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Re: [libvirt] [PATCH 3/5] libvirt/qemu - support persistent modification of devices.



On Tue, 15 Mar 2011 15:55:51 -0600
Eric Blake <eblake redhat com> wrote:

> On 03/02/2011 06:11 PM, KAMEZAWA Hiroyuki wrote:
> >>From f7a997e3cd58cfac81e131afdd20c3691267831d Mon Sep 17 00:00:00 2001
> > From: KAMEZAWA Hiroyuki <kamezawa hiroyu jp fujitsu com>
> > Date: Thu, 3 Mar 2011 09:43:07 +0900
> > Subject: [PATCH 3/5] libivrt/qemu - support persistent modification of devices.
> > 
> > Now, virsh attach-***/detach-*** has --persistent option and
> > it can update XML definition of inactive domains.
> 
> Hmm, looking at the recent additions of other virsh persistent support,
> the single --persistent flag of virsh attach-{device,disk,interface} are
> a bit limited; --persistent means the same thing as --config, but we may
> need to add a counterpart --live option that specifies live only.  But
> cleaning up virsh to better expose the underlying flags is a separate
> patch; this patch only deals with implementing the flags internally.
> 
yes.

> > Now, disk and nic are supported in Xen, but none in qemu.
> 
> It would be nice to get all devices supported, but incremental is better
> than nothing at all.
> 
> > 
> > This patch adds a function for permanent modification for qemu.
> > Following patches will add disk/network suport.
> > 
> > TODO:
> >   - finally, need to do hotplug + XML modification for active domain.
> > 
> > Changelog v3->v4
> >   - fixed trailing white spaces.
> >   - splitted into 2 part and this patch only contains wrappers.
> > Changelog v2->v3:
> >   - clean ups.
> >   - handle all VIR_DOMAIN_DEVICE_MODIFY_XXX flags.
> > ---
> >  src/qemu/qemu_driver.c |  143 ++++++++++++++++++++++++++++++++++++++++++++----
> >  1 files changed, 131 insertions(+), 12 deletions(-)
> > 
> > diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> > index c9095bb..3248cdc 100644
> > --- a/src/qemu/qemu_driver.c
> > +++ b/src/qemu/qemu_driver.c
> > @@ -4099,16 +4099,131 @@ cleanup:
> >      return ret;
> >  }
> >  
> > -static int qemudDomainAttachDeviceFlags(virDomainPtr dom,
> > +/*
> > + * Attach a device given by XML, the change will be persistent
> > + * and domain XML definition file is updated.
> > + */
> > +static int qemuDomainAttachDevicePersistent(virDomainDefPtr vmdef,
> > +                                            virDomainDeviceDefPtr newdev)
> > +{
> > +
> > +    /* At first, check device confliction */
> 
> s/device confliction/for device support/
> 
will fix.

> > +    switch(newdev->type) {
> > +    default:
> > +        qemuReportError(VIR_ERR_INVALID_ARG, "%s",
> > +                        _("Sorry, the device is not suppored for now"));
> 
> s/suppored/supported/ (twice)
> 
will fix. ....I'll use spell checker.

> > +
> > +static int qemuDomainModifyDevicePersistent(virDomainPtr dom,
> >                                          const char *xml,
> 
> Indentation is not consistent.
> 
ok.


> > -                                        unsigned int flags) {
> > -    if (flags & VIR_DOMAIN_DEVICE_MODIFY_CONFIG) {
> > -        qemuReportError(VIR_ERR_OPERATION_INVALID,
> > -                        "%s", _("cannot modify the persistent configuration of a domain"));
> > +                                        unsigned int attach, int flags)
> > +{
> > +    struct qemud_driver *driver;
> > +    virDomainDeviceDefPtr device;
> > +    virDomainDefPtr vmdef;
> > +    virDomainObjPtr vm;
> > +    int ret = -1;
> > +
> > +    if (!dom || !dom->conn || !dom->name || !xml) {
> > +        qemuReportError(VIR_ERR_INTERNAL_ERROR,
> > +                        _("internal error : %s"),  __FUNCTION__);
> > +        return -1;
> > +    }
> > +    /*
> > +     * When both of MODIFY_CONFIG and MODIFY_LIVE is specified at the same time,
> > +     * return error for now. We should support this later.
> > +     */
> > +    if (flags & VIR_DOMAIN_DEVICE_MODIFY_LIVE) {
> > +        qemuReportError(VIR_ERR_INVALID_ARG, "%s",
> > +                        _("Now, cannot modify alive domain and its definition "
> > +                          "at the same time."));
> 
> It shouldn't be too hard to attempt supporting this now - after all, we
> already did just that with Taku Izumi's patch for virsh setmem.
> qemudDomainSetMemoryFlags can be a good reference point for how to
> implement a command that first validates all conditions required by the
> flags, then modifies the live configuration if requested and still live,
> then modifies the persistent configuration if requested.
> 

Can we do it in atomic ?


> I think there have been enough findings already (Wen's feedback has also
> been useful), as well as quite a bit of upstream churn that will require
> rebasing aspects of your patch, that I'll wait for v5 of this series; if
> you use 'git send-email --subject-prefix=PATCHv5', that will make it
> easier to recognize from the subject line that it is a resend.
> 

ok, will do.

Thanks,
-Kame


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