Re: [XEN PATCH v2 5/5] xen/arm: ffa: support notification

[Julien Grall <julien@xxxxxxx>]

Hi Bertrand,

On 23/04/2024 16:12, Bertrand Marquis wrote:
> Hi Julien,
>
> > On 22 Apr 2024, at 13:40, Julien Grall <julien@xxxxxxx> wrote:
> >
> > Hi Jens,
> >
> > This is not a full review of the code. I will let Bertrand doing it.
> >
> > On 22/04/2024 08:37, Jens Wiklander wrote:
> > > +void ffa_notif_init(void)
> > > +{
> > > +    const struct arm_smccc_1_2_regs arg = {
> > > +        .a0 = FFA_FEATURES,
> > > +        .a1 = FFA_FEATURE_SCHEDULE_RECV_INTR,
> > > +    };
> > > +    struct arm_smccc_1_2_regs resp;
> > > +    unsigned int irq;
> > > +    int ret;
> > > +
> > > +    arm_smccc_1_2_smc(&arg, &resp);
> > > +    if ( resp.a0 != FFA_SUCCESS_32 )
> > > +        return;
> > > +
> > > +    irq = resp.a2;
> > > +    if ( irq >= NR_GIC_SGI )
> > > +        irq_set_type(irq, IRQ_TYPE_EDGE_RISING);
> > > +    ret = request_irq(irq, 0, notif_irq_handler, "FF-A notif", NULL);
> > If I am not mistaken, ffa_notif_init() is only called once on the boot CPU. 
> > However, request_irq() needs to be called on every CPU so the callback is 
> > registered every where and the interrupt enabled.
> >
> > I know the name of the function is rather confusing. So can you confirm this is 
> > what you expected?
> >
> > [...]
> >
> > > diff --git a/xen/arch/arm/tee/ffa_private.h b/xen/arch/arm/tee/ffa_private.h
> > > index 98236cbf14a3..ef8ffd4526bd 100644
> > > --- a/xen/arch/arm/tee/ffa_private.h
> > > +++ b/xen/arch/arm/tee/ffa_private.h
> > > @@ -25,6 +25,7 @@
> > >   #define FFA_RET_DENIED                  -6
> > >   #define FFA_RET_RETRY                   -7
> > >   #define FFA_RET_ABORTED                 -8
> > > +#define FFA_RET_NO_DATA                 -9
> > >     /* FFA_VERSION helpers */
> > >   #define FFA_VERSION_MAJOR_SHIFT         16U
> > > @@ -97,6 +98,18 @@
> > >    */
> > >   #define FFA_MAX_SHM_COUNT               32
> > >   +/*
> > > + * TODO How to manage the available SGIs? SGI 8-15 seem to be entirely
> > > + * unused, but that may change.
> > Are the value below intended for the guests? If so, can they be moved in 
> > public/arch-arm.h along with the others guest interrupts?
> The values are to be used by the guest but they will discover them through the 
> FFA_FEATURES ABI so I do not think those
> should belong the public headers.
Sorry I should have been clearer. The values in the public headers are 
not meant for the guest. They are meant for a common understanding 
between the toolstack and Xen of the guest layout (memory + interrupts).
I know that some of the guests started to rely on it. But this is 
against our policy:
 * These are defined for consistency between the tools and the
 * hypervisor. Guests must not rely on these hardcoded values but
 * should instead use the FDT.

In this case, even if this is only used by Xen (today), I would argue 
they should defined at the same place because it is easier to understand 
the layout if it is in one place.
Cheers,

--
Julien Grall