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Re: [Qemu-devel] [QEMU][RFC PATCH 4/6] xen-pci: Register PCI in Xen
From: |
Stefano Stabellini |
Subject: |
Re: [Qemu-devel] [QEMU][RFC PATCH 4/6] xen-pci: Register PCI in Xen |
Date: |
Mon, 26 Mar 2012 14:56:44 +0100 |
User-agent: |
Alpine 2.00 (DEB 1167 2008-08-23) |
On Mon, 26 Mar 2012, Avi Kivity wrote:
> > > What about if two BARs (from different devices) are configured for the
> > > same address ranges?
> >
> > I think that it should have the same chance of happening as if there was
> > just one QEMU, because from the guest OS and firmware POV the emulated
> > hardware is the same. In any case Xen would return an error and QEMU can
> > either exit or try to cope with it.
>
> How can qemu cope? In a normal situation it's aware of all the devices,
> here it's not aware of any device (except the one it is managing).
>
> You're trying to convert a hierarchical problem into a flat one with no
> communication. What happens if one of the devices is a PCI-PCI bridge
> and it turns off its PCI window? The devices behind it should no longer
> respond, yet they know nothing about it.
>
> I think you need to preserve the hierarchy. The host-pci bridge needs
> to talk to devices behind it, (as does a pci-pci bridge).
PCI bridges are a problem, in fact I was thinking to just assume that
there are no PCI Bridges with PCI devices behind them other than the
Host PCI Bridge for now.
There is going to be a need for some kind of communication between the
multiple QEMU instances, for example for ACPI power state changes and
PCI Bridges, like you wrote. So I think that at some point we'll need to
introduce a type of message that originates from one of the QEMU
instances (the first one especially) and goes to all the others.
It should probably be relayed by the hypervisor.
- Re: [Qemu-devel] [QEMU][RFC PATCH 1/6] option: Add -xen-dmid, (continued)
- [Qemu-devel] [QEMU][RFC PATCH 4/6] xen-pci: Register PCI in Xen, Julien Grall, 2012/03/22
- Re: [Qemu-devel] [QEMU][RFC PATCH 4/6] xen-pci: Register PCI in Xen, Jan Kiszka, 2012/03/22
- Re: [Qemu-devel] [QEMU][RFC PATCH 4/6] xen-pci: Register PCI in Xen, Anthony Liguori, 2012/03/22
- Re: [Qemu-devel] [QEMU][RFC PATCH 4/6] xen-pci: Register PCI in Xen, Stefano Stabellini, 2012/03/23
- Re: [Qemu-devel] [QEMU][RFC PATCH 4/6] xen-pci: Register PCI in Xen, Avi Kivity, 2012/03/25
- Re: [Qemu-devel] [QEMU][RFC PATCH 4/6] xen-pci: Register PCI in Xen, Stefano Stabellini, 2012/03/26
- Re: [Qemu-devel] [QEMU][RFC PATCH 4/6] xen-pci: Register PCI in Xen, Avi Kivity, 2012/03/26
- Re: [Qemu-devel] [QEMU][RFC PATCH 4/6] xen-pci: Register PCI in Xen, Stefano Stabellini, 2012/03/26
- Re: [Qemu-devel] [QEMU][RFC PATCH 4/6] xen-pci: Register PCI in Xen, Avi Kivity, 2012/03/26
- Re: [Qemu-devel] [QEMU][RFC PATCH 4/6] xen-pci: Register PCI in Xen,
Stefano Stabellini <=
[Qemu-devel] [QEMU][RFC PATCH 2/6] xen: Add functions to register PCI and IO in Xen, Julien Grall, 2012/03/22
[Qemu-devel] [QEMU][RFC PATCH 5/6] xen-io: Handle the new ioreq type IOREQ_TYPE_PCI_CONFIG, Julien Grall, 2012/03/22