Re: [Qemu-devel] [PATCH RFC] Implement GIC-500 from GICv3 family for arm64

[Shlomo Pongratz]

On 10 آذار, 2015 ص 03:18, Shannon Zhao wrote:
> On 2015/3/9 22:41, address@hidden wrote:
> > From: Shlomo Pongratz <address@hidden>
> >
> > This patch is a first step toward 128 cores support for arm64.
> >
> > At first only 64 cores are supported for two reasons:
> > First the largest integer type has the size of 64 bits and modifying
> > essential data structures in order to support 128 cores will require
> > the usage of bitops.
> > Second currently the Linux (kernel) can be configured to support
> > up to 64 cores thus there is no urgency with 128 cores support.
> >
> > Things left to do:
> >
> > Currently the booting Linux may got stuck. The probability of getting stuck
> > increases with the number of cores. I'll appreciate core review.
> >
> > There is a need to support flexible clusters size. The GIC-500 can support
> > up to 128 cores, up to 32 clusters and up to 8 cores is a cluster.
> > So for example, if one wishes to have 16 cores, the options are:
> > 2 clusters of 8 cores each, 4 clusters with 4 cores each
> > Currently only the first option is supported.
> > There is an issue of passing clock affinity to via the dtb. In the dtb
> >
> > interrupt section there are only 24 bit left to affinity since the
> > variable is a 32 bit entity and 8 bits are reserved for flags.
> > See Documentation/devicetree/bindings/arm/arch_timer.txt.
> > Note that this issue is not seems to be critical as when checking
> > /proc/irq/3/smp_affinity with 32 cores all 32 bits are one.
> >
> > The last issue is to add support for 128 cores. This requires the usage
> > of bitops and currently can be tested up to 64 cores.
> >
> > Signed-off-by: Shlomo Pongratz <address@hidden>
> > ---
> >   hw/arm/Makefile.objs               |    2 +-
> >   hw/arm/virtv2.c                    |  774 +++++++++++++++++
> Hi,
>
> I think here you want to introduce GICv3 in this patch. So is this necessary to
> add a new virtv2 machine? And the codes of this machine mostly are same with 
> virt.
>
> Maybe we can add a parameter such as -GICv3 for machine virt to choose GICv3 
> for it
> and choose GICv2 without this parameter. Then we can reuse more codes.
Hi Shannon,

Using a parameter and configuring the virtual machine makes the core
unreadable.
There are to many if then...else statements.

Best regards.
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