[OpenBIOS] [PATCH] pci: enable io/memory unconditionally
Michael S. Tsirkin
mst at redhat.com
Thu Dec 10 10:17:41 CET 2009
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 <mst at redhat.com>
> Applied, but could you give me an use case where previous behavior
> breaks something ?
qemu uses openbios and implements cirrus vga emulation,
which has this device class and no IO bars.
> --------------------- laurent at vivier.eu ----------------------
> "Tout ce qui est impossible reste à accomplir" Jules Verne
> "Things are only impossible until they're not" Jean-Luc Picard
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