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Re: [Qemu-devel] [SeaBIOS] [PATCH] hw/pci: reserve IO and mem for pci-2-
From: |
Marcel Apfelbaum |
Subject: |
Re: [Qemu-devel] [SeaBIOS] [PATCH] hw/pci: reserve IO and mem for pci-2-pci bridges with no devices attached |
Date: |
Mon, 07 Apr 2014 17:16:13 +0300 |
On Mon, 2014-04-07 at 17:09 +0300, Michael S. Tsirkin wrote:
> On Mon, Apr 07, 2014 at 04:51:54PM +0300, Marcel Apfelbaum wrote:
[...]
> > > > I don't think we'll need that for the SHPC bridge.
> > >
> > > Why not?
> > Because "has shpc" => not an PCIe port. (as far as I know)
> > Anyway, why have shpc capability but no I/O or mem to support it?
^^^
[...]
>
>
> AFAIK the spec does not list reset value for this register.
> IIRC QEMU resets both to 0.
Thanks, what do you think about the above ? ^^^
While I am not against it, it seems redundant.
It has shpc => it needs I/O or mem space.
Marcel
>
>
> > > - read back value
> > >
> > > value 0 means bridge does not support I/O.
> > >
> > >
> > > A similar trick should work for other optional resources.
> > >
> > >
> > > > For express it indeed makes sense to avoid claiming IO address space.
> > > > I'd try to find something more automatic though, where you don't need
> > > > some kind of "disable io for this express port" config option.
> > >
> > > Won't same trick as above work?
> > >
> > > > For express ports which can only have a single device underneath we can
> > > > check whenever we have a device and if one is present already don't
> > > > bother claiming extra resources for hotplug.
> > > >
> > > > > > + for (cap = pci_config_readb(pci->bdf, PCI_CAPABILITY_LIST);
> > > > > > cap;
> > > > > > + cap = pci_config_readb(pci->bdf, cap +
> > > > > > PCI_CAP_LIST_NEXT))
> > > > > > + if (pci_config_readb(pci->bdf, cap + PCI_CAP_LIST_ID) ==
> > > > > > cap_id)
> > > > > > + return cap;
> > > > >
> > > > > I would also limit this to 256 iterations, to make sure
> > > > > we dont' get into an infinite loop with a broken device.
> > > >
> > > > Good point.
> > > >
> > > > cheers,
> > > > Gerd
> > > >
> >
> >
- Re: [Qemu-devel] [SeaBIOS] [PATCH] hw/pci: reserve IO and mem for pci-2-pci bridges with no devices attached, (continued)
- Re: [Qemu-devel] [SeaBIOS] [PATCH] hw/pci: reserve IO and mem for pci-2-pci bridges with no devices attached, Gerd Hoffmann, 2014/04/07
- Re: [Qemu-devel] [SeaBIOS] [PATCH] hw/pci: reserve IO and mem for pci-2-pci bridges with no devices attached, Michael S. Tsirkin, 2014/04/07
- Re: [Qemu-devel] [SeaBIOS] [PATCH] hw/pci: reserve IO and mem for pci-2-pci bridges with no devices attached, Gerd Hoffmann, 2014/04/07
- Re: [Qemu-devel] [SeaBIOS] [PATCH] hw/pci: reserve IO and mem for pci-2-pci bridges with no devices attached, Marcel Apfelbaum, 2014/04/07
- Re: [Qemu-devel] [SeaBIOS] [PATCH] hw/pci: reserve IO and mem for pci-2-pci bridges with no devices attached, Michael S. Tsirkin, 2014/04/07
- Re: [Qemu-devel] [SeaBIOS] [PATCH] hw/pci: reserve IO and mem for pci-2-pci bridges with no devices attached, Marcel Apfelbaum, 2014/04/07
- Re: [Qemu-devel] [SeaBIOS] [PATCH] hw/pci: reserve IO and mem for pci-2-pci bridges with no devices attached, Marcel Apfelbaum, 2014/04/07
- Re: [Qemu-devel] [SeaBIOS] [PATCH] hw/pci: reserve IO and mem for pci-2-pci bridges with no devices attached, Michael S. Tsirkin, 2014/04/07
- Re: [Qemu-devel] [SeaBIOS] [PATCH] hw/pci: reserve IO and mem for pci-2-pci bridges with no devices attached,
Marcel Apfelbaum <=
- Re: [Qemu-devel] [SeaBIOS] [PATCH] hw/pci: reserve IO and mem for pci-2-pci bridges with no devices attached, Michael S. Tsirkin, 2014/04/07
- Re: [Qemu-devel] [SeaBIOS] [PATCH] hw/pci: reserve IO and mem for pci-2-pci bridges with no devices attached, Gerd Hoffmann, 2014/04/08
- Re: [Qemu-devel] [SeaBIOS] [PATCH] hw/pci: reserve IO and mem for pci-2-pci bridges with no devices attached, Michael S. Tsirkin, 2014/04/08