Re: [Qemu-devel] [PATCH] hw/arm/virt: Add linux, pci-domain property

[Peter Maydell]

On 24 April 2018 at 15:12, Andrew Jones <address@hidden> wrote:
> On Mon, Apr 23, 2018 at 02:11:40PM +0100, Peter Maydell wrote:
>> On 23 April 2018 at 06:18, Jan Kiszka <address@hidden> wrote:
>> > From: Jan Kiszka <address@hidden>
>> >
>> > This allows to pin the host controller in the Linux PCI domain space.
>> > Linux requires that property to be available consistently or not at all,
>> > in which case the domain number becomes unstable on additions/removals.
>> > Adding it here won't make a difference in practice for most setups as we
>> > only expose one controller.
>> >
>> > However, enabling Jailhouse on top may introduce another controller, and
>> > that one would like to have stable address as well. So the property is
>> > needed for the first controller as well.
>>
>> Am I right in thinking that for ACPI the PCI domain number is
>> communicated via the _SEG method? If so, looks like we already
>> set that, and we set it to 0, which matches what we're doing here
>> in the DT, so that's good.
>
> _SEG and linux,pci-domain are similar in definition, but don't appear to
> be equivalent, as the same _SEG number is permitted across multiple host
> bridges, but linux,pci-domain must be unique for each host bridge. I
> think the (_SEG, _BBN) pair may form the equivalent. We also set _BBN
> to zero, so I think we're fine anyway.
>
>>
>> > Signed-off-by: Jan Kiszka <address@hidden>
>> > ---
>> >  hw/arm/virt.c | 1 +
>> >  1 file changed, 1 insertion(+)
>> >
>> > diff --git a/hw/arm/virt.c b/hw/arm/virt.c
>> > index 94dcb125d3..943371b75e 100644
>> > --- a/hw/arm/virt.c
>> > +++ b/hw/arm/virt.c
>> > @@ -1023,6 +1023,7 @@ static void create_pcie(const VirtMachineState *vms, 
>> > qemu_irq *pic)
>> >      qemu_fdt_setprop_string(vms->fdt, nodename, "device_type", "pci");
>> >      qemu_fdt_setprop_cell(vms->fdt, nodename, "#address-cells", 3);
>> >      qemu_fdt_setprop_cell(vms->fdt, nodename, "#size-cells", 2);
>> > +    qemu_fdt_setprop_cell(vms->fdt, nodename, "linux,pci-domain", 0);
>> >      qemu_fdt_setprop_cells(vms->fdt, nodename, "bus-range", 0,
>> >                             nr_pcie_buses - 1);
>> >      qemu_fdt_setprop(vms->fdt, nodename, "dma-coherent", NULL, 0);
>> > --
>>
>> Drew -- is minor changes to the DTC something we can do without
>> having to condition it on machine version? I forget...
>
> Yes, and even less minor changes than this one can be made to ACPI and DT
> generation, per the "if a firwmare update could change it, then don't
> worry about it" policy.

Cool; applied to target-arm.next, then.

-- PMM