Re: [Qemu-devel] [Qemu-ppc] [PATCH 1/5] spapr: ensure device trees are always associated with DRC

[Jianjun Duan]

On 04/19/2016 09:30 PM, David Gibson wrote:
> On Fri, Apr 15, 2016 at 01:33:01PM -0700, Jianjun Duan wrote:
> > There are possible racing situations involving hotplug events and
> > guest migration. For cases where a hotplug event is migrated, or
> > the guest is in the process of fetching device tree at the time of
> > migration, we need to ensure the device tree is created and
> > associated with the corresponding DRC for devices that were
> > hotplugged on the source, but 'coldplugged' on the target.
> >
> > Signed-off-by: Jianjun Duan <address@hidden>
> This seems fairly sensible - should be harmless and a bit cleaner
> whether or not we strictly speaking need it.
>
> However, it is likely to conflict with some of the device tree
> construction cleanups I have in my pipeline, so it may well need
> rework for that.
Sure. It will need rework for CPU hotplug too.
> > ---
> >   hw/ppc/spapr.c     | 16 ++++++----------
> >   hw/ppc/spapr_pci.c | 12 +++++-------
> >   2 files changed, 11 insertions(+), 17 deletions(-)
> >
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index feaab08..af4745c 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -2132,15 +2132,6 @@ static void spapr_add_lmbs(DeviceState *dev, uint64_t 
> > addr, uint64_t size,
> >       int i, fdt_offset, fdt_size;
> >       void *fdt;
> >   
> > -    /*
> > -     * Check for DRC connectors and send hotplug notification to the
> > -     * guest only in case of hotplugged memory. This allows cold plugged
> > -     * memory to be specified at boot time.
> > -     */
> > -    if (!dev->hotplugged) {
> > -        return;
> > -    }
> > -
> >       for (i = 0; i < nr_lmbs; i++) {
> >           drc = spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_LMB,
> >                   addr/SPAPR_MEMORY_BLOCK_SIZE);
> > @@ -2154,7 +2145,12 @@ static void spapr_add_lmbs(DeviceState *dev, uint64_t 
> > addr, uint64_t size,
> >           drck->attach(drc, dev, fdt, fdt_offset, !dev->hotplugged, errp);
> >           addr += SPAPR_MEMORY_BLOCK_SIZE;
> >       }
> > -    spapr_hotplug_req_add_by_count(SPAPR_DR_CONNECTOR_TYPE_LMB, nr_lmbs);
> > +    /* send hotplug notification to the
> > +     * guest only in case of hotplugged memory
> > +     */
> > +    if (dev->hotplugged) {
> > +       spapr_hotplug_req_add_by_count(SPAPR_DR_CONNECTOR_TYPE_LMB, nr_lmbs);
> > +    }
> >   }
> >   
> >   static void spapr_memory_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
> > diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> > index 8c20d34..b179e42 100644
> > --- a/hw/ppc/spapr_pci.c
> > +++ b/hw/ppc/spapr_pci.c
> > @@ -1092,13 +1092,11 @@ static void spapr_phb_add_pci_device(sPAPRDRConnector 
> > *drc,
> >           spapr_tce_set_need_vfio(tcet, true);
> >       }
> >   
> > -    if (dev->hotplugged) {
> > -        fdt = create_device_tree(&fdt_size);
> > -        fdt_start_offset = spapr_create_pci_child_dt(phb, pdev, fdt, 0);
> > -        if (!fdt_start_offset) {
> > -            error_setg(errp, "Failed to create pci child device tree node");
> > -            goto out;
> > -        }
> > +    fdt = create_device_tree(&fdt_size);
> > +    fdt_start_offset = spapr_create_pci_child_dt(phb, pdev, fdt, 0);
> > +    if (!fdt_start_offset) {
> > +        error_setg(errp, "Failed to create pci child device tree node");
> > +        goto out;
> >       }
> >   
> >       drck->attach(drc, DEVICE(pdev),