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Date: Tue, 26 Nov 2013 15:11:01 +0100
From: Laszlo Ersek <lersek@redhat.com>
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Subject: Re: [Qemu-devel] [PULL for-1.8 1/2] pc: disable pci-info
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>, "Jordan Justen (Intel address)" <jordan.l.justen@intel.com>, qemu-devel@nongnu.org, Gerd Hoffmann <kraxel@redhat.com>, Anthony Liguori <aliguori@amazon.com>, Igor Mammedov <imammedo@redhat.com>

On 11/26/13 10:10, Michael S. Tsirkin wrote:

> seabios manages to enumerate PCI with information exported from qemu
> so why can't OVMF?

SeaBIOS and qemu duplicate logic (code) between each other.

src/fw/pciinit.c grabs RamSize over fw_cfg, and i440fx_mem_addr_setup()
sets "pcimem_start" to one of three values based on RamSize. (One of the
three is not explicit there, it's the build default 0xe0000000.)

The same code is visible in qemu in i440fx_init().

I duplicated the same logic in OVMF's PEI one week ago, and it solved
the problem. See the patch attached to
<http://thread.gmane.org/gmane.comp.bios.tianocore.devel/4881/focus=4995>.

But code/logic duplication is ugly, which is why I've been looking for a
better, dynamic solution ever since.

> I think it's down to other qemu bugs (such as _CRS not covering
> all of PCI memory), we shall just fix them.

I don't know how to fix them. I don't know how to enumerate all PCI
regions in use, plus all unassigned ranges, from below, like with a
MemoryListener.

If I understand correctly, Igor suggested to track devices as they map
their regions, but (again, if I understood correctly) you didn't seem to
like the idea.

Thanks
Laszlo