Re: [Xen-devel] [PATCH v2 3/3] xen/arm: vpsci: Move PSCI function dispatching from vsmc.c to vpsci.c

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 02/06/2018 03:28 PM, Volodymyr Babchuk wrote:
> Hi Julien,
>
> On 06.02.18 16:45, Julien Grall wrote:
>
> [...]
> > > > > > +/*
> > > > > > + * PSCI 0.2 or later calls. It will return false if the function 
> > > > > > ID is
> > > > > > + * not handled.
> > > > > > + */
> > > > > > +bool do_vpsci_0_2_call(struct cpu_user_regs *regs, uint32_t fid)
> > > > > > +{
> > > > > > +    /*
> > > > > > +     * /!\ VPSCI_NR_FUNCS (in asm-arm/vpsci.h) should be updated 
> > > > > > when
> > > > > > +     * adding/removing a function
> > > > > > +     */
> > > > > Should we also update revision of SSSC interface as well? SMCCC 
> > > > > requires this.
> > > > Meh, you can't rely on the SSSC revision most of the time as the 
> > > > version for PSCI is done through PSCI_get_version. I can add a 
> > > > comment if you want.
> > > Yes, I agree with you. But section 5.4 of SMCCC 1.0 applies to SSSC 
> > > as well. So you can write something like "ARM SMCCC requires that 
> > > SSSC revision and function call count should be updated every time 
> > > you add or remove a function"
> > Usually we update versioning number only once per release. I would 
> > follow the same approach for this one. So I would suggest
> It is not stated clearly in SMCCC, but I've got a felling that revision 
> belongs not to product version, but to SMC interface version. So I see 
> no reason to change revision, if there was no changes to interface itself.
> I'm okay witch changing revision only one time per release, but only
> if there was changes to PSCI interface. On other hand, person
> responsible for release need to track if there was any changes in PSCI
> and act accordingly. This is not very convenient.
> So, I would prefer to change revision in the same patch (or patch 
> series) which alters the interface.
At the end of the day this is closely tie to product revision. A new 
revision may produce change in the implementation and therefore the 
version will be bumped. But there are always exception when you do a 
release just for bug fix.
This is the same for Xen, we only change interface version if something 
major as changed. If nothing, then the version stays the same.
> > "VPSCI_NR_FUNCS (in asm-arm/vpsci.h) should be updated when adding 
> > removing a function. SSCCC_SMCCC_*_REVISION should be updated once per 
> > Xen release".
> And who will be responsible for this?
The first patch modifying the SMCCC implementation after the tree is 
re-opened. This is how we deal the rest of the versions in Xen, and it 
works.
Cheers,

--
Julien Grall

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