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

["Michael S. Tsirkin" <mst@xxxxxxxxxx>]

On Fri, Aug 22, 2014 at 09:06:20AM +0800, Chen, Tiejun wrote:
> On 2014/8/22 0:16, Konrad Rzeszutek Wilk wrote:
> >On Thu, Aug 21, 2014 at 09:28:28AM +0800, Tiejun Chen wrote:
> >>Currenjly this ISA bridge should be fixed at 1f.0, and pass the
> >
> >Currently
> 
> Fixed.
> 
> >
> >>real vendor/device ids as the driver expect.
> >
> >Could you add a bit more description to this patch please? Explain
> >the rationale, etc.
> 
> So rephrase as follows:
> 
> xen:i386:pc_piix: create isa bridge specific to IGD passthrough
> 
> Currently IGD drivers always need to access PCH by 1f.0,

OK

> and
> identify PCH type with its own real vendor/device ids. This type
> value help driver initialize correctly.

instead: PCH vendor/device id is used to identify the card.

> >>
> >>Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxx>
> >>---
> >>  hw/i386/pc_piix.c | 24 +++++++++++++++++++++++-
> >>  1 file changed, 23 insertions(+), 1 deletion(-)
> >>
> >>diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> >>index 7710724..b131fa3 100644
> >>--- a/hw/i386/pc_piix.c
> >>+++ b/hw/i386/pc_piix.c
> >>@@ -50,7 +50,8 @@
> >>  #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>
> >>+#include <hw/xen/xen-host-pci-device.h>
> >>  #endif
> >>
> >>  #define MAX_IDE_BUS 2
> >>@@ -463,6 +464,26 @@ static void pc_xen_hvm_init(MachineState *machine)
> >>      }
> >>  }
> >>
> >>+static void xen_igd_passthrough_isa_bridge_create(PCIBus *bus)
> >>+{
> >>+    struct PCIDevice *dev;
> >>+    XenHostPCIDevice hdev;
> >>+    int r = 0;
> >>+
> >>+    /* This shoudl be fixed at 1f.0 then pass vendor/device ids.
> >
> >should
> >
> >However I would remove the comment as it does not add anything extra
> >to the function. It is pretty clear what it is doing.
> >
> >What would help is if you said:
> >
> >Must be fixed at 1f.0 because .. bla blah
> 
> Like the patch description, so what about this,
> 
>     /* Currently IGD drivers always need to access PCH by 1f.0, and
>      * identify PCH type with its own real vendor/device ids.
>      */
> 
> Thanks
> Tiejun
> 
> >
> >>+     */
> >>+    dev = pci_create_simple(bus, PCI_DEVFN(0x1f, 0),
> >>+                            "xen-igd-passthrough-isa-bridge");
> >>+    if (dev) {
> >>+        r = xen_host_pci_device_get(&hdev, 0, 0, PCI_DEVFN(0x1f, 0), 0);
> >>+        if (!r) {
> >>+            pci_config_set_vendor_id(dev->config, hdev.vendor_id);
> >>+            pci_config_set_device_id(dev->config, hdev.device_id);

Can you, instead, implement the reverse logic, probing
the card and supplying the correct device id for PCH?

> >>+        } else
> >>+            fprintf(stderr, "xen set xen-igd-passthrough-isa-bridge 
> >>failed\n");
> >>+    }
> >>+}
> >>+
> >>  static void xen_igd_passthrough_pc_hvm_init(MachineState *machine)
> >>  {
> >>      PCIBus *bus;
> >>@@ -472,6 +493,7 @@ static void 
> >>xen_igd_passthrough_pc_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
> >>--
> >>1.9.1
> >>
> >>
> >>_______________________________________________
> >>Xen-devel mailing list
> >>Xen-devel@xxxxxxxxxxxxx
> >>http://lists.xen.org/xen-devel
> >

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