Re: [Qemu-devel] [Qemu-ppc] [RESEND PATCH v10 1/5] hw/ppc/spapr.c: adding pending_dimm_unplugs to sPAPRMachineState

[Daniel Henrique Barboza]

On 05/19/2017 01:26 AM, David Gibson wrote:
> On Thu, May 18, 2017 at 06:54:12PM -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 <address@hidden>
> > ---
> >   hw/ppc/spapr.c         | 57 +++++++++++++++++++++++++++++++++++++++++++++-----
> >   include/hw/ppc/spapr.h |  4 ++++
> >   2 files changed, 56 insertions(+), 5 deletions(-)
> >
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index 0980d73..b05abe5 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -2050,6 +2050,7 @@ 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);
> > @@ -2603,20 +2604,63 @@ out:
> >       error_propagate(errp, local_err);
> >   }
> >   
> > -typedef struct sPAPRDIMMState {
> > +struct sPAPRDIMMState {
> > +    uint64_t addr;
> Since you're not trying to migrate this any more, you can index the
> list by an actual PCDIMMDevice *, rather than the base address.
> You're already passing the DeviceState * for the DIMM around, so this
> will actually remove the address parameter from some functions.
Good idea.

> I think that could actually be done as a preliminary cleanup.  It also
> probably makes sense to merge spapr_del_lmbs() with
> spapr_memory_unplug_request(), they're both very small.

Ok.

> >       uint32_t nr_lmbs;
> > -} sPAPRDIMMState;
> > +    QTAILQ_ENTRY(sPAPRDIMMState) next;
> > +};
> > +
> > +static sPAPRDIMMState *spapr_pending_dimm_unplugs_find(sPAPRMachineState *s,
> > +                                                       uint64_t addr)
> > +{
> > +    sPAPRDIMMState *dimm_state = NULL;
> > +    QTAILQ_FOREACH(dimm_state, &s->pending_dimm_unplugs, next) {
> > +        if (dimm_state->addr == addr) {
> > +            break;
> > +        }
> > +    }
> > +    return dimm_state;
> > +}
> > +
> > +static 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);
> > +}
> > +
> > +static void spapr_pending_dimm_unplugs_remove(sPAPRMachineState *spapr,
> > +                                              sPAPRDIMMState *dimm_state)
> > +{
> > +    QTAILQ_REMOVE(&spapr->pending_dimm_unplugs, dimm_state, next);
> > +    g_free(dimm_state);
> > +}
> > +
> > +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;
> > +    uint64_t addr = spapr_dimm_get_address(PC_DIMM(dev));
> > +    sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
> I prefer not to access the machine as a global when possible.  I think
> it's preferable to pass down the spapr object from above -
> unplug_request() itself can get it from hotplug_dev.

I see that we have access to the hotplug_dev (HotplugHandler) in the end of
spapr_lmb_release:

    hotplug_ctrl = qdev_get_hotplug_handler(dev);

One alternative would be to move this call up in the function and then
retrieve the machine as unplug_request() does:

    hotplug_ctrl = qdev_get_hotplug_handler(dev);
    sPAPRMachineState *ms = SPAPR_MACHINE(hotplug_ctrl);



> > +    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
> > @@ -2633,17 +2677,20 @@ 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;
> >       }
> >   
> > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> > index 5802f88..9823296 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 */
> Perhaps update this to mention that it's a cache which can be
> regenerated when necessary.
Ok.
> > +    QTAILQ_HEAD(, sPAPRDIMMState) pending_dimm_unplugs;
> > +
> >       /*< public >*/
> >       char *kvm_type;
> >       MemoryHotplugState hotplug_memory;