linux-kernel - RE: [PATCH 1/2] hyperv-fb: add pci stub

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Date:	Tue, 8 Oct 2013 14:48:19 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Gerd Hoffmann <kraxel@...hat.com>
CC:	Haiyang Zhang <haiyangz@...rosoft.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	"open list:Hyper-V CORE AND..." <devel@...uxdriverproject.org>,
	"open list:FRAMEBUFFER LAYER" <linux-fbdev@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/2] hyperv-fb: add pci stub



> -----Original Message-----
> From: Gerd Hoffmann [mailto:kraxel@...hat.com]
> Sent: Tuesday, October 08, 2013 1:41 AM
> To: KY Srinivasan
> Cc: Haiyang Zhang; Jean-Christophe Plagniol-Villard; Tomi Valkeinen; open
> list:Hyper-V CORE AND...; open list:FRAMEBUFFER LAYER; open list
> Subject: Re: [PATCH 1/2] hyperv-fb: add pci stub
> 
> On Mo, 2013-10-07 at 17:12 +0000, KY Srinivasan wrote:
> >
> > > -----Original Message-----
> > > From: Gerd Hoffmann [mailto:kraxel@...hat.com]
> > > Sent: Sunday, October 06, 2013 11:51 PM
> > > To: KY Srinivasan
> > > Cc: Haiyang Zhang; Jean-Christophe Plagniol-Villard; Tomi Valkeinen; open
> > > list:Hyper-V CORE AND...; open list:FRAMEBUFFER LAYER; open list
> > > Subject: Re: [PATCH 1/2] hyperv-fb: add pci stub
> > >
> > > On Mi, 2013-10-02 at 14:29 +0000, KY Srinivasan wrote:
> > > >
> > > > > This patch adds a pci stub driver to hyper-fb.  The hyperv framebuffer
> > > > > driver will bind to the pci device then, so linux kernel and userspace
> > > > > know there is a proper kernel driver for the device active.  lspci shows
> > > > > this for example:
> > >
> > > > Gerd,
> > > >
> > > > Thanks for doing this. This certainly will address some of the issues that are
> > > reported. I do have a question though - how would this work if we don't have
> PCI
> > > bus in the guest.
> > >
> > > The hyperv framebuffer driver wouldn't work in the first place then as
> > > it looks up the framebuffer address in pci config space (see hvfb_getmem
> > > function).
> >
> > We are going to fix this as we move this code to run on our UEFI firmware.
> 
> Hmm, windows server 2012 seems to have no option to enable uefi.  So I
> guess this is still in development?  How this is going to look like?

This feature is there in WS2012 R2
> 
> Probably you are going for pure uefi firmware, without csm, to be able
> to leave all the legacy bios stuff behind in uefi mode.  Therefore no
> vesa bios support.  efi drivers for vmbus network/storage/display/input
> in the firmware.  No legacy ide/vga pci devices.  Correct?
> 
Something on these lines.

> The linux kernel will come up with efifb then, switching over to
> hyperv-fb once the driver is loaded.  The hyperv-fb pci stub driver will
> not bind to the hyperv vga pci device if it isn't present in the guest.
> hyperv-fb will load just fine nevertheless (once hvfb_getmem is fixed to
> not depend on the pci device config space).  The pci stub added by the
> patch and the vmbus driver in hyperv-fb are completely independent.

Ok; thanks.

K. Y