diff mbox

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

Message ID 1501964858-5159-5-git-send-email-zuban32s@gmail.com
State New
Headers show

Commit Message

Aleksandr Bezzubikov Aug. 5, 2017, 8:27 p.m. UTC
To enable hotplugging of a newly created pcie-pci-bridge,
we need to tell firmware (SeaBIOS in this case) 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 <zuban32s@gmail.com>
---
 hw/pci-bridge/gen_pcie_root_port.c | 33 +++++++++++++++++++++++++++++++++
 include/hw/pci/pcie_port.h         |  1 +
 2 files changed, 34 insertions(+)

Comments

Marcel Apfelbaum Aug. 7, 2017, 4:48 p.m. UTC | #1
On 05/08/2017 23:27, Aleksandr Bezzubikov wrote:
> To enable hotplugging of a newly created pcie-pci-bridge,
> we need to tell firmware (SeaBIOS in this case) 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 <zuban32s@gmail.com>
> ---
>   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);
> +
> +    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);
> 

Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>

Thanks,
Marcel
Michael S. Tsirkin Aug. 8, 2017, 7:54 p.m. UTC | #2
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?

> 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 <zuban32s@gmail.com>
> ---
>  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.

> +
> +    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 Aug. 8, 2017, 8:10 p.m. UTC | #3
2017-08-08 22:54 GMT+03:00 Michael S. Tsirkin <mst@redhat.com>:
> 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 <zuban32s@gmail.com>
>> ---
>>  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
Michael S. Tsirkin Aug. 8, 2017, 8:15 p.m. UTC | #4
On Tue, Aug 08, 2017 at 11:10:58PM +0300, Aleksandr Bezzubikov wrote:
> 2017-08-08 22:54 GMT+03:00 Michael S. Tsirkin <mst@redhat.com>:
> > 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.

So "e.g. SeaBIOS" would be more appropriate then.


> >> 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 <zuban32s@gmail.com>
> >> ---
> >>  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.

Any guest-visible behaviour change across the migration boundary
is prohibited. In this case, any code that walks a capability list
while you migrate will end up in the wrong place in config space.


> >> +
> >> +    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
diff mbox

Patch

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);
+
+    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);