Re: [Qemu-devel] [Qemu-ppc] [PATCH v9 1/6] hw/ppc/spapr.c: adding pending_dimm_unplugs to sPAPRMachineState

[Daniel Henrique Barboza <danielhb@linux.vnet.ibm.com>]

On 05/12/2017 03:04 AM, David Gibson wrote:
> On Fri, May 05, 2017 at 05:47:41PM -0300, Daniel Henrique Barboza wrote:
>> The LMB DRC release callback, spapr_lmb_release(), uses an opaque
>> parameter, a sPAPRDIMMState struct that stores the current LMBs that
>> are allocated to a DIMM (nr_lmbs). After each call to this callback,
>> the nr_lmbs is decremented by one and, when it reaches zero, the callback
>> proceeds with the qdev calls to hot unplug the LMB.
>>
>> Using drc->detach_cb_opaque is problematic because it can't be migrated in
>> the future DRC migration work. This patch makes the following changes to
>> eliminate the usage of this opaque callback inside spapr_lmb_release:
>>
>> - sPAPRDIMMState was moved from spapr.c and added to spapr.h. A new
>> attribute called 'addr' was added to it. This is used as an unique
>> identifier to associate a sPAPRDIMMState to a PCDIMM element.
>>
>> - sPAPRMachineState now hosts a new QTAILQ called 'pending_dimm_unplugs'.
>> This queue of sPAPRDIMMState elements will store the DIMM state of DIMMs
>> that are currently going under an unplug process.
>>
>> - spapr_lmb_release() will now retrieve the nr_lmbs value by getting the
>> correspondent sPAPRDIMMState. A helper function called spapr_dimm_get_address
>> was created to fetch the address of a PCDIMM device inside spapr_lmb_release.
>> When nr_lmbs reaches zero and the callback proceeds with the qdev hot unplug
>> calls, the sPAPRDIMMState struct is removed from spapr->pending_dimm_unplugs.
>>
>> After these changes, the opaque argument for spapr_lmb_release is now
>> unused and is passed as NULL inside spapr_del_lmbs. This and the other
>> opaque arguments can now be safely removed from the code.
>>
>> Signed-off-by: Daniel Henrique Barboza <danielhb@linux.vnet.ibm.com>
> Urgh.  Moving this into the machine is really ugly.  Unfortunately, I
> can't quickly see a better way to accomplish what you need.  So I
> guess this approach is ok, with the hope that we can find a better way
> in future.

Agreed.

