From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gerd Hoffmann <kraxel@redhat.com>
Subject: Re: [PATCH v4 2/8] pc: move igd support code to igd.c
Date: Wed, 09 Mar 2016 16:08:16 +0100
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Cc: igvt-g@ml01.01.org, xen-devel@lists.xensource.com, "Michael S. Tsirkin" <mst@redhat.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, "open list:All
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  Hi,

> +/* Here we just expose minimal host bridge offset subset. */
> +static const IGDHostInfo igd_host_bridge_infos[] =3D {
> +    {0x08, 2},  /* revision id */
> +    {0x2c, 2},  /* sybsystem vendor id */
> +    {0x2e, 2},  /* sybsystem id */

Can anyone clarify where this comes from?

Setting the subsystem id without also setting the pci id looks wrong,
given that each pci id has its own subsystem id namespace.

Testing (with alex vfio patches) shows that dropping this seems to have
no bad effects.  Things are still working fine of we only set these ...

> +    {0x50, 2},  /* SNB: processor graphics control register */
> +    {0x52, 2},  /* processor graphics control register */
> +    {0xa4, 4},  /* SNB: graphics base of stolen memory */
> +    {0xa8, 4},  /* SNB: base of GTT stolen memory */

... gfx registers in host bridge pci config space.

thanks,
  Gerd