Re: [Qemu-devel] [PATCH v4 4/5] hw/pci: add QEMU-specific PCI capability to the Generic PCI Express Root Port

[Aleksandr Bezzubikov]

2017-08-08 22:54 GMT+03:00 Michael S. Tsirkin <address@hidden>:
> On Sat, Aug 05, 2017 at 11:27:37PM +0300, Aleksandr Bezzubikov wrote:
>> To enable hotplugging of a newly created pcie-pci-bridge,
>> we need to tell firmware (SeaBIOS in this case)
>
> Why SeaBIOS is this case?
>

It is the default BIOS for QEMU and therefore it is the best place to
try out a new feature like this reservation cap.

>> to reserve
>> additional buses or IO/MEM/PREF space for pcie-root-port.
>> Additional bus reservation 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 properties' default value is -1 to keep default behavior unchanged.
>>
>> Signed-off-by: Aleksandr Bezzubikov <address@hidden>
>> ---
>>  hw/pci-bridge/gen_pcie_root_port.c | 33 +++++++++++++++++++++++++++++++++
>>  include/hw/pci/pcie_port.h         |  1 +
>>  2 files changed, 34 insertions(+)
>>
>> diff --git a/hw/pci-bridge/gen_pcie_root_port.c 
>> b/hw/pci-bridge/gen_pcie_root_port.c
>> index cb694d6..ff8d04c 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 +28,12 @@ typedef struct GenPCIERootPort {
>>      /*< public >*/
>>
>>      bool migrate_msix;
>> +
>> +    /* additional buses to reserve on firmware init */
>> +    uint32_t bus_reserve;
>> +    uint64_t io_reserve;
>> +    uint64_t mem_reserve;
>> +    uint64_t pref_reserve;
>>  } GenPCIERootPort;
>>
>>  static uint8_t gen_rp_aer_vector(const PCIDevice *d)
>> @@ -60,6 +68,23 @@ static bool gen_rp_test_migrate_msix(void *opaque, int 
>> version_id)
>>      return rp->migrate_msix;
>>  }
>>
>> +static void gen_rp_realize(DeviceState *dev, Error **errp)
>> +{
>> +    PCIDevice *d = PCI_DEVICE(dev);
>> +    GenPCIERootPort *grp = GEN_PCIE_ROOT_PORT(d);
>> +    PCIERootPortClass *rpc = PCIE_ROOT_PORT_GET_CLASS(d);
>> +
>> +    rpc->parent_realize(dev, errp);
>> +
>> +    int rc = pci_bridge_qemu_reserve_cap_init(d, 0, grp->bus_reserve,
>> +            grp->io_reserve, grp->mem_reserve, grp->pref_reserve, errp);
>
> You have to skip adding this capability by default to avoid
> breaking migration to/from old QEMU. A simple way to do this is
> to check whether any have been specified as != -1.
>

Agreed, I can't understand how the capability that is brand new
and unused by another code except mine can break migration.

>> +
>> +    if (rc < 0) {
>> +        rpc->parent_class.exit(d);
>> +        return;
>> +    }
>> +}
>> +
>>  static const VMStateDescription vmstate_rp_dev = {
>>      .name = "pcie-root-port",
>>      .version_id = 1,
>> @@ -78,6 +103,10 @@ static const VMStateDescription vmstate_rp_dev = {
>>
>>  static Property gen_rp_props[] = {
>>      DEFINE_PROP_BOOL("x-migrate-msix", GenPCIERootPort, migrate_msix, true),
>> +    DEFINE_PROP_UINT32("bus-reserve", GenPCIERootPort, bus_reserve, -1),
>> +    DEFINE_PROP_UINT64("io-reserve", GenPCIERootPort, io_reserve, -1),
>> +    DEFINE_PROP_UINT64("mem-reserve", GenPCIERootPort, mem_reserve, -1),
>> +    DEFINE_PROP_UINT64("pref-reserve", GenPCIERootPort, pref_reserve, -1),
>>      DEFINE_PROP_END_OF_LIST()
>>  };
>>
>> @@ -92,6 +121,10 @@ static void gen_rp_dev_class_init(ObjectClass *klass, 
>> void *data)
>>      dc->desc = "PCI Express Root Port";
>>      dc->vmsd = &vmstate_rp_dev;
>>      dc->props = gen_rp_props;
>> +
>> +    rpc->parent_realize = dc->realize;
>> +    dc->realize = gen_rp_realize;
>> +
>>      rpc->aer_vector = gen_rp_aer_vector;
>>      rpc->interrupts_init = gen_rp_interrupts_init;
>>      rpc->interrupts_uninit = gen_rp_interrupts_uninit;
>> diff --git a/include/hw/pci/pcie_port.h b/include/hw/pci/pcie_port.h
>> index 1333266..0736014 100644
>> --- a/include/hw/pci/pcie_port.h
>> +++ b/include/hw/pci/pcie_port.h
>> @@ -65,6 +65,7 @@ void pcie_chassis_del_slot(PCIESlot *s);
>>
>>  typedef struct PCIERootPortClass {
>>      PCIDeviceClass parent_class;
>> +    DeviceRealize parent_realize;
>>
>>      uint8_t (*aer_vector)(const PCIDevice *dev);
>>      int (*interrupts_init)(PCIDevice *dev, Error **errp);
>> --
>> 2.7.4



-- 
Aleksandr Bezzubikov