Re: [Qemu-devel] [v6][PATCH 08/10] xen, gfx passthrough: support Intel IGD passthrough with VT-D

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Jan 19, 2015 at 05:28:41PM +0800, Tiejun Chen wrote:
> Some registers of Intel IGD are mapped in host bridge, so it needs to
> passthrough these registers of physical host bridge to guest because
> emulated host bridge in guest doesn't have these mappings.
> 
> Signed-off-by: Tiejun Chen <tiejun.chen@intel.com>
> Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
> ---
>  hw/pci-host/piix.c       |  3 ++
>  hw/xen/xen_pt.h          |  1 +
>  hw/xen/xen_pt_graphics.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 76 insertions(+)
> 
> diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
> index 1468961..0a5a4c7 100644
> --- a/hw/pci-host/piix.c
> +++ b/hw/pci-host/piix.c
> @@ -34,6 +34,7 @@
>  #include "sysemu/sysemu.h"
>  #include "hw/i386/ioapic.h"
>  #include "qapi/visitor.h"
> +#include "hw/xen/xen_pt.h"
>  
>  /*
>   * I440FX chipset data sheet.
> @@ -733,8 +734,10 @@ static void xen_igd_passthrough_i440fx_class_init(ObjectClass *klass,
>                                                    void *data)
>  {
>      DeviceClass *dc = DEVICE_CLASS(klass);
> +    PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
>  
>      dc->desc = "IGD PT XEN Host bridge";
> +    k->config_read = xen_igd_pci_read;
>  }
>  
>  static const TypeInfo xen_igd_passthrough_i440fx_info = {
> diff --git a/hw/xen/xen_pt.h b/hw/xen/xen_pt.h
> index 0aa5a93..94cde4a 100644
> --- a/hw/xen/xen_pt.h
> +++ b/hw/xen/xen_pt.h
> @@ -5,6 +5,7 @@
>  #include "hw/xen/xen_common.h"
>  #include "hw/pci/pci.h"
>  #include "xen-host-pci-device.h"
> +uint32_t xen_igd_pci_read(PCIDevice *pci_dev, uint32_t config_addr, int len);
>  
>  void xen_pt_log(const PCIDevice *d, const char *f, ...) GCC_FMT_ATTR(2, 3);
>  
> diff --git a/hw/xen/xen_pt_graphics.c b/hw/xen/xen_pt_graphics.c
> index 3232296..227089b 100644
> --- a/hw/xen/xen_pt_graphics.c
> +++ b/hw/xen/xen_pt_graphics.c
> @@ -4,6 +4,7 @@
>  #include "xen_pt.h"
>  #include "xen-host-pci-device.h"
>  #include "hw/xen/xen_backend.h"
> +#include "hw/pci/pci_bus.h"
>  
>  typedef struct VGARegion {
>      int type;           /* Memory or port I/O */
> @@ -188,3 +189,74 @@ int xen_pt_setup_vga(XenPCIPassthroughState *s, XenHostPCIDevice *dev)
>      cpu_physical_memory_rw(0xc0000, bios, bios_size, 1);
>      return 0;
>  }
> +
> +/*
> + * Currently we just pass this physical host bridge for IGD, 00:02.0.
> + *
> + * Here pci_dev is just that host bridge, so we have to get that real
> + * passthrough device by that given devfn to avoid other devices access.
> + */
> +static int is_igd_passthrough(PCIDevice *pci_dev)
> +{
> +    PCIDevice *f = pci_dev->bus->devices[PCI_DEVFN(2, 0)];
> +    if (pci_dev->bus->devices[PCI_DEVFN(2, 0)]) {
> +        XenPCIPassthroughState *s = DO_UPCAST(XenPCIPassthroughState, dev, f);
> +        return (is_igd_vga_passthrough(&s->real_device)
> +                    && (s->real_device.vendor_id == PCI_VENDOR_ID_INTEL));
> +    } else {
> +        return 0;
> +    }
> +}
> +
> +uint32_t xen_igd_pci_read(PCIDevice *pci_dev, uint32_t config_addr, int len)
> +{
> +    XenHostPCIDevice dev;
> +    uint32_t val;
> +    int r;
> +
> +    /* IGD read/write is through the host bridge.
> +     */
> +    assert(pci_dev->devfn == 0x00);
> +
> +    if (!is_igd_passthrough(pci_dev)) {
> +        goto read_default;
> +    }
> +
> +    /* Just work for the i915 driver. */
> +    switch (config_addr) {
> +    case 0x08:        /* revision id */
> +    case 0x2c:        /* sybsystem vendor id */
> +    case 0x2e:        /* sybsystem id */
> +    case 0x50:        /* SNB: processor graphics control register */
> +    case 0x52:        /* processor graphics control register */
> +    case 0xa0:        /* top of memory */

Is this host physical memory? If yes how can using it in guest work?

> +    case 0xa4:        /* SNB: graphics base of stolen memory */
> +    case 0xa8:        /* SNB: base of GTT stolen memory */

Same question for above two.

> +        break;
> +    default:
> +        /* Just gets the emulated values. */
> +        goto read_default;
> +    }
> +
> +    /* Host read */
> +    r = xen_host_pci_device_get(&dev, 0, 0, 0, 0);
> +    if (r) {
> +        goto err_out;
> +    }
> +
> +    r = xen_host_pci_get_block(&dev, config_addr, (uint8_t *)&val, len);
> +    if (r) {
> +        goto err_out;
> +    }
> +
> +    xen_host_pci_device_put(&dev);
> +
> +    return val;
> +
> +read_default:
> +    return pci_default_read_config(pci_dev, config_addr, len);
> +
> +err_out:
> +    XEN_PT_ERR(pci_dev, "Can't get pci_dev_host_bridge\n");
> +    return -1;
> +}

Do any of the above registers change with time?
Does it work if we just read them when device is created
and put in dev->config?

> -- 
> 1.9.1