Re: [Qemu-devel] [PATCH V8 RESEND 4/8] pci.c: Add pci_check_bar_overlap

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Mar 16, 2012 at 04:54:18PM +0000, Anthony PERARD wrote:
> From: Yuji Shimada <shimada-yxb@necst.nec.co.jp>
> 
> This function helps Xen PCI Passthrough device to check for overlap.
> 
> Signed-off-by: Yuji Shimada <shimada-yxb@necst.nec.co.jp>
> Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>

It seems that what's called for here really is
using the new memory region infrastructure.
That handles overlap etc nicely.

That said, I don't mind, but would prefer to
keep this mess outside the pci core. See below.

> ---
>  hw/pci.c |   50 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  hw/pci.h |    5 +++++
>  2 files changed, 55 insertions(+), 0 deletions(-)
> 
> diff --git a/hw/pci.c b/hw/pci.c
> index 38e1de5..f950b4e 100644
> --- a/hw/pci.c
> +++ b/hw/pci.c
> @@ -1992,6 +1992,56 @@ MemoryRegion *pci_address_space_io(PCIDevice *dev)
>      return dev->bus->address_space_io;
>  }
>  
> +/* This function

Comment blocks start with /* */

> checks if an io_region overlap an io_region from another

overlaps

> + * device.  The io_region to check is provide with (addr, size and type)

provided

> + * A callback can be provide and will be called for every region that is

provided

> + * overlapped.
> + * The return value indicate if the region is overlappsed */

indicates


> +bool pci_check_bar_overlap(PCIDevice *device,
> +                           pcibus_t addr, pcibus_t size, uint8_t type,
> +                           void (*c)(void *o, const PCIDevice *d, int index),
> +                           void *opaque)

IMO this is inlikely to be needed by anyone except Xen.
How about a generic pci_foreach_device and let Xen
implement the hacks internally.

> +{
> +    PCIBus *bus = device->bus;
> +    int i, j;
> +    bool rc = false;
> +
> +    for (i = 0; i < ARRAY_SIZE(bus->devices); i++) {
> +        PCIDevice *d = bus->devices[i];
> +        if (!d) {
> +            continue;
> +        }
> +
> +        if (d->devfn == device->devfn) {
> +            continue;
> +        }
> +
> +        /* xxx: This ignores bridges. */
> +        for (j = 0; j < PCI_NUM_REGIONS; j++) {
> +            PCIIORegion *r = &d->io_regions[j];
> +
> +            if (!r->size) {
> +                continue;
> +            }
> +            if ((type & PCI_BASE_ADDRESS_SPACE_IO)
> +                != (r->type & PCI_BASE_ADDRESS_SPACE_IO)) {
> +                continue;
> +            }
> +
> +            if (ranges_overlap(addr, size, r->addr, r->size)) {
> +                if (c) {
> +                    c(opaque, d, j);
> +                    rc = true;
> +                } else {
> +                    return true;
> +                }
> +            }
> +        }
> +    }
> +
> +    return rc;
> +}
> +
>  static void pci_device_class_init(ObjectClass *klass, void *data)
>  {
>      DeviceClass *k = DEVICE_CLASS(klass);
> diff --git a/hw/pci.h b/hw/pci.h
> index 4f19fdb..cbd04e1 100644
> --- a/hw/pci.h
> +++ b/hw/pci.h
> @@ -628,4 +628,9 @@ extern const VMStateDescription vmstate_pci_device;
>      .offset     = vmstate_offset_pointer(_state, _field, PCIDevice), \
>  }
>  
> +bool pci_check_bar_overlap(PCIDevice *dev,
> +                           pcibus_t addr, pcibus_t size, uint8_t type,
> +                           void (*c)(void *o, const PCIDevice *d, int index),
> +                           void *opaque);
> +
>  #endif
> -- 
> Anthony PERARD