Re: [Xen-devel] [PATCH 3/3] xen/arm: vpsci: Move PSCI function dispatching from vsmc.c to vpsci.c

[Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>]

Hi Julien,

On 30.01.18 20:01, Julien Grall wrote:
> On 26/01/18 18:27, Volodymyr Babchuk wrote:
> > Hi,
> Hi Volodymyr,
>
> > On 26.01.18 20:15, Julien Grall wrote:
> > > Hi,
> > >
> > > On 26/01/18 18:09, Volodymyr Babchuk wrote:
> > > > On 24.01.18 20:34, Julien Grall wrote:
> > > > > -    case PSCI_0_2_FN32(AFFINITY_INFO):
> > > > > -    case PSCI_0_2_FN64(AFFINITY_INFO):
> > > > > +    switch ( fid )
> > > > >       {
> > > > > -        register_t taff = PSCI_ARG(regs, 1);
> > > > > -        uint32_t laff = PSCI_ARG32(regs, 2);
> > > > > -
> > > > > -        perfc_incr(vpsci_cpu_affinity_info);
> > > > > -        PSCI_SET_RESULT(regs, do_psci_0_2_affinity_info(taff, laff));
> > > > > -        return true;
> > > > > -    }
> > > > > -
> > > > >       case ARM_SMCCC_FUNC_CALL_COUNT(STANDARD):
> > > > >           return fill_function_call_count(regs, 
> > > > > SSSC_SMCCC_FUNCTION_COUNT);
> > > > Now definition SSSC_SMCCC_FUNCTION_COUNT depends on code in vscpi.c.
> > > > Maybe it is time to introduce function get_psci_0_2_fn_count() and 
> > > > use it there, what do you think?
> > > Definitely not a function. It is a static number. But I can think of 
> > > separate the call count.
> > Yep, separate call count for vPSCI and for SSSC itself would be a good 
> > thing.
> Looking a bit more into it, this will not make a real improvement. This 
> will be equally difficult to remember to update the call count.
Nevertheless, I think that it is right thing to hold call count in the
same file, where calls are implemented. This increases chances that call 
count will be held in sync.
> Also, based on the recent SMCCC update (2.1.5 [1]):
> "The General Service Queries for SMCCC call ranges are described in 
> SMCCC section 6.2. These functions are not always well suited to 
> firmware that is integrated with multiple sub-services being combined 
> into one service range. For example, PSCI and SDEI in the Standard 
> Service range. In particular, the ‘call count’ and ‘revision’ functions 
> do not provide useful information to the caller when multiple functions 
> are provided. As a result, these are not widely used to identify 
> firmware services."
> So I would not worry that much if the function count is not sync in the 
> future. BTW, it is already wrong in Xen 4.10. For standard service, we 
> don't implement 13 but 52.
2.1.5 deprecates general service queries in SMCCC 1.1. So, either we 
upgradeSMCCC in Xen to 1.1 or we should be conform with SMCCC 1.0 and 
should return right number of functions, including changes in Xen 4.10 
that you mentioned.
BTW, personally I'm not happy with call UID and call version 
deprecation. This makes impossible dynamic discovery of TEE, which was 
used in my TEE mediator patch series.

> Cheers,
>
> [1] 
> https://developer.arm.com/-/media/developer/pdf/ARM%20DEN%200070A%20Firmware%20interfaces%20for%20mitigating%20CVE-2017-5715_V1.0.pdf?revision=d20d1476-b770-4739-aebe-2d3147788e3f&la=en 
>
> I don't expect PSCI to be
There is some text missing. Are you wanted to add something?

--
Volodymyr Babchuk

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