Re: [Xen-devel] [PATCH RFC] xen/arm : emulation of arm's psci v0.2 standard

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 06/19/2014 05:00 PM, Stefano Stabellini wrote:
> On Thu, 19 Jun 2014, Parth Dixit wrote:
>> From: parthd <parth.dixit@xxxxxxxxxx>
>>
>> Arm based virtual machines dom0/guest will request power related 
>> functionality
>> from xen through psci interface. This patch implements version 0.2 of
>> PSCI standard specified by arm for 64bit and 32 bit arm machines.
>>
>> Signed-off-by: Parth Dixit <parth.dixit@xxxxxxxxxx>
>> ---
>>  xen/arch/arm/domain_build.c     |  5 ++-
>>  xen/arch/arm/traps.c            | 56 ++++++++++++++++++++++--
>>  xen/arch/arm/vpsci.c            | 75 ++++++++++++++++++++++++++++++++
>>  xen/include/asm-arm/processor.h |  6 +++
>>  xen/include/asm-arm/psci.h      | 18 ++++++++
>>  xen/include/public/arch-arm.h   | 95 
>> +++++++++++++++++++++++++++++++++++++++--
>>  6 files changed, 246 insertions(+), 9 deletions(-)
>>
>> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
>> index c424793..ebd4170 100644
>> --- a/xen/arch/arm/domain_build.c
>> +++ b/xen/arch/arm/domain_build.c
>> @@ -388,6 +388,9 @@ static int make_hypervisor_node(struct domain *d,
>>  static int make_psci_node(void *fdt, const struct dt_device_node *parent)
>>  {
>>      int res;
>> +    const char compat[] =
>> +        "arm,psci-0.2""\0"
>> +        "arm,psci";
>>  
>>      DPRINT("Create PSCI node\n");
>>  
>> @@ -396,7 +399,7 @@ static int make_psci_node(void *fdt, const struct 
>> dt_device_node *parent)
>>      if ( res )
>>          return res;
>>  
>> -    res = fdt_property_string(fdt, "compatible", "arm,psci");
>> +    res = fdt_property(fdt, "compatible", compat, sizeof(compat));
>>      if ( res )
>>          return res;
>>  
> 
> Even though you are adding the psci-0.2 compatible string, I don't see
> the new PSCI_0_2_FN_* function numbers being exposed to the guest yet.

These function numbers are defined by the spec. There is no need to
expose to the guest.

IIRC, the DT binding for PSCI v0.2 only contain the method to call psci
and the compatible string.

>> +/* PSCI return values (inclusive of all PSCI versions) */
>> +#define PSCI_RET_SUCCESS                     0
>> +#define PSCI_RET_NOT_SUPPORTED                      -1
>> +#define PSCI_RET_INVALID_PARAMS                     -2
>> +#define PSCI_RET_DENIED                             -3
>> +#define PSCI_RET_ALREADY_ON                 -4
>> +#define PSCI_RET_ON_PENDING                 -5
>> +#define PSCI_RET_INTERNAL_FAILURE           -6
>> +#define PSCI_RET_NOT_PRESENT                        -7
>> +#define PSCI_RET_DISABLED                   -8
> 
> Be careful: at the moment the functions in vpsci.c return the error
> codes specified in xen/include/asm-arm/psci.h.
> We should define the PSCI return codes only in one place.

It looks like this has been cut & paste from Linux patch (see
http://www.spinics.net/lists/arm-kernel/msg319712.html).

But this should not be exposed to neither the toolstack nor the guest.

Regards,

-- 
Julien Grall

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