Re: [Qemu-devel] [PATCH v4 3/3] hw/pci: handle downstream pci master abort

[Marcel Apfelbaum]

On Sun, 2013-09-15 at 20:30 +0300, Michael S. Tsirkin wrote:
> On Sun, Sep 15, 2013 at 07:16:41PM +0300, Marcel Apfelbaum wrote:
> > A MemoryRegion with negative priority was created and
> > it spans over all the pci address space.
> > It "intercepts" the accesses to unassigned pci
> > address space and will follow the pci spec:
> >  1. returns -1 on read
> >  2. does nothing on write
> > 
> > Note: setting the RECEIVED MASTER ABORT bit in the STATUS register
> >       of the device that initiated the transaction will be
> >       implemented in another series
> 
> Fine though I'd like to see how it all works
> together before applying.
> 
> > Note: This implementation handles only the reads/writes to
> >       the pci address space that are done by the cpu.(downstream)
> 
> Strange, I don't see where does the limitation come from.
> Looks like any read returns -1 - what did I miss.
Devices using IOMMU have a different way to get their
memory regions. I am not sure that master abort memory
region covers the scenario.
Anyway, the above statement was for the prev implementation,
I will remove it in the next version.

Thanks,
Marcel

> 
> > 
> > Signed-off-by: Marcel Apfelbaum <address@hidden>
> > ---
> > Changes from v3:
> >  - Addresses Michael S. Tsirkin comments
> >    - Changed the name of the new Memory region to master_abort_mem
> >    - Made master abort priority INT_MIN instead of -1
> >  - Removed handling of RECEIVED MASTER ABORT BIT; it will be taken
> >    care in a different series
> > 
> > Changes from v1:
> >  - "pci-unassigned-mem" MemoryRegion resides now in PCIBus and not on
> >     various Host Bridges
> >  - "pci-unassgined-mem" does not have a ".valid.accept" field and
> >     implements read write methods
> > 
> >  hw/pci/pci.c             | 27 +++++++++++++++++++++++++++
> >  include/hw/pci/pci_bus.h |  1 +
> >  2 files changed, 28 insertions(+)
> > 
> > diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> > index d00682e..9b12375 100644
> > --- a/hw/pci/pci.c
> > +++ b/hw/pci/pci.c
> > @@ -283,6 +283,24 @@ const char *pci_root_bus_path(PCIDevice *dev)
> >      return rootbus->qbus.name;
> >  }
> >  
> > +static uint64_t master_abort_mem_read(void *opaque, hwaddr addr, unsigned 
> > size)
> > +{
> > +   return -1ULL;
> > +}
> > +
> > +static void master_abort_mem_write(void *opaque, hwaddr addr, uint64_t val,
> > +                                   unsigned size)
> > +{
> > +}
> > +
> > +static const MemoryRegionOps master_abort_mem_ops = {
> > +    .read = master_abort_mem_read,
> > +    .write = master_abort_mem_write,
> > +    .endianness = DEVICE_NATIVE_ENDIAN,
> > +};
> > +
> 
> Please make it little endian.
> DEVICE_NATIVE_ENDIAN is almost always a bug.
> 
> > +#define MASTER_ABORT_MEM_PRIORITY INT_MIN
> > +
> >  static void pci_bus_init(PCIBus *bus, DeviceState *parent,
> >                           const char *name,
> >                           MemoryRegion *address_space_mem,
> > @@ -294,6 +312,15 @@ 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,
> > +                                        bus->address_space_mem->addr,
> > +                                        &bus->master_abort_mem,
> > +                                        MASTER_ABORT_MEM_PRIORITY);
> > +
> >      /* host bridge */
> >      QLIST_INIT(&bus->child);
> >  
> > diff --git a/include/hw/pci/pci_bus.h b/include/hw/pci/pci_bus.h
> > index 9df1788..2ad5edb 100644
> > --- a/include/hw/pci/pci_bus.h
> > +++ b/include/hw/pci/pci_bus.h
> > @@ -23,6 +23,7 @@ struct PCIBus {
> >      PCIDevice *parent_dev;
> >      MemoryRegion *address_space_mem;
> >      MemoryRegion *address_space_io;
> > +    MemoryRegion master_abort_mem;
> >  
> >      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