Re: [Xen-devel] [RFC PATCH v2 03/26] ARM: GICv3 ITS: allocate device and collection table

[Julien Grall <julien.grall@xxxxxxx>]

Hello,

On 04/01/2017 22:47, Stefano Stabellini wrote:
> On Thu, 22 Dec 2016, Andre Przywara wrote:
> > Each ITS maps a pair of a DeviceID (usually the PCI b/d/f triplet) and
> > an EventID (the MSI payload or interrupt ID) to a pair of LPI number
> > and collection ID, which points to the target CPU.
> > This mapping is stored in the device and collection tables, which software
> > has to provide for the ITS to use.
> > Allocate the required memory and hand it the ITS.
> > The maximum number of devices is limited to a compile-time constant
> > exposed in Kconfig.
> >
> > Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
> > ---
> >  xen/arch/arm/Kconfig          |   6 +++
> >  xen/arch/arm/gic-its.c        | 114 ++++++++++++++++++++++++++++++++++++++++++
> >  xen/arch/arm/gic-v3.c         |   5 ++
> >  xen/include/asm-arm/bitops.h  |   1 +
> >  xen/include/asm-arm/gic-its.h |  51 ++++++++++++++++++-
> >  5 files changed, 176 insertions(+), 1 deletion(-)
> >
> > diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
> > index a7d941c..a369305 100644
> > --- a/xen/arch/arm/Kconfig
> > +++ b/xen/arch/arm/Kconfig
> > @@ -59,6 +59,12 @@ config MAX_HOST_LPI_BITS
> >            This can be overriden on the command line with the max_lpi_bits
> >            parameter.
> >
> > +config MAX_ITS_PCI_BUSSES
> > +        depends on HAS_ITS
> > +        int "Number of PCI busses the ITS supports (4)"
> > +        range 1 1024
> > +        default "4"
> Given that any kind of devices can be behind an ITS, including non-PCI
> devices, I think it is best to call this MAX_PHYS_ITS_DEVICES.
I don't think we should limit the number of devices supported at 
compilation time. We aim to have a single Xen binary running on any 
board. The best would be to guess the number at runtime, but I would be 
fine with a command line options.
Cheers,

--
Julien Grall

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