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

[Michael S. Tsirkin]

On Mon, Nov 17, 2014 at 10:47:56AM +0800, Chen, Tiejun wrote:
> 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 <address@hidden>
> >>---
> >>  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?

In xen_pt_initfn.
Just check the device and vendor ID against the table you have.


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

Yep.

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