Re: [Qemu-devel] [RFC][PATCH 2/2] xen:i386:pc_piix: create isa bridge specific to IGD passthrough

["Chen, Tiejun" <tiejun.chen@intel.com>]

On 2014/11/5 22:09, Michael S. Tsirkin wrote:
> On Wed, Nov 05, 2014 at 03:22:59PM +0800, Tiejun Chen wrote:
>> Currently IGD drivers always need to access PCH by 1f.0, and
>> PCH vendor/device id is used to identify the card.
>>
>> Signed-off-by: Tiejun Chen <tiejun.chen@intel.com>
>> ---
>>   hw/i386/pc_piix.c | 28 +++++++++++++++++++++++++++-
>>   1 file changed, 27 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
>> index b559181..b19c7a9 100644
>> --- a/hw/i386/pc_piix.c
>> +++ b/hw/i386/pc_piix.c
>> @@ -50,7 +50,7 @@
>>   #include "cpu.h"
>>   #include "qemu/error-report.h"
>>   #ifdef CONFIG_XEN
>> -#  include <xen/hvm/hvm_info_table.h>
>> +#include <xen/hvm/hvm_info_table.h>
>>   #endif
>>
>>   #define MAX_IDE_BUS 2
>> @@ -452,6 +452,31 @@ static void pc_init_isa(MachineState *machine)
>>   }
>>
>>   #ifdef CONFIG_XEN
>> +static void xen_igd_passthrough_isa_bridge_create(PCIBus *bus)
>> +{
>> +    struct PCIDevice *dev;
>> +    Error *local_err = NULL;
>> +    uint16_t device_id = 0xffff;
>> +
>> +    /* Currently IGD drivers always need to access PCH by 1f.0. */
>> +    dev = pci_create_simple(bus, PCI_DEVFN(0x1f, 0),
>> +                            "xen-igd-passthrough-isa-bridge");
>> +
>> +    /* Identify PCH card with its own real vendor/device ids.
>> +     * Here that vendor id is always PCI_VENDOR_ID_INTEL.
>> +     */
>> +    if (dev) {
>> +        device_id = object_property_get_int(OBJECT(dev), "device-id",
>> +                                            &local_err);
>> +        if (!local_err && device_id != 0xffff) {
>> +            pci_config_set_device_id(dev->config, device_id);
>> +            return;
>> +        }
>> +    }
>> +
>> +    fprintf(stderr, "xen set xen-igd-passthrough-isa-bridge failed\n");
>> +}
>> +
>>   static void pc_xen_hvm_init(MachineState *machine)
>>   {
>>       PCIBus *bus;
>> @@ -461,6 +486,7 @@ static void pc_xen_hvm_init(MachineState *machine)
>>       bus = pci_find_primary_bus();
>>       if (bus != NULL) {
>>           pci_create_simple(bus, -1, "xen-platform");
>> +        xen_igd_passthrough_isa_bridge_create(bus);
>>       }
>>   }
>>   #endif
>
> Can't we defer this step until the GPU is added?

Sounds great but I can't figure out where we can to do this exactly.

> This way there won't be need to poke at host device
> directly, you could get all info from dev->config
> of the host device.

As I understand We have two steps here:

#1 At first I have to write something to check if we're registering 
00:02.0 & IGD, right? But where? While registering each pci device?

#2 Then if that condition is matched, we register this ISA bridge on its 
associated bus.

Thanks
Tiejun

> Additionally the correct bridge would be initialized automatically.
>
>
>> --
>> 1.9.1
>