Re: [Qemu-devel] [PATCH] hw/pci: completed master-abort emulation

[Marcel Apfelbaum <marcel.a@redhat.com>]

On Mon, 2013-09-23 at 14:27 +0300, Michael S. Tsirkin wrote:
> On Mon, Sep 23, 2013 at 02:01:17PM +0300, Marcel Apfelbaum wrote:
> > This patch is implemented on top of series:
> > [PATCH v5 0/3] pci: implement upstream master abort protocol
> > 
> > Added "master abort io" background region for PCIBus.
> > 
> > Added "master abort mem" region to catch transactions initiated
> > by pci devices targeted to unassigned addresses.
> > 
> > Enabled "master abort" regions for PCI-2-PCI bridge's secondary bus.
> > 
> > Set "Received Master Abort" Bit on Status/Secondary Status
> > register as defined in the PCI Spec.
> > 
> > Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
> 
> I think it will be easier to review the complete
> series, not an incremental patch.
Should I combine this with the prev series without the
memory patches?

> 
> We probably need to think what's the right thing
> to do for master abort mode since we do not
> emulate SERR. Do we make it writeable at all?
Master abort mode can be enabled. (Tested)

> 
> It's a pci only bit:
> 	When the Master-Abort Mode bit is cleared and a posted write transaction
> 	forwarded by the
> 	bridge terminates with a Master-Abort, no error is reported (note that
> 	the Master-Abort bit
> 	is still set). When the Master-Abort Mode bit is set and a posted write
> 	transaction forwarded
> 	by the bridge terminates with a Master-Abort on the destination bus, the
> 	bridge must:
> 	Assert SERR# on the primary interfaceCommand register)
> 	(if enabled by the SERR# Enable bitin the
> 	Set the Signaled System Errorbit in the Command register)
> 	bitin the Status register (if enabled by the SERR# Enable)
> 
> one way to do this would be not to set Master-Abort bit even
> though spec says we should, and pretend there was no error.
Maybe we can just not allow to set "Master abort mode"
in BRIDGE_CONTROL register. It is a cleaner way (I think)
considering we don't emulate SERR.

> 
> > ---
> >  hw/pci/pci.c             | 115 ++++++++++++++++++++++++++++++++++++++++++-----
> >  hw/pci/pci_bridge.c      |  10 +++++
> >  include/hw/pci/pci.h     |   3 ++
> >  include/hw/pci/pci_bus.h |   1 +
> >  4 files changed, 118 insertions(+), 11 deletions(-)
> > 
> > diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> > index d8a1b11..1f4e707 100644
> > --- a/hw/pci/pci.c
> > +++ b/hw/pci/pci.c
> > @@ -283,17 +283,76 @@ const char *pci_root_bus_path(PCIDevice *dev)
> >      return rootbus->qbus.name;
> >  }
> >  
> > +static PCIDevice *pci_bus_find_host(PCIBus *bus)
> > +{
> > +    PCIDevice *dev;
> > +    int i;
> > +
> > +    for (i = 0; i < ARRAY_SIZE(bus->devices); ++i) {
> > +        dev = bus->devices[i];
> > +        if (dev) {
> > +            PCIDeviceClass *pc = PCI_DEVICE_GET_CLASS(dev);
> > +            if (pc->class_id == PCI_CLASS_BRIDGE_HOST) {
> 
> In fact you can do this easier:
> 	 pci_get_word(dev->config + PCI_CLASS_DEVICE) == PCI_CLASS_BRIDGE_HOST
Thanks, I'll change.
> 
> > +                return dev;
> > +            }
> > +        }
> > +    }
> > +
> > +    return NULL;
> > +}
> > +
> > +static void master_abort(void *opaque)
> > +{
> > +    PCIDevice *master_dev = NULL;
> > +    PCIDeviceClass *pc;
> > +    PCIBus *bus;
> > +    int downstream;
> 
> bool?
Yes, I'll change

> > +
> > +    if (object_dynamic_cast(OBJECT(opaque), TYPE_PCI_DEVICE)) {
> 
> Please don't do dynamic cast just because you can.
> You know very well what kind of object you pass
> when you create the MR.
> So just call the appropriate function.
I wanted to merge the code for all 3 entities involved:
root PCIBus, PCIBus behind a bridge, and PCIDevice.
The region for merge was to use the same master_abort_mem_ops
because there are the same operations that must be done:
return -1 (0xFFF...) and set master abort received bit. 

