Re: [Qemu-devel] [PATCH v3 2/5] pc, pc-dimm: Factor out reusable parts in pc_dimm_plug to a separate routine

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

On Fri, Jun 26, 2015 at 10:21:54AM +0200, Igor Mammedov wrote:
> On Fri, 26 Jun 2015 09:36:01 +0530
> Bharata B Rao <bharata@linux.vnet.ibm.com> wrote:
> 
> > pc_dimm_plug() has code that will be needed for memory plug handlers
> > in other archs too. Extract code from pc_dimm_plug() into a generic
> > routine pc_dimm_memory_plug() that resides in pc-dimm.c. Also
> > correspondingly refactor re-usable unplug code into pc_dimm_memory_unplug().
> > 
> > Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> thanks for splitting, much easier to review.

Yes it is much easier to see the changes and thanks for the review.

> 
> 
> > ---
> >  hw/i386/pc.c             | 66 ++++-----------------------------------
> >  hw/mem/pc-dimm.c         | 80 ++++++++++++++++++++++++++++++++++++++++++++++++
> >  include/hw/mem/pc-dimm.h |  4 +++
> >  3 files changed, 90 insertions(+), 60 deletions(-)
> > 
> > diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> > index e51c3be..cb57612 100644
> > --- a/hw/i386/pc.c
> > +++ b/hw/i386/pc.c
> > @@ -64,7 +64,6 @@
> >  #include "hw/pci/pci_host.h"
> >  #include "acpi-build.h"
> >  #include "hw/mem/pc-dimm.h"
> > -#include "trace.h"
> >  #include "qapi/visitor.h"
> >  #include "qapi-visit.h"
> >  
> > @@ -1554,88 +1553,35 @@ void ioapic_init_gsi(GSIState *gsi_state, const char *parent_name)
> >  static void pc_dimm_plug(HotplugHandler *hotplug_dev,
> >                           DeviceState *dev, Error **errp)
> >  {
> > -    int slot;
> >      HotplugHandlerClass *hhc;
> >      Error *local_err = NULL;
> >      PCMachineState *pcms = PC_MACHINE(hotplug_dev);
> > -    MachineState *machine = MACHINE(hotplug_dev);
> >      PCDIMMDevice *dimm = PC_DIMM(dev);
> >      PCDIMMDeviceClass *ddc = PC_DIMM_GET_CLASS(dimm);
> >      MemoryRegion *mr = ddc->get_memory_region(dimm);
> > -    uint64_t existing_dimms_capacity = 0;
> >      uint64_t align = TARGET_PAGE_SIZE;
> > -    uint64_t addr;
> > -
> > -    addr = object_property_get_int(OBJECT(dimm), PC_DIMM_ADDR_PROP, &local_err);
> > -    if (local_err) {
> > -        goto out;
> > -    }
> >  
> >      if (memory_region_get_alignment(mr) && pcms->enforce_aligned_dimm) {
> >          align = memory_region_get_alignment(mr);
> >      }
> >  
> > -    addr = pc_dimm_get_free_addr(pcms->hotplug_memory.base,
> > -                                 memory_region_size(&pcms->hotplug_memory.mr),
> > -                                 !addr ? NULL : &addr, align,
> > -                                 memory_region_size(mr), &local_err);
> > -    if (local_err) {
> > -        goto out;
> > -    }
> > -
> > -    existing_dimms_capacity = pc_existing_dimms_capacity(&local_err);
> > -    if (local_err) {
> > -        goto out;
> > -    }
> > -
> > -    if (existing_dimms_capacity + memory_region_size(mr) >
> > -        machine->maxram_size - machine->ram_size) {
> > -        error_setg(&local_err, "not enough space, currently 0x%" PRIx64
> > -                   " in use of total hot pluggable 0x" RAM_ADDR_FMT,
> > -                   existing_dimms_capacity,
> > -                   machine->maxram_size - machine->ram_size);
> > -        goto out;
> > -    }
> > -
> > -    object_property_set_int(OBJECT(dev), addr, PC_DIMM_ADDR_PROP, &local_err);
> > -    if (local_err) {
> > -        goto out;
> > -    }
> > -    trace_mhp_pc_dimm_assigned_address(addr);
> > -
> > -    slot = object_property_get_int(OBJECT(dev), PC_DIMM_SLOT_PROP, &local_err);
> > -    if (local_err) {
> > -        goto out;
> > -    }
> > -
> > -    slot = pc_dimm_get_free_slot(slot == PC_DIMM_UNASSIGNED_SLOT ? NULL : &slot,
> > -                                 machine->ram_slots, &local_err);
> > -    if (local_err) {
> > -        goto out;
> > -    }
> > -    object_property_set_int(OBJECT(dev), slot, PC_DIMM_SLOT_PROP, &local_err);
> > -    if (local_err) {
> > -        goto out;
> > -    }
> > -    trace_mhp_pc_dimm_assigned_slot(slot);
> > -
> >      if (!pcms->acpi_dev) {
> >          error_setg(&local_err,
> >                     "memory hotplug is not enabled: missing acpi device");
> >          goto out;
> >      }
> >  
> > -    if (kvm_enabled() && !kvm_has_free_slot(machine)) {
> > -        error_setg(&local_err, "hypervisor has no free memory slots left");
> > +    pc_dimm_memory_plug(dev, &pcms->hotplug_memory, mr, align, &local_err);
> > +    if (local_err) {
> >          goto out;
> >      }
> >  
> > -    memory_region_add_subregion(&pcms->hotplug_memory.mr,
> > -                                addr - pcms->hotplug_memory.base, mr);
> > -    vmstate_register_ram(mr, dev);
> > -
> >      hhc = HOTPLUG_HANDLER_GET_CLASS(pcms->acpi_dev);
> >      hhc->plug(HOTPLUG_HANDLER(pcms->acpi_dev), dev, &local_err);
> > +    if (local_err) {
> > +        pc_dimm_memory_unplug(dev, &pcms->hotplug_memory, mr);
> > +    }
> You are adding something new while patch claims to be just moving code.
> I'm not sure it's save to call unplug here if hhc->plug() failed
> since it might have triggered guest visible side effects.

