Re: [libvirt] [PATCH 4/4] qemu: Allow use of iothreads for disk definitions

On Mon, Aug 25, 2014 at 08:38:09PM -0400, John Ferlan wrote: > diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c > index 287a3f3..740b6ec 100644 > --- a/src/qemu/qemu_command.c > +++ b/src/qemu/qemu_command.c > @@ -3862,6 +3862,9 @@ qemuBuildDriveDevStr(virDomainDefPtr def, > virBufferAddLit(&opt, "virtio-blk-device"); > } else { > virBufferAddLit(&opt, "virtio-blk-pci"); > + if (disk->iothread > 0) > + virBufferAsprintf(&opt, ",iothread=libvirtIothread%u", > + disk->iothread); You are using the def->iothread only to format it with virtio disks, but ... [1] > } > qemuBuildIoEventFdStr(&opt, disk->ioeventfd, qemuCaps); > if (disk->event_idx && > @@ -6614,6 +6617,31 @@ qemuBuildNumaArgStr(virQEMUDriverConfigPtr cfg, > } > > > +bool > +qemuDomainIothreadsAvailable(virDomainDefPtr def, > + virQEMUCapsPtr qemuCaps, > + virDomainDiskDefPtr disk) > +{ > + bool inuse; > + const char *src = virDomainDiskGetSource(disk); > + > + if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_IOTHREAD) || > + !def->iothreadmap) { > + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, > + _("IOThreads not supported for this QEMU " > + "for disk '%s'"), src); > + return false; > + } > + if (virBitmapGetBit(def->iothreadmap, disk->iothread, &inuse) || inuse) { > + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, > + _("IOThread '%u' for disk '%s' is already " > + "being used"), disk->iothread, src); Some disks may not have source set (empty cdrom drive), so it should probably be NULLSTR(src), but I think ""IOThread '%u' used multiple times" is more than enough. This leads me to a code simplification idea. If you checked QEMU_CAPS_OBJECT_IOTHREAD when creating the iothread objects it's enough to make virBitmapGetBit() handle NULL bitmap carefully and then just virBitmapGetBit() the bit the same way. And if the message does not output the disk name (src), this whole function can be thrown away and instead of doing: if (!qemuDomainIothreadsAvailable(def, qemuCaps, disk)) goto error; you'd do: if (virBitmapGetBit(def->iothreadmap, disk->iothread, &tmp) || tmp) virReportError(...);

Just an idea, though, not a requirement ;) If you keep it in a separate function, though, I'd suggest checking the range and reporting specific error, because when testing I got for example this error: "IOThread '3' for disk '(null)' is already being used" even though it clearly wasn't; I just had only 1 or 2 I/O threads created. > + return false; > + } > + return true; > +} > + > + > static int > qemuBuildGraphicsVNCCommandLine(virQEMUDriverConfigPtr cfg, > virCommandPtr cmd, > @@ -8055,6 +8083,13 @@ qemuBuildCommandLine(virConnectPtr conn, > disk->src->driverName, disk->src->path); > goto error; > } > + > + /* Check iothreads relationship */ > + if (disk->iothread > 0) { > + if (!qemuDomainIothreadsAvailable(def, qemuCaps, disk)) > + goto error; > + ignore_value(virBitmapSetBit(def->iothreadmap, disk->iothread)); > + } > } > [1] ... here you check it for all disks. And it's kept in the domain definition for all disks as well. Maybe removing it from unsupported disks and checking(+building) the iothreadmap could be done in qemuDomainDefPostParse().

> if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE)) { > diff --git a/src/qemu/qemu_command.h b/src/qemu/qemu_command.h > index 633ff71..bec6c14 100644 > --- a/src/qemu/qemu_command.h > +++ b/src/qemu/qemu_command.h > @@ -81,6 +81,11 @@ virCommandPtr qemuBuildCommandLine(virConnectPtr conn, > bool forXMLToArgv) > ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(11); > > +bool > +qemuDomainIothreadsAvailable(virDomainDefPtr def, > + virQEMUCapsPtr qemuCaps, > + virDomainDiskDefPtr disk); > + > /* Generate '-device' string for chardev device */ > int > qemuBuildChrDeviceStr(char **deviceStr, > diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c > index a364c52..720220d 100644 > --- a/src/qemu/qemu_hotplug.c > +++ b/src/qemu/qemu_hotplug.c > @@ -335,6 +335,11 @@ qemuDomainAttachVirtioDiskDevice(virConnectPtr conn, > } > } > > + if (disk->iothread > 0) { > + if (!qemuDomainIothreadsAvailable(vm->def, priv->qemuCaps, disk)) > + goto cleanup; > + } > + > if (qemuDomainPrepareDisk(driver, vm, disk, NULL, false) < 0) > goto cleanup; > > @@ -396,6 +401,9 @@ qemuDomainAttachVirtioDiskDevice(virConnectPtr conn, > if (ret < 0) > goto error; > > + if (disk->iothread && vm->def->iothreadmap) > + ignore_value(virBitmapSetBit(vm->def->iothreadmap, disk->iothread)); > + > virDomainDiskInsertPreAlloced(vm->def, disk); > > cleanup: From the names of the functions I see in these two hunks I guess this is ignored for non-virtio disks, which is a difference to cold-plugging non-virtio disks. The PostParse() modification I suggest above would take care of that.