> 
> > +        master_dev = PCI_DEVICE(opaque);
> > +        bus = master_dev->bus;
> > +        while (!pci_bus_is_root(bus)) {
> > +            master_dev = bus->parent_dev;
> > +            bus = master_dev->bus;
> > +        }
> > +        downstream = 0;
> > +    }
> > +
> > +    if (object_dynamic_cast(OBJECT(opaque), TYPE_PCI_BUS)) {
> > +        bus = PCI_BUS(opaque);
> > +        if (pci_bus_is_root(bus)) {
> > +            master_dev = pci_bus_find_host(bus);
> > +        } else { /* bus behind a PCI-2-PCI bridge */
> > +            master_dev = bus->parent_dev;
> > +        }
> 
> So the reason for this is that device to device MA
> is still not implemented here, correct?
Nope, the above code differentiate 2 scenarios:
1. the bus is the root bus => look for host bridge
   to update STATUS register
2. the bus is bridge's secondary bus =>
   update bridge STATUS register
"Device 2 Device" is handled implicitly because we have
a background region covering all device's target memory

> If it was it would be just one instance of it.
> I'm not saying this must block this patch, however
> there should be a code comment to this effect,
> and commit log should mention this explicitly.
As above, "Device 2 Device" is handled implicit
> 
> > +        downstream = 1;
> > +    }
> > +
> > +    assert(master_dev);
> > +    pc = PCI_DEVICE_GET_CLASS(master_dev);
> > +
> 
> There's very little common code between devices and
> buses. So just use 2 functions.
As stated above:
The region for merge was to use the same master_abort_mem_ops
because there are the same operations that must be done:
return -1 (0xFFF...) and set master abort received bit.
Separating them will result in some code duplication.
The read and write methods are the same, but would call different
"master_abort" methods.
If it does bother you the down casting anyway, I'll change.

> 
> > +    if (downstream && pc->is_bridge) {
> > +        pci_word_test_and_set_mask(master_dev->config + PCI_SEC_STATUS,
> > +                                   PCI_STATUS_REC_MASTER_ABORT);
> > +    } else {
> > +        pci_word_test_and_set_mask(master_dev->config + PCI_STATUS,
> > +                                   PCI_STATUS_REC_MASTER_ABORT);
> > +    }
> > +}
> > +
> >  static uint64_t master_abort_mem_read(void *opaque, hwaddr addr, unsigned size)
> >  {
> > -   return -1ULL;
> 
> I didn't notice but this means there were 3 spaces here in previous
> patch?
yes :(, checkpatch didn't catch it

