[OpenBIOS] [PATCH] pci: enable io/memory unconditionally
Laurent Vivier
Laurent at Vivier.EU
Thu Dec 10 13:09:34 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 ?
>>
>> 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
--
--------------------- 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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