Re: [Qemu-devel] [SeaBIOS] [PATCH v3] hw/pci: reserve IO and mem for pci express downstream ports with no devices attached

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

On Mon, Jun 23, 2014 at 06:29:51PM +0300, Marcel Apfelbaum wrote:
> Commit c6e298e1f12e0f4ca02b6da5e42919ae055f6830
>     hw/pci: reserve IO and mem for pci-2-pci bridges with no devices attached
> 
> introduced support for hot-plugging devices behind pci-2-pci bridges.
> Extend hotplug support also for pci express downstream ports.
> 
> Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>


Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

Gerd, is there a plan to do a release for QEMU 2.1?
It would be nice to have this patch there.

Thanks,

> ---
> v2 -> v3:
>  Addressed Michael S. Tsirkin comments:
>  - Refactored pci_bus_hotplug_support function.
>  - Removed PCI_EXP_FLAGS_TYPE_SHIFT macro.
> 
> v1 -> v2:
>  Wrong prefix on first patch.
> 
>  src/fw/pciinit.c | 34 ++++++++++++++++++++++++++++++++--
>  1 file changed, 32 insertions(+), 2 deletions(-)
> 
> diff --git a/src/fw/pciinit.c b/src/fw/pciinit.c
> index 0ad548f..fd5dfb9 100644
> --- a/src/fw/pciinit.c
> +++ b/src/fw/pciinit.c
> @@ -636,6 +636,36 @@ pci_region_create_entry(struct pci_bus *bus, struct pci_device *dev,
>      return entry;
>  }
>  
> +static int pci_bus_hotplug_support(struct pci_bus *bus)
> +{
> +    u8 pcie_cap = pci_find_capability(bus->bus_dev, PCI_CAP_ID_EXP);
> +    u8 shpc_cap;
> +
> +    if (pcie_cap) {
> +        u16 pcie_flags = pci_config_readw(bus->bus_dev->bdf,
> +                                          pcie_cap + PCI_EXP_FLAGS);
> +        u8 port_type = ((pcie_flags & PCI_EXP_FLAGS_TYPE) >>
> +                       (__builtin_ffs(PCI_EXP_FLAGS_TYPE) - 1));
> +        u8 downstream_port = (port_type == PCI_EXP_TYPE_DOWNSTREAM) ||
> +                             (port_type == PCI_EXP_TYPE_ROOT_PORT);
> +        /*
> +         * PCI Express SPEC, 7.8.2:
> +         *   Slot Implemented – When Set, this bit indicates that the Link
> +         *   HwInit associated with this Port is connected to a slot (as
> +         *   compared to being connected to a system-integrated device or
> +         *   being disabled).
> +         *   This bit is valid for Downstream Ports. This bit is undefined
> +         *   for Upstream Ports.
> +         */
> +        u16 slot_implemented = pcie_flags & PCI_EXP_FLAGS_SLOT;
> +
> +        return downstream_port && slot_implemented;
> +    }
> +
> +    shpc_cap = pci_find_capability(bus->bus_dev, PCI_CAP_ID_SHPC);
> +    return !!shpc_cap;
> +}
> +
>  static int pci_bios_check_devices(struct pci_bus *busses)
>  {
>      dprintf(1, "PCI: check devices\n");
> @@ -678,7 +708,7 @@ static int pci_bios_check_devices(struct pci_bus *busses)
>              continue;
>          struct pci_bus *parent = &busses[pci_bdf_to_bus(s->bus_dev->bdf)];
>          int type;
> -        u8 shpc_cap = pci_find_capability(s->bus_dev, PCI_CAP_ID_SHPC);
> +        int hotplug_support = pci_bus_hotplug_support(s);
>          for (type = 0; type < PCI_REGION_TYPE_COUNT; type++) {
>              u64 align = (type == PCI_REGION_TYPE_IO) ?
>                  PCI_BRIDGE_IO_MIN : PCI_BRIDGE_MEM_MIN;
> @@ -687,7 +717,7 @@ static int pci_bios_check_devices(struct pci_bus *busses)
>              if (pci_region_align(&s->r[type]) > align)
>                   align = pci_region_align(&s->r[type]);
>              u64 sum = pci_region_sum(&s->r[type]);
> -            if (!sum && shpc_cap)
> +            if (!sum && hotplug_support)
>                  sum = align; /* reserve min size for hot-plug */
>              u64 size = ALIGN(sum, align);
>              int is64 = pci_bios_bridge_region_is64(&s->r[type],
> -- 
> 1.8.3.1