Re: [Xen-devel] [v5][PATCH 2/5] xen, gfx passthrough: create pseudo intel isa bridge

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

On 2014/6/25 14:45, Michael S. Tsirkin wrote:
> On Wed, Jun 25, 2014 at 10:17:18AM +0800, Tiejun Chen wrote:
> > ISA bridge is needed since Intel gfx drive will probe with Dev31:Fun0
> > to make graphics device passthrough work well for VMM, that only need
> > to expose this pseudo ISA bridge to let driver know the real hardware
> > underneath.
> >
> > The original patch is from Allen Kay <allen.m.kay@xxxxxxxxx>
> >
> > Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
> > Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxx>
> > Cc: Allen Kay <allen.m.kay@xxxxxxxxx>
> > ---
> > v5:
> >
> > * Don't set this ISA class property, instead, just fake this ISA bridge
> >    with 00:1f.0.
> >
> > v4:
> >
> > * Remove some unnecessary "return" in void foo().
> >
> > v3:
> >
> > * Fix some typos.
> > * Improve some return paths.
> >
> > v2:
> >
> > * Nothing is changed.
> >
> >   hw/xen/xen_pt_graphics.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 61 insertions(+)
> >
> > diff --git a/hw/xen/xen_pt_graphics.c b/hw/xen/xen_pt_graphics.c
> > index 461e526..974b7e9 100644
> > --- a/hw/xen/xen_pt_graphics.c
> > +++ b/hw/xen/xen_pt_graphics.c
> > @@ -230,3 +230,64 @@ out:
> >       g_free(bios);
> >       return rc;
> >   }
> > +
> > +static uint32_t isa_bridge_read_config(PCIDevice *d, uint32_t addr, int len)
> > +{
> > +    return pci_default_read_config(d, addr, len);
> > +}
> > +
> > +static void isa_bridge_write_config(PCIDevice *d, uint32_t addr, uint32_t v,
> > +                                    int len)
> > +{
> > +    pci_default_write_config(d, addr, v, len);
> > +}
> > +
> > +static void isa_bridge_class_init(ObjectClass *klass, void *data)
> > +{
> > +    PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
> > +
> > +    k->config_read = isa_bridge_read_config;
> > +    k->config_write = isa_bridge_write_config;
> > +};
> You don't need these stubs, just don't fill anything,
> pci core will use defaults then.
I guess these stubs are left to extend something in the future. But 
maybe we can remove them now.
> > +
> > +typedef struct {
> > +    PCIDevice dev;
> > +} ISABridgeState;
> > +
> Nor do you need an empty structure if it has no state.
>
> > +static TypeInfo isa_bridge_info = {
> > +    .name          = "pseudo-intel-pch-isa-bridge",
> > +    .parent        = TYPE_PCI_DEVICE,
> > +    .instance_size = sizeof(ISABridgeState),
> > +    .class_init = isa_bridge_class_init,
> > +};
> > +
> > +static void xen_pt_graphics_register_types(void)
> > +{
> > +    type_register_static(&isa_bridge_info);
> > +}
> > +
> > +type_init(xen_pt_graphics_register_types)
> > +
> > +static int create_pseudo_pch_isa_bridge(PCIBus *bus, XenHostPCIDevice *hdev)
> > +{
> > +    struct PCIDevice *dev;
> > +
> > +    char rid;
> > +
> > +    /* We havt to use a simple PCI device to fake this ISA bridge
> > +     * to avoid making some confusion to BIOS and ACPI.
> > +     */
> A typo and confusing wording above, I'm not really
> sure what this comment means.
> Maybe:
>
> /* Create a fake ISA bridge device at the location expected by guests. */
Good comments so thanks so much.

> > +    dev = pci_create(bus, PCI_DEVFN(0x1f, 0), "pseudo-intel-pch-isa-bridge");
> > +
> > +    qdev_init_nofail(&dev->qdev);
> > +
> > +    pci_config_set_vendor_id(dev->config, hdev->vendor_id);
> > +    pci_config_set_device_id(dev->config, hdev->device_id);
> > +
> > +    xen_host_pci_get_block(hdev, PCI_REVISION_ID, (uint8_t *)&rid, 1);
> Host PCI device is the VGA card?
This is a real ISA bridge.

> So why does it make sense to get it's vendor/device/revision and
> stick in the ISA bridge?
The Intel generation of integrated graphics needs to probe this ISA 
bridge to initialize the i915 driver properly.
Thanks
Tiejun

> Also change rid to uint8_t, you won't need to cast then.
>
> > +
> > +    pci_config_set_revision(dev->config, rid);
> > +
> > +    XEN_PT_LOG(dev, "The pseudo Intel PCH ISA bridge created.\n");
> > +    return 0;
> > +}
> > --
> > 1.9.1
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel