Re: [Qemu-devel] [PATCH v3 4/5] hw/pci: add QEMU-specific PCI capability to Generic PCI Express Root Port

[Marcel Apfelbaum <marcel@redhat.com>]

On 29/07/2017 2:37, Aleksandr Bezzubikov wrote:
> From: Aleksandr Bezzubikov <abezzubikov@ispras.ru>
> 
> To enable hotplugging of a newly created pcie-pci-bridge,
> we need to tell firmware (SeaBIOS in this case)

Not only SeaBIOS, also OVMF - so all guest firmware

  to reserve
> additional buses for pcie-root-port, that allows us to
> hotplug pcie-pci-bridge into this root port.
> The number of buses to reserve is provided to the device via a corresponding
> property, and to the firmware via new PCI capability.
> The property's default value is 0 to keep default behavior unchanged.
> 
> Signed-off-by: Aleksandr Bezzubikov <zuban32s@gmail.com>
> ---
>   hw/pci-bridge/gen_pcie_root_port.c | 23 +++++++++++++++++++++++
>   hw/pci-bridge/pcie_root_port.c     |  2 +-
>   include/hw/pci/pcie_port.h         |  2 ++
>   3 files changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/pci-bridge/gen_pcie_root_port.c b/hw/pci-bridge/gen_pcie_root_port.c
> index cb694d6..da3caa1 100644
> --- a/hw/pci-bridge/gen_pcie_root_port.c
> +++ b/hw/pci-bridge/gen_pcie_root_port.c
> @@ -16,6 +16,8 @@
>   #include "hw/pci/pcie_port.h"
>   
>   #define TYPE_GEN_PCIE_ROOT_PORT                "pcie-root-port"
> +#define GEN_PCIE_ROOT_PORT(obj) \
> +        OBJECT_CHECK(GenPCIERootPort, (obj), TYPE_GEN_PCIE_ROOT_PORT)
>   
>   #define GEN_PCIE_ROOT_PORT_AER_OFFSET           0x100
>   #define GEN_PCIE_ROOT_PORT_MSIX_NR_VECTOR       1
> @@ -26,6 +28,9 @@ typedef struct GenPCIERootPort {
>       /*< public >*/
>   
>       bool migrate_msix;
> +
> +    /* additional buses to reserve on firmware init */
> +    uint8_t bus_reserve;
>   } GenPCIERootPort;
>   
>   static uint8_t gen_rp_aer_vector(const PCIDevice *d)
> @@ -60,6 +65,21 @@ static bool gen_rp_test_migrate_msix(void *opaque, int version_id)
>       return rp->migrate_msix;
>   }
>   
> +static void gen_rp_realize(PCIDevice *d, Error **errp)
> +{
> +    rp_realize(d, errp);
> +    PCIESlot *s = PCIE_SLOT(d);
> +    GenPCIERootPort *grp = GEN_PCIE_ROOT_PORT(d);
> +
> +    int rc = pci_bridge_qemu_cap_init(d, 0, grp->bus_reserve, 0, 0, 0, errp);
> +    if (rc < 0) {
> +        pcie_chassis_del_slot(s);
> +        pcie_cap_exit(d);
> +        gen_rp_interrupts_uninit(d);
> +        pci_bridge_exitfn(d);
> +    }
> +}
> +
>   static const VMStateDescription vmstate_rp_dev = {
>       .name = "pcie-root-port",
>       .version_id = 1,
> @@ -78,6 +98,7 @@ static const VMStateDescription vmstate_rp_dev = {
>   
>   static Property gen_rp_props[] = {
>       DEFINE_PROP_BOOL("x-migrate-msix", GenPCIERootPort, migrate_msix, true),
> +    DEFINE_PROP_UINT8("bus-reserve", GenPCIERootPort, bus_reserve, 0),
>       DEFINE_PROP_END_OF_LIST()
>   };
>   
> @@ -89,6 +110,8 @@ static void gen_rp_dev_class_init(ObjectClass *klass, void *data)
>   
>       k->vendor_id = PCI_VENDOR_ID_REDHAT;
>       k->device_id = PCI_DEVICE_ID_REDHAT_PCIE_RP;
> +    k->realize = gen_rp_realize;
> +
>       dc->desc = "PCI Express Root Port";
>       dc->vmsd = &vmstate_rp_dev;
>       dc->props = gen_rp_props;
> diff --git a/hw/pci-bridge/pcie_root_port.c b/hw/pci-bridge/pcie_root_port.c
> index 4d588cb..2f3bcb1 100644
> --- a/hw/pci-bridge/pcie_root_port.c
> +++ b/hw/pci-bridge/pcie_root_port.c
> @@ -52,7 +52,7 @@ static void rp_reset(DeviceState *qdev)
>       pci_bridge_disable_base_limit(d);
>   }
>   
> -static void rp_realize(PCIDevice *d, Error **errp)
> +void rp_realize(PCIDevice *d, Error **errp)
>   {
>       PCIEPort *p = PCIE_PORT(d);
>       PCIESlot *s = PCIE_SLOT(d);
> diff --git a/include/hw/pci/pcie_port.h b/include/hw/pci/pcie_port.h
> index 1333266..febd96a 100644
> --- a/include/hw/pci/pcie_port.h
> +++ b/include/hw/pci/pcie_port.h
> @@ -63,6 +63,8 @@ void pcie_chassis_del_slot(PCIESlot *s);
>   #define PCIE_ROOT_PORT_GET_CLASS(obj) \
>        OBJECT_GET_CLASS(PCIERootPortClass, (obj), TYPE_PCIE_ROOT_PORT)
>   
> +void rp_realize(PCIDevice *d, Error **errp);

This is not how QEMU re-uses parent's realize function.
You can grep for "parent_realize" in the project, it
goes something like this:
  1. You add  "DeviceRealize parent_realize" to GenPCIERootPort class.
  2. In class_init you save parent's realize and replace it with
     your own:
       grpc->parent_realize = dc->realize;
       dc->realize = gen_rp_realize;
  3. In gen_rp_realize call first parent_realize:
       rpc->parent_realize(dev, errp);
       - your code here -
       if (err)
           rpc-> exit()

Thanks,
Marcel

> +
>   typedef struct PCIERootPortClass {
>       PCIDeviceClass parent_class;
>   
>