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Re: [Qemu-ppc] [Qemu-devel] [PATCH] PPC: fix PCI configuration space Mem

From: Mark Cave-Ayland
Subject: Re: [Qemu-ppc] [Qemu-devel] [PATCH] PPC: fix PCI configuration space MemoryRegions for grackle/uninorth
Date: Fri, 08 Nov 2013 22:18:34 +0000
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.12) Gecko/20130116 Icedove/10.0.12

On 08/11/13 03:20, Alexander Graf wrote:

On 11.10.2013, at 12:53, Mark Cave-Ayland<address@hidden>  wrote:

OpenBIOS prior to SVN r1225 had a horrible bug when accessing PCI
configuration space for PPC Mac architectures - instead of writing the PCI
configuration data value to the data register address, it would instead write
it to the data register address plus the PCI configuration address.

For this reason, the MemoryRegions for the PCI data register for
grackle/uninorth were extremely large in order to accomodate the entire PCI
configuration space being accessed during OpenBIOS PCI bus enumeration. Now
that the OpenBIOS images have been updated, reduce the MemoryRegion sizes down
to a single 32-bit register as intended.

Signed-off-by: Mark Cave-Ayland<address@hidden>
CC: Hervé Poussineau<address@hidden>
CC: Andreas Färber<address@hidden>
CC: Alexander Graf<address@hidden>

With this patch applied, mac99 emulation seems to break:



Hi Alex,

Thanks for the heads-up - with the information above I was able to reproduce this fairly easily. I had look at some of the uninorth drivers, and while it's not particularly apparent from Linux that the PCI configuration data is accessed via MMIO rather than ioport access, FreeBSD seems to suggest that this is the case: http://code.google.com/p/freebsd-head/source/browse/sys/powerpc/powermac/uninorth.c?spec=svnc6989e24706228678e454517dad4ad465a36e556&r=c6989e24706228678e454517dad4ad465a36e556#274.

The key is that the QEMU uninorth host bridge contains a hack to allow PCI configuration mechanism #1 as used by OpenBIOS to work at all (see unin_get_config_reg() in hw/pci-host/uninorth.c) which is why I didn't notice it in my OpenBIOS boot tests; and in fact, the name of the uninorth PCI configuration data MemoryRegions have a "-data" rather than a "-idx" suffix is also a big clue.

Hence please find a revised version of the patch which is unaltered for grackle, and only changes the MemoryRegion size for the PCI configuration address register for uninorth so that the PCI configuration data space is still accessible using MMIO. This resolves the issue for me, so if you're satisifed that it works for you then I'll post a revised version to the list.



Attachment: qemu-ppc-pci-fix.patch
Description: Text Data

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