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Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root
From: |
Kevin O'Connor |
Subject: |
Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses. |
Date: |
Thu, 11 Jun 2015 15:24:27 -0400 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Thu, Jun 11, 2015 at 08:34:56PM +0200, Laszlo Ersek wrote:
> On 06/11/15 19:46, Marcel Apfelbaum wrote:
> > On 06/11/2015 07:54 PM, Kevin O'Connor wrote:
> >> On real machines, the firmware assigns the 4 - it's not a physical
> >> address; it's a logical address (like all bus numbers in PCI). The
> >> firmware might assign a totally different number on the next boot.
> > Now I am confused. Don't get me wrong, I am not an expert on fw, I hardly
> > try to understand it.
> >
> > I looked up a real hardware machine and it seemed to me that the extra
> > pci root numbers
> > are provided in the ACPI tables, meaning by the vendor, not the fw.
> > In this case QEMU is the vendor, i440fx is the machine, right?
> >
> > I am not aware that Seabios/OVMF are deciding the bus numbers for the
> > *PCI roots*.
> > They are doing it for the pci-2-pci bridges of course.
> > I saw that Seabios is trying to "guess" the root-buses by going over all
> > the 0-0xff range
> > and probing all the slots, looking for devices. So it expects the hw to
> > be hardwired regarding
> > PCI root buses.
>
> This is exactly how I understood it.
>
> We're not interested in placing such bus numbers in device paths that
> are assigned during PCI enumeration. (Like subordinate bus numbers.)
> We're talking about the root bus numbers.
>
> OVMF implements the same kind of probing that SeaBIOS does (based on
> natural language description from Michael and Marcel, not on the actual
> code). Devices on the root buses respond without any prior bus number
> assignments.
Alas, that is not correct. Coreboot supports several AMD boards that
have multiple southbridge chips which provide independent PCI root
buses. These chips have to be configured and assigned a bus number
prior to use (which coreboot does).
-Kevin
- [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Marcel Apfelbaum, 2015/06/11
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Laszlo Ersek, 2015/06/11
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Kevin O'Connor, 2015/06/11
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Marcel Apfelbaum, 2015/06/11
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Kevin O'Connor, 2015/06/11
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Marcel Apfelbaum, 2015/06/11
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Laszlo Ersek, 2015/06/11
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Kevin O'Connor, 2015/06/11
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Marcel Apfelbaum, 2015/06/11
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Laszlo Ersek, 2015/06/11
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses.,
Kevin O'Connor <=
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Laszlo Ersek, 2015/06/12
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Kevin O'Connor, 2015/06/12
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Laszlo Ersek, 2015/06/12
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Kevin O'Connor, 2015/06/12
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Laszlo Ersek, 2015/06/12
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Michael S. Tsirkin, 2015/06/14
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Kevin O'Connor, 2015/06/14
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Michael S. Tsirkin, 2015/06/14
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Kevin O'Connor, 2015/06/14
- Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses., Benjamin Herrenschmidt, 2015/06/14