Re: [Xen-devel] [PATCH V6 03/10] xen/arm: Use the new functions for vCPUID/vaffinity transformation

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 05/06/2015 16:56, Ian Campbell wrote:
> On Mon, 2015-06-01 at 20:56 +0800, Chen Baozi wrote:
> > From: Chen Baozi <baozich@xxxxxxxxx>
> >
> > There are 3 places to change:
> >
> > * Initialise vMPIDR value in vcpu_initialise()
> > * Find the vCPU from vMPIDR affinity information when accessing GICD
> >    registers in vGIC
> > * Find the vCPU from vMPIDR affinity information when booting with vPSCI
> >    in vGIC
> >    - Also make the code for PSCI 0.1 use MPIDR-like value as the cpuid.
> Does this "- Also ..." not need to be done at the same time as the
> change to how we describe things in the FDT? Since that is where the
> guest gets the parameter from, isn't it?
Well, we only support 8 CPUs. So this changes will return the same value 
as before. It may be worth to mention it.
In another side, both PSCI 0.1 and PSCI 0.2 are modified to respect the 
MPIDR like within this patch. The working in the commit message may be 
misleading.
Somehow the code path slightly differ when the PSCI 0.2 for guest has 
been added. The spec says (PSCI 0.1 Section 6.3 (ARM DEN 0022A)):
"Ideally platform discovery mechanism such as firmware tables would be
used by secure firmware to describe the set of valid CPUIDs to the
hypervisor or Rich OS, if the former is not present. The hypervisor in
turn can create and supply virtual discovery mechanisms to its guests.""

I interpreted this as CPUID is equal to the "reg" register in DT (which 
is an MPIDR-like value).
FWIW, this is the interpretation made by Linux too.

Regards,

--
--
Julien Grall

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