In sPAPR, the routine equivalent to hhc->plug() could fail and
I needed pc_dimm_memory_unplug() to recover. But now I have rearranged
the code there to ensure that it never fails like in x86. However
I need pc_dimm_memory_unplug() nevertheless in sPAPR.

> 
> I'd just drop this hunk and leave original code,
> on top of that extra patch for hhc->plug(s/local_err/error_abort/)
> might make a sense since hhc->plug() should never fail and if it's
> then we should fix error in code instead of trying to recover.

I have added a small patch for this in my series.

> 
> >  out:
> >      error_propagate(errp, local_err);
> >  }
> > diff --git a/hw/mem/pc-dimm.c b/hw/mem/pc-dimm.c
> > index e70633d..98971b7 100644
> > --- a/hw/mem/pc-dimm.c
> > +++ b/hw/mem/pc-dimm.c
> > @@ -23,12 +23,92 @@
> >  #include "qapi/visitor.h"
> >  #include "qemu/range.h"
> >  #include "sysemu/numa.h"
> > +#include "sysemu/kvm.h"
> > +#include "trace.h"
> >  
> >  typedef struct pc_dimms_capacity {
> >       uint64_t size;
> >       Error    **errp;
> >  } pc_dimms_capacity;
> >  
> > +void pc_dimm_memory_plug(DeviceState *dev, MemoryHotplugState *hpms,
> > +                         MemoryRegion *mr, uint64_t align, Error **errp)
> > +{
> > +    int slot;
> > +    MachineState *machine = MACHINE(qdev_get_machine());
> > +    PCDIMMDevice *dimm = PC_DIMM(dev);
> > +    Error *local_err = NULL;
> > +    uint64_t existing_dimms_capacity = 0;
> > +    uint64_t addr;
> > +
> > +    addr = object_property_get_int(OBJECT(dimm), PC_DIMM_ADDR_PROP, &local_err);
> > +    if (local_err) {
> > +        goto out;
> > +    }
> > +
> > +    addr = pc_dimm_get_free_addr(hpms->base,
> > +                                 memory_region_size(&hpms->mr),
> > +                                 !addr ? NULL : &addr, align,
> > +                                 memory_region_size(mr), &local_err);
> > +    if (local_err) {
> > +        goto out;
> > +    }
> > +
> > +    existing_dimms_capacity = pc_existing_dimms_capacity(&local_err);
> > +    if (local_err) {
> > +        goto out;
> > +    }
> > +
> > +    if (existing_dimms_capacity + memory_region_size(mr) >
> > +        machine->maxram_size - machine->ram_size) {
> > +        error_setg(&local_err, "not enough space, currently 0x%" PRIx64
> > +                   " in use of total hot pluggable 0x" RAM_ADDR_FMT,
> > +                   existing_dimms_capacity,
> > +                   machine->maxram_size - machine->ram_size);
> > +        goto out;
> > +    }
> > +
> > +    object_property_set_int(OBJECT(dev), addr, PC_DIMM_ADDR_PROP, &local_err);
> > +    if (local_err) {
> > +        goto out;
> > +    }
> > +    trace_mhp_pc_dimm_assigned_address(addr);
> > +
> > +    slot = object_property_get_int(OBJECT(dev), PC_DIMM_SLOT_PROP, &local_err);
> > +    if (local_err) {
> > +        goto out;
> > +    }
> > +
> > +    slot = pc_dimm_get_free_slot(slot == PC_DIMM_UNASSIGNED_SLOT ? NULL : &slot,
> > +                                 machine->ram_slots, &local_err);
> > +    if (local_err) {
> > +        goto out;
> > +    }
> > +    object_property_set_int(OBJECT(dev), slot, PC_DIMM_SLOT_PROP, &local_err);
> > +    if (local_err) {
> > +        goto out;
> > +    }
> > +    trace_mhp_pc_dimm_assigned_slot(slot);
> > +
> > +    if (kvm_enabled() && !kvm_has_free_slot(machine)) {
> > +        error_setg(&local_err, "hypervisor has no free memory slots left");
> > +        goto out;
> > +    }
> > +
> > +    memory_region_add_subregion(&hpms->mr, addr - hpms->base, mr);
> > +    vmstate_register_ram(mr, dev);
> > +
> > +out:
> > +    error_propagate(errp, local_err);
> > +}
> > +
> > +void pc_dimm_memory_unplug(DeviceState *dev, MemoryHotplugState *hpms,
> > +                           MemoryRegion *mr)
> > +{
> > +    memory_region_del_subregion(&hpms->mr, mr);
> > +    vmstate_unregister_ram(mr, dev);
> > +}
> if you adding this here then you probably should be removing/replacing
> related hunks from pc.c, I don't see it in this patch.

In v2, I was calling this routine from pc_dimm_unplug, but somehow missed
this hunk during rebasing in v3.

I have addressed all you comments for this version and ready with next
version. However will wait till monday before respinning to see if I
am required to do more changes.

Regards,
Bharata.