >>>>> >>>>> It's fine to convert it now, 1.0.5 is not released yet. But is it >>>>> deserved to >>>>> do, we already have many tags with underscore, which can't be >>>>> changed >>>>> for back-compat. >>>>> >>>> I believe those attributes [1] were created by mistake, and kept only >>>> because of backward compatibility. I'm trying to be open-minded, >>>> though, so I'm not forcing my patch in, but seeing it just as a >>>> proposal. Others may have different opinions and I'm willing to >>>> discuss >>>> that. My first feeling, though, was that we should try to keep the >>>> same >>>> policy for as many of them as possible. OTOH, I've mistaken the >>>> underscore with a hyphen when I remembered what Daniel told me about >>>> attributes [2]. >>> I had recalled DV saying something about underscores in the names a >>> long >>> time ago, and I recently asked about underscore vs. camelCase, and >>> danpb >>> said the same thing. (Personally I don't have a preference one way or >>> the other, but if we really are trying to avoid them, now is our >>> chance). >> I'm fine with either keeping it or changing num_queues. For long >> term consistence, I agreed with having a consistent naming style >> is nice. >> >>> In the meantime, in other device types, we've tried to keep backend >>> details like this pushed into a <driver> subelement when possible, to >>> avoid polluting the main element (e.g. see the <driver> subelement of >>> <interface>). Is it worth putting this numQueues attribute in a >>> <driver> >>> subelement too? Or am I just playing XML God? >> Not sure if you mean the upcoming numQueues for interface. But for the >> existing num_queues, it's for the virtio-scsi controller, putting it >> in <driver> >> doesn't reflect the purpose. > > But isn't it a backend implementation detail of the specific SCSI > controller? In <interface> and <disk>, information that is specific to a > particular backend (and isn't generally applicable to that type of > device) is in the <driver> subelement. This is the QEMU command line for a virtio-scsi disk: ("-device virtio-scsi-pci" is mapped to virtio-scsi controller in libvirt XML, with num_queues set): <...> -device virtio-scsi-pci,id=scsi0,num_queues=8,bus=pci.0,addr=0x3 \ -usb \ -drive file=/dev/HostVG/QEMUGuest1,if=none,id=drive-scsi0-0-0-0 \ -device scsi-disk,bus=scsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0-0-0-0,id=scsi0-0-0-0 \ </...> And this is the QEMU command line for a virtio disk (with event_idx set): <...> -drive file=/var/lib/libvirt/images/f14.img,if=none,id=drive-virtio-disk0 \ -device virtio-blk-pci,event_idx=on,scsi=off,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virtio-disk0 \ </...> This is the properties the QEMU device "scsi-disk" supports: % ./x86_64-softmmu/qemu-system-x86_64 -device scsi-disk,? scsi-disk.drive=drive scsi-disk.logical_block_size=blocksize scsi-disk.physical_block_size=blocksize scsi-disk.min_io_size=uint16 scsi-disk.opt_io_size=uint32 scsi-disk.bootindex=int32 scsi-disk.discard_granularity=uint32 scsi-disk.ver=string scsi-disk.serial=string scsi-disk.vendor=string scsi-disk.product=string scsi-disk.removable=on/off scsi-disk.dpofua=on/off scsi-disk.wwn=hex64 scsi-disk.channel=uint32 scsi-disk.scsi-id=uint32 scsi-disk.lun=uint32 And the properties "virtio-blk-pci" device supports: % ./x86_64-softmmu/qemu-system-x86_64 -device virtio-blk-pci,? virtio-blk-pci.class=hex32 virtio-blk-pci.ioeventfd=on/off virtio-blk-pci.vectors=uint32 virtio-blk-pci.indirect_desc=on/off virtio-blk-pci.event_idx=on/off virtio-blk-pci.drive=drive virtio-blk-pci.logical_block_size=blocksize virtio-blk-pci.physical_block_size=blocksize virtio-blk-pci.min_io_size=uint16 virtio-blk-pci.opt_io_size=uint32 virtio-blk-pci.bootindex=int32 virtio-blk-pci.discard_granularity=uint32 virtio-blk-pci.cyls=uint32 virtio-blk-pci.heads=uint32 virtio-blk-pci.secs=uint32 virtio-blk-pci.serial=string virtio-blk-pci.config-wce=on/off virtio-blk-pci.scsi=on/off virtio-blk-pci.addr=pci-devfn virtio-blk-pci.romfile=string virtio-blk-pci.rombar=uint32 virtio-blk-pci.multifunction=on/off virtio-blk-pci.command_serr_enable=on/off And the properties "virtio-scsi-pci" device supports: % ./x86_64-softmmu/qemu-system-x86_64 -device virtio-scsi-pci,? virtio-scsi-pci.ioeventfd=on/off virtio-scsi-pci.vectors=uint32 virtio-scsi-pci.indirect_desc=on/off virtio-scsi-pci.event_idx=on/off virtio-scsi-pci.hotplug=on/off virtio-scsi-pci.param_change=on/off virtio-scsi-pci.num_queues=uint32 virtio-scsi-pci.max_sectors=uint32 virtio-scsi-pci.cmd_per_lun=uint32 virtio-scsi-pci.addr=pci-devfn virtio-scsi-pci.romfile=string virtio-scsi-pci.rombar=uint32 virtio-scsi-pci.multifunction=on/off virtio-scsi-pci.command_serr_enable=on/off We can put things like "ioeventfd", "event_idx" in the <driver> subelement, is because of the QEMU device used for disk supports it. But for a virtio-scsi disk, "num_queues" is supported in a separate device "virtio-scsi-pci" instead.. That means, from libvirt p.o.v, things like "ioevent_idx" are for disk, "num_queues" is for the disk controller. Assuming that we put "num_queues" or "numQueues" in <driver>, then we need to find out the controller for disk when building QEMU command line, and check if it's virtio-scsi model, if not, error out, otherwise tell the function to build the controller device string that "num_queues" is specified, and what its value is. Or something similar but reversely (find out the disk associated with the virtio-scsi controller, check if num_queues is specified). This might be not the exact process, but it can show putting "num_queues" in <driver> is just a straight wrong way to go...