Re: [OpenBIOS] [PATCH] pci: enable io/memory unconditionally

[Laurent Vivier]

> On Thu, Dec 10, 2009 at 01:20:23AM +0100, Laurent Vivier wrote:
> > Le mercredi 09 décembre 2009 à 17:53 +0200, Michael S. Tsirkin a écrit :
> > > VGA adapters need to claim memory and i/o
> > > transactions even if they do not have any
> > > i/o or memory bars. E.g. PCI spec, page 297,
> > > gives an example of such a device:
> > > Programming interface 0000 0000b
> > > VGA-compatible controller. Memory
> > > addresses 0A 0000h through 0B
> > > FFFFh. I/O addresses 3B0h to 3BBh
> > > and 3C0h to 3DFh and all aliases of
> > > these addresses.
> > >
> > > While bios could check for these devices and special-case them, it is
> > > easier to fix this by enabling i/o and memory space unconditionally:
> > > devices that do not support it will just ignore this setting.
> > >
> > > Signed-off-by: Michael S. Tsirkin
> >
> > Applied, but could you give me an use case where previous behavior
> > breaks something ?
> >
> > Regards,
> > Laurent
>
> qemu uses openbios and implements cirrus vga emulation,
> which has this device class and no IO bars.

qemu-system-ppc doesn't support cirrus vga emulation (only vga emulation), moreover openbios is not able to manage cirrus vga card.

So why this modification is needed ?

(even if it is correct according to the specs, it's why I've applied it)

Regards,
Laurent

[PATCH] pci: enable io/memory unconditionally

[Michael S. Tsirkin]

On Thu, Dec 10, 2009 at 01:09:34PM +0100, Laurent Vivier wrote:
> > On Thu, Dec 10, 2009 at 01:20:23AM +0100, Laurent Vivier wrote:
> > > Le mercredi 09 décembre 2009 à 17:53 +0200, Michael S. Tsirkin a écrit :
> > > > VGA adapters need to claim memory and i/o
> > > > transactions even if they do not have any
> > > > i/o or memory bars. E.g. PCI spec, page 297,
> > > > gives an example of such a device:
> > > > Programming interface 0000 0000b
> > > > VGA-compatible controller. Memory
> > > > addresses 0A 0000h through 0B
> > > > FFFFh. I/O addresses 3B0h to 3BBh
> > > > and 3C0h to 3DFh and all aliases of
> > > > these addresses.
> > > >
> > > > While bios could check for these devices and special-case them, it is
> > > > easier to fix this by enabling i/o and memory space unconditionally:
> > > > devices that do not support it will just ignore this setting.
> > > >
> > > > Signed-off-by: Michael S. Tsirkin
> > >
> > > Applied, but could you give me an use case where previous behavior
> > > breaks something ?
> > >
> > > Regards,
> > > Laurent
> >
> > qemu uses openbios and implements cirrus vga emulation,
> > which has this device class and no IO bars.
>
> qemu-system-ppc doesn't support cirrus vga emulation (only vga emulation), moreover openbios is not able to manage cirrus vga card.

Maybe it will support it in the future :).
> So why this modification is needed ?
> (even if it is correct according to the specs, it's why I've applied it)

It's not fixing any breakage I have observed, if that's what you mean.
I found the issue in bochs bios and seabios with
cirrus vga emulation, so I thought I'd fix up openbios as well.
> Regards,
> Laurent
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