Re: [Qemu-devel] [PATCH v4 2/8] pc: move igd support code to igd.c

From: "Tian, Kevin" <kevin.tian@intel.com>
To: Gerd Hoffmann <kraxel@redhat.com>
Cc: "igvt-g@ml01.01.org" <igvt-g@ml01.01.org>,
	"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Stefano Stabellini <stefano.stabellini@eu.citrix.com>,
	"Kay, Allen M" <allen.m.kay@intel.com>,
	"open list:All	patches CC here" <qemu-devel@nongnu.org>,
	Alex Williamson <alex.williamson@redhat.com>
Subject: Re: [Qemu-devel] [PATCH v4 2/8] pc: move igd support code to igd.c
Date: Thu, 10 Mar 2016 05:56:24 +0000	[thread overview]
Message-ID: <AADFC41AFE54684AB9EE6CBC0274A5D15F7E261C@SHSMSX101.ccr.corp.intel.com> (raw)
In-Reply-To: <1457536096.676.57.camel@redhat.com>

> From: Gerd Hoffmann [mailto:kraxel@redhat.com]
> Sent: Wednesday, March 09, 2016 11:08 PM
> 
>   Hi,
> 
> > +/* Here we just expose minimal host bridge offset subset. */
> > +static const IGDHostInfo igd_host_bridge_infos[] = {
> > +    {0x08, 2},  /* revision id */
> > +    {0x2c, 2},  /* sybsystem vendor id */
> > +    {0x2e, 2},  /* sybsystem id */
> 
> Can anyone clarify where this comes from?

Add Allen who is the original author.

> 
> 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 ...

It's possible that original list may become more than what current
driver requires...

> 
> > +    {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.
> 

Yes.

Thanks
Kevin