>
> There are a few more superficial problems to address, though.
>
>> ---
>>   hw/ppc/spapr.c         | 54 ++++++++++++++++++++++++++++++++++++++++++++------
>>   include/hw/ppc/spapr.h | 17 ++++++++++++++++
>>   2 files changed, 65 insertions(+), 6 deletions(-)
>>
>> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
>> index 80d12d0..346c827 100644
>> --- a/hw/ppc/spapr.c
>> +++ b/hw/ppc/spapr.c
>> @@ -2043,6 +2043,7 @@ static void ppc_spapr_init(MachineState *machine)
>>       msi_nonbroken = true;
>>   
>>       QLIST_INIT(&spapr->phbs);
>> +    QTAILQ_INIT(&spapr->pending_dimm_unplugs);
>>   
>>       /* Allocate RMA if necessary */
>>       rma_alloc_size = kvmppc_alloc_rma(&rma);
>> @@ -2596,20 +2597,32 @@ out:
>>       error_propagate(errp, local_err);
>>   }
>>   
>> -typedef struct sPAPRDIMMState {
>> -    uint32_t nr_lmbs;
>> -} sPAPRDIMMState;
>> +static uint64_t spapr_dimm_get_address(PCDIMMDevice *dimm)
>> +{
>> +    Error *local_err = NULL;
>> +    uint64_t addr;
>> +    addr = object_property_get_int(OBJECT(dimm), PC_DIMM_ADDR_PROP,
>> +                                   &local_err);
>> +    if (local_err) {
>> +        error_propagate(&error_abort, local_err);
>> +        return 0;
>> +    }
>> +    return addr;
>> +}
>>   
>>   static void spapr_lmb_release(DeviceState *dev, void *opaque)
>>   {
>> -    sPAPRDIMMState *ds = (sPAPRDIMMState *)opaque;
>>       HotplugHandler *hotplug_ctrl;
>>   
> No need for this blank line in the middle of declarations.
>
>> +    uint64_t addr = spapr_dimm_get_address(PC_DIMM(dev));
>> +    sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
>> +    sPAPRDIMMState *ds = spapr_pending_dimm_unplugs_find(spapr, addr);
>> +
>>       if (--ds->nr_lmbs) {
>>           return;
>>       }
>>   
>> -    g_free(ds);
>> +    spapr_pending_dimm_unplugs_remove(spapr, ds);
>>   
>>       /*
>>        * Now that all the LMBs have been removed by the guest, call the
>> @@ -2626,17 +2639,20 @@ static void spapr_del_lmbs(DeviceState *dev, uint64_t addr_start, uint64_t size,
>>       sPAPRDRConnectorClass *drck;
>>       uint32_t nr_lmbs = size / SPAPR_MEMORY_BLOCK_SIZE;
>>       int i;
>> +    sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
>>       sPAPRDIMMState *ds = g_malloc0(sizeof(sPAPRDIMMState));
>>       uint64_t addr = addr_start;
>>   
>>       ds->nr_lmbs = nr_lmbs;
>> +    ds->addr = addr_start;
>> +    spapr_pending_dimm_unplugs_add(spapr, ds);
>>       for (i = 0; i < nr_lmbs; i++) {
>>           drc = spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_LMB,
>>                   addr / SPAPR_MEMORY_BLOCK_SIZE);
>>           g_assert(drc);
>>   
>>           drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
>> -        drck->detach(drc, dev, spapr_lmb_release, ds, errp);
>> +        drck->detach(drc, dev, spapr_lmb_release, NULL, errp);
>>           addr += SPAPR_MEMORY_BLOCK_SIZE;
>>       }
>>   
>> @@ -3515,3 +3531,29 @@ static void spapr_machine_register_types(void)
>>   }
>>   
>>   type_init(spapr_machine_register_types)
>> +
>> +sPAPRDIMMState *spapr_pending_dimm_unplugs_find(sPAPRMachineState *spapr,
>> +                                                uint64_t addr)
>> +{
>> +    sPAPRDIMMState *dimm_state = NULL;
>> +    QTAILQ_FOREACH(dimm_state, &spapr->pending_dimm_unplugs, next) {
>> +        if (dimm_state->addr == addr) {
>> +            break;
>> +        }
>> +    }
>> +    return dimm_state;
>> +}
>> +
>> +void spapr_pending_dimm_unplugs_add(sPAPRMachineState *spapr,
>> +                                   sPAPRDIMMState *dimm_state)
>> +{
>> +    g_assert(!spapr_pending_dimm_unplugs_find(spapr, dimm_state->addr));
>> +    QTAILQ_INSERT_HEAD(&spapr->pending_dimm_unplugs, dimm_state, next);
>> +}
>> +
>> +void spapr_pending_dimm_unplugs_remove(sPAPRMachineState *spapr,
>> +                                      sPAPRDIMMState *dimm_state)
>> +{
>> +    QTAILQ_REMOVE(&spapr->pending_dimm_unplugs, dimm_state, next);
>> +    g_free(dimm_state);
>> +}
>> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
>> index 5802f88..3e2b5ab 100644
>> --- a/include/hw/ppc/spapr.h
>> +++ b/include/hw/ppc/spapr.h
>> @@ -32,6 +32,7 @@ struct sPAPRRTCState {
>>       int64_t ns_offset;
>>   };
>>   
>> +typedef struct sPAPRDIMMState sPAPRDIMMState;
>>   typedef struct sPAPRMachineClass sPAPRMachineClass;
>>   
>>   #define TYPE_SPAPR_MACHINE      "spapr-machine"
>> @@ -104,6 +105,9 @@ struct sPAPRMachineState {
>>       /* RTAS state */
>>       QTAILQ_HEAD(, sPAPRConfigureConnectorState) ccs_list;
>>   
>> +    /* pending DIMM unplug queue */
>> +    QTAILQ_HEAD(, sPAPRDIMMState) pending_dimm_unplugs;
>> +
>>       /*< public >*/
>>       char *kvm_type;
>>       MemoryHotplugState hotplug_memory;
>> @@ -646,6 +650,19 @@ struct sPAPRConfigureConnectorState {
>>   
>>   void spapr_ccs_reset_hook(void *opaque);
>>   
>> +struct sPAPRDIMMState {
>> +    uint64_t addr;
>> +    uint32_t nr_lmbs;
>> +    QTAILQ_ENTRY(sPAPRDIMMState) next;
>> +};
>> +
>> +sPAPRDIMMState *spapr_pending_dimm_unplugs_find(sPAPRMachineState *spapr,
>> +                                               uint64_t addr);
>> +void spapr_pending_dimm_unplugs_add(sPAPRMachineState *spapr,
>> +                                   sPAPRDIMMState *dimm_state);
>> +void spapr_pending_dimm_unplugs_remove(sPAPRMachineState *spapr,
>> +                                      sPAPRDIMMState *dimm_state);
>> +
> AFAICT all these new functions are only used in spapr.c, even in the
> rest of the series.  So they should be static, and not in the header
> file.  Likewise the structure definition.
>
>>   void spapr_rtc_read(sPAPRRTCState *rtc, struct tm *tm, uint32_t *ns);
>>   int spapr_rtc_import_offset(sPAPRRTCState *rtc, int64_t legacy_offset);
>>