Re: [Xen-devel] [PATCH v2 0/2] Support of RO MMCFG access for PVH/HVMlite dom0s

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 12/18/2015 09:16 AM, Jan Beulich wrote:
> > > > On 18.12.15 at 14:53, <boris.ostrovsky@xxxxxxxxxx> wrote:
> > On 12/18/2015 08:02 AM, Andrew Cooper wrote:
> > > On 18/12/15 10:11, Jan Beulich wrote:
> > > > > > > On 17.12.15 at 21:22, <boris.ostrovsky@xxxxxxxxxx> wrote:
> > > > > * Left non-MMCFG RO accesses unhandled (we havent't encountered those
> > accesses
> > > > >     yet with PVH dom0 and it's probably better to fault on them and
> > investigate
> > > > >     whether they are guest's issues).
> > > > I seriously question this being a good approach,
> > > I concur.  All accesses should be terminated somehow, even if this is
> > > the hypervisor dropping writes and completing reads with ~0's.
> > >
> > > This is the expected behaviour from the x86 architecture.
> > OK, I'll add that in.
> >
> > To answer Jan's question, I did try 'vga=keep' and that worked fine.
> Interesting. Does your system not load/use a DRM driver for the
> card? Or is the driver so minimalistic that no extended config
> space write ever occurs?
It does load the driver:

0b:00.0 VGA compatible controller: Matrox Graphics, Inc. MGA G200e 
[Pilot] ServerEngines (SEP1) (rev 04)
    Subsystem: Intel Corporation Device 0101
    Kernel driver in use: mgag200
..
root@ovs104> lsmod | grep mgag
mgag200                45056  1
ttm                    90112  1 mgag200
drm_kms_helper        122880  1 mgag200
drm                   335872  4 mgag200,ttm,drm_kms_helper
i2c_algo_bit           16384  2 igb,mgag200

but I don't know what it does to the config space. I configured my 
kernel for a fairly minimal configuration so perhaps I disabled 
something that limits what the driver does.
-boris

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