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

[Jianjun Duan <duanj@linux.vnet.ibm.com>]

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 <duanj@linux.vnet.ibm.com>
> 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),