Thanks for the review,
Marcel

> 
> > +    master_abort(opaque);
> > +    return -1ULL;
> >  }
> >  
> >  static void master_abort_mem_write(void *opaque, hwaddr addr, uint64_t val,
> >                                     unsigned size)
> >  {
> > +    master_abort(opaque);
> >  }
> >  
> > -static const MemoryRegionOps master_abort_mem_ops = {
> > +static const MemoryRegionOps master_abort_ops = {
> >      .read = master_abort_mem_read,
> >      .write = master_abort_mem_write,
> >      .endianness = DEVICE_LITTLE_ENDIAN,
> > @@ -301,6 +360,23 @@ static const MemoryRegionOps master_abort_mem_ops = {
> >  
> >  #define MASTER_ABORT_MEM_PRIORITY INT_MIN
> >  
> > +void pci_bus_master_abort_init(PCIBus *bus, const char *mem, const char *io)
> > +{
> > +    memory_region_init_io(&bus->master_abort_mem, OBJECT(bus),
> > +                          &master_abort_ops, bus, mem,
> > +                          memory_region_size(bus->address_space_mem));
> > +    memory_region_add_subregion_overlap(bus->address_space_mem,
> > +                                        0, &bus->master_abort_mem,
> > +                                        MASTER_ABORT_MEM_PRIORITY);
> > +
> > +    memory_region_init_io(&bus->master_abort_io, OBJECT(bus),
> > +                          &master_abort_ops, bus, io,
> > +                          memory_region_size(bus->address_space_io));
> > +    memory_region_add_subregion_overlap(bus->address_space_io,
> > +                                        0, &bus->master_abort_io,
> > +                                        MASTER_ABORT_MEM_PRIORITY);
> > +}
> > +
> >  static void pci_bus_init(PCIBus *bus, DeviceState *parent,
> >                           const char *name,
> >                           MemoryRegion *address_space_mem,
> > @@ -312,13 +388,8 @@ static void pci_bus_init(PCIBus *bus, DeviceState *parent,
> >      bus->address_space_mem = address_space_mem;
> >      bus->address_space_io = address_space_io;
> >  
> > -
> > -    memory_region_init_io(&bus->master_abort_mem, OBJECT(bus),
> > -                          &master_abort_mem_ops, bus, "pci-master-abort",
> > -                          memory_region_size(bus->address_space_mem));
> > -    memory_region_add_subregion_overlap(bus->address_space_mem,
> > -                                        0, &bus->master_abort_mem,
> > -                                        MASTER_ABORT_MEM_PRIORITY);
> > +    pci_bus_master_abort_init(bus, "pci-master-abort-mem",
> > +                              "pci-master-abort-io");
> >  
> >      /* host bridge */
> >      QLIST_INIT(&bus->child);
> > @@ -840,9 +911,24 @@ static PCIDevice *do_pci_register_device(PCIDevice *pci_dev, PCIBus *bus,
> >      pci_dev->bus = bus;
> >      dma_as = pci_device_iommu_address_space(pci_dev);
> >  
> > -    memory_region_init_alias(&pci_dev->bus_master_enable_region,
> > -                             OBJECT(pci_dev), "bus master",
> > +    memory_region_init(&pci_dev->bus_master_enable_region, NULL,
> > +                       "bus master", UINT64_MAX);
> > +
> > +    memory_region_init_io(&pci_dev->bus_master_abort_mem, OBJECT(bus),
> > +                          &master_abort_ops, OBJECT(pci_dev),
> > +                          "bus master master-abort",
> > +                          memory_region_size(&pci_dev->bus_master_enable_region));
> > +    memory_region_add_subregion_overlap(&pci_dev->bus_master_enable_region,
> > +                                        0, &pci_dev->bus_master_abort_mem,
> > +                                        MASTER_ABORT_MEM_PRIORITY);
> > +
> > +    memory_region_init_alias(&pci_dev->bus_master_dma_mem,
> > +                             OBJECT(pci_dev), "bus master dma",
> >                               dma_as->root, 0, memory_region_size(dma_as->root));
> > +    memory_region_add_subregion_overlap(&pci_dev->bus_master_enable_region,
> > +                                        0, &pci_dev->bus_master_dma_mem, 0);
> > +
