Re: [Qemu-devel] [PATCH] pci: Add generic PCI device option to disable 64bit MMIO BARs

[Alex Williamson <alex.williamson@redhat.com>]

On Wed, 2012-02-01 at 15:57 -0700, Alex Williamson wrote:
> As we start to enable 64bit I/O devices, there's a good chance
> we'll find bugs and compatibility issues.  This allows a user
> to toggle off (default on) 64bit PCI MMIO BARs, downgrading
> them to 32bit BARs.
> 
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
> 
> Should this be an "x-mem64" option implying that it's really
> only for debugging and may go away or could this have some
> longevity?
> 
>  hw/pci.c |   18 ++++++++++++++++++
>  hw/pci.h |    4 ++++
>  2 files changed, 22 insertions(+), 0 deletions(-)
> 
> diff --git a/hw/pci.c b/hw/pci.c
> index 57ec104..9afddb0 100644
> --- a/hw/pci.c
> +++ b/hw/pci.c
> @@ -63,6 +63,8 @@ struct BusInfo pci_bus_info = {
>                          QEMU_PCI_CAP_MULTIFUNCTION_BITNR, false),
>          DEFINE_PROP_BIT("command_serr_enable", PCIDevice, cap_present,
>                          QEMU_PCI_CAP_SERR_BITNR, true),
> +        DEFINE_PROP_BIT("mem64", PCIDevice, cap_present,
> +                        QEMU_PCI_CAP_MEM64_BITNR, true),
>          DEFINE_PROP_END_OF_LIST()
>      }
>  };
> @@ -957,6 +959,22 @@ void pci_register_bar(PCIDevice *pci_dev, int region_num,
>          exit(1);
>      }
>  
> +    if (!(type & PCI_BASE_ADDRESS_SPACE_IO)) {
> +        if (!(pci_dev->cap_present & QEMU_PCI_CAP_MEM64)) {
> +            type &= ~PCI_BASE_ADDRESS_MEM_TYPE_64;
> +        }
> +
> +        /* 32bit BARs are limited to 2GB */
> +        if (size >= 0x80000000U && !(type & PCI_BASE_ADDRESS_MEM_TYPE_64)) {

Oops, this should just be >, not >=.  I'll wait to see if this has any
legs before respinning.

> +            fprintf(stderr, "Device %04x:%02x:%02x.%x BAR %d is %ld "
> +                    "GB, 64bit memory type required\n",
> +                    pci_find_domain(pci_dev->bus), pci_bus_num(pci_dev->bus),
> +                    PCI_SLOT(pci_dev->devfn), PCI_FUNC(pci_dev->devfn),
> +                    region_num, (long)(size >> 30));
> +            exit(1);
> +        }
> +    }
> +
>      r = &pci_dev->io_regions[region_num];
>      r->addr = PCI_BAR_UNMAPPED;
>      r->size = size;
> diff --git a/hw/pci.h b/hw/pci.h
> index 4220151..17fd996 100644
> --- a/hw/pci.h
> +++ b/hw/pci.h
> @@ -126,6 +126,10 @@ enum {
>      /* command register SERR bit enabled */
>  #define QEMU_PCI_CAP_SERR_BITNR 4
>      QEMU_PCI_CAP_SERR = (1 << QEMU_PCI_CAP_SERR_BITNR),
> +
> +    /* expose 64bit MMIO BARs when available */
> +#define QEMU_PCI_CAP_MEM64_BITNR 5
> +    QEMU_PCI_CAP_MEM64 = (1 << QEMU_PCI_CAP_MEM64_BITNR),
>  };
>  
>  typedef int (*msix_mask_notifier_func)(PCIDevice *, unsigned vector,
>