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Re: [Qemu-ppc] [Qemu-devel] [PATCH 0/1] pci: allow 0 address for PCI IO/

From: Alexander Graf
Subject: Re: [Qemu-ppc] [Qemu-devel] [PATCH 0/1] pci: allow 0 address for PCI IO/MEM regions
Date: Tue, 13 Jan 2015 18:01:53 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.0

On 01/13/15 17:17, Michael S. Tsirkin wrote:
On Tue, Jan 13, 2015 at 05:54:46PM +0200, Michael S. Tsirkin wrote:
I think we already do this for PC:
        commit 83d08f2673504a299194dcac1657a13754b5932a
        Author: Michael S. Tsirkin <address@hidden>
        Date:   Tue Oct 29 13:57:34 2013 +0100

            pc: map PCI address space as catchall region for not mapped 

but we need to find and fix all other targets.
BTW this is very easy to test.
Add an unused device (like ivshmem) enable BAR, and set it to 0.
System should survive, as opposed to hanging.

But the big question is whether this is the right
thing to do for each platform.
For PIIX whatever is not system memory, is PCI.
But other boxes might have a different view of the matter.

Only few platforms have PCI mapped at 0, no? So in most cases you get windows that simply don't have overlapping at all.


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