> > +
> >      memory_region_set_enabled(&pci_dev->bus_master_enable_region, false);
> >      address_space_init(&pci_dev->bus_master_as, &pci_dev->bus_master_enable_region,
> >                         name);
> > @@ -901,6 +987,13 @@ static void do_pci_unregister_device(PCIDevice *pci_dev)
> >      pci_config_free(pci_dev);
> >  
> >      address_space_destroy(&pci_dev->bus_master_as);
> > +    memory_region_del_subregion(&pci_dev->bus_master_enable_region,
> > +                                &pci_dev->bus_master_dma_mem);
> > +    memory_region_del_subregion(&pci_dev->bus_master_enable_region,
> > +                                &pci_dev->bus_master_abort_mem);
> > +    memory_region_destroy(&pci_dev->bus_master_dma_mem);
> > +    memory_region_destroy(&pci_dev->bus_master_abort_mem);
> > +
> >      memory_region_destroy(&pci_dev->bus_master_enable_region);
> >  }
> >  
> > diff --git a/hw/pci/pci_bridge.c b/hw/pci/pci_bridge.c
> > index e6b22b8..56b682f 100644
> > --- a/hw/pci/pci_bridge.c
> > +++ b/hw/pci/pci_bridge.c
> > @@ -376,6 +376,10 @@ int pci_bridge_initfn(PCIDevice *dev, const char *typename)
> >      sec_bus->address_space_io = &br->address_space_io;
> >      memory_region_init(&br->address_space_io, OBJECT(br), "pci_bridge_io", 65536);
> >      br->windows = pci_bridge_region_init(br);
> > +
> > +    pci_bus_master_abort_init(sec_bus, "pci_bridge_master_abort_mem",
> > +                              "pci_bridge_master_abort_io");
> > +
> >      QLIST_INIT(&sec_bus->child);
> >      QLIST_INSERT_HEAD(&parent->child, sec_bus, sibling);
> >      return 0;
> > @@ -389,6 +393,12 @@ void pci_bridge_exitfn(PCIDevice *pci_dev)
> >      QLIST_REMOVE(&s->sec_bus, sibling);
> >      pci_bridge_region_del(s, s->windows);
> >      pci_bridge_region_cleanup(s, s->windows);
> > +    memory_region_del_subregion(s->sec_bus.address_space_mem,
> > +                                &s->sec_bus.master_abort_mem);
> > +    memory_region_del_subregion(s->sec_bus.address_space_io,
> > +                                &s->sec_bus.master_abort_io);
> > +    memory_region_destroy(&s->sec_bus.master_abort_mem);
> > +    memory_region_destroy(&s->sec_bus.master_abort_io);
> >      memory_region_destroy(&s->address_space_mem);
> >      memory_region_destroy(&s->address_space_io);
> >      /* qbus_free() is called automatically by qdev_free() */
> > diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
> > index 37979aa..d69e06d 100644
> > --- a/include/hw/pci/pci.h
> > +++ b/include/hw/pci/pci.h
> > @@ -242,6 +242,8 @@ struct PCIDevice {
> >      PCIIORegion io_regions[PCI_NUM_REGIONS];
> >      AddressSpace bus_master_as;
> >      MemoryRegion bus_master_enable_region;
> > +    MemoryRegion bus_master_dma_mem;
> > +    MemoryRegion bus_master_abort_mem;
> >  
> >      /* do not access the following fields */
> >      PCIConfigReadFunc *config_read;
> > @@ -357,6 +359,7 @@ PCIBus *pci_bus_new(DeviceState *parent, const char *name,
> >                      MemoryRegion *address_space_mem,
> >                      MemoryRegion *address_space_io,
> >                      uint8_t devfn_min, const char *typename);
> > +void pci_bus_master_abort_init(PCIBus *bus, const char *mem, const char *io);
> >  void pci_bus_irqs(PCIBus *bus, pci_set_irq_fn set_irq, pci_map_irq_fn map_irq,
> >                    void *irq_opaque, int nirq);
> >  int pci_bus_get_irq_level(PCIBus *bus, int irq_num);
> > diff --git a/include/hw/pci/pci_bus.h b/include/hw/pci/pci_bus.h
> > index 2ad5edb..57b1541 100644
> > --- a/include/hw/pci/pci_bus.h
> > +++ b/include/hw/pci/pci_bus.h
> > @@ -24,6 +24,7 @@ struct PCIBus {
> >      MemoryRegion *address_space_mem;
> >      MemoryRegion *address_space_io;
> >      MemoryRegion master_abort_mem;
> > +    MemoryRegion master_abort_io;
> >  
> >      QLIST_HEAD(, PCIBus) child; /* this will be replaced by qdev later */
> >      QLIST_ENTRY(PCIBus) sibling;/* this will be replaced by qdev later */
> > -- 
> > 1.8.3.1