Re: [PATCH v4] vfio/pci: Propagate ACPI notifications to user-space via eventfd
On Wed, 7 Jun 2023 22:22:12 +0200
Grzegorz Jaszczyk <jaz(a)semihalf.com> wrote:
> >
> > Can we drop the NTFY and just use VFIO_PCI_ACPI_IRQ_INDEX?
>
> ACPI_IRQ at first glance could be confused with SCI, which is e.g.
> registered as "acpi" irq seen in /proc/interrupts, maybe it is worth
> keeping NTFY here to emphasise the "Notify" part?
Please let me know if you prefer VFIO_PCI_ACPI_IRQ_INDEX or
VFIO_PCI_ACPI_NTFY_IRQ_INDEX taking into account the above.
This is a device level ACPI interrupt, so it doesn't seem like it would
be confused with SCI. What other ACPI related interrupts would a
device have? I'm still partial to dropping the NTFY but if you're
attached to it, let's not abbreviate it, make it NOTIFY and do the same
for function names.
...
> > > + } else if (flags & VFIO_IRQ_SET_DATA_BOOL)
{
> > > + u32 notification_val;
> > > +
> > > + if (!count)
> > > + return -EINVAL;
> > > +
> > > + notification_val = *(u32 *)data;
> >
> > DATA_BOOL is defined as a u8, and of course also as a bool, so we
> > expect only zero/non-zero. I think a valid interpretation would be any
> > non-zero value generates a device check notification value.
>
> Maybe it would be helpful and ease testing if we could use u8 as a
> notification value placeholder so it would be more flexible?
> Notification values from 0x80 to 0xBF are device-specific, 0xC0 and
> above are reserved for definition by hardware vendors for hardware
> specific notifications and BTW in practice I didn't see notification
> values that do not fit in u8 but even if exist we can limit to u8 and
> gain some flexibility anyway. Please let me know what you think.
Does the above seem ok for you?
The data type is only a u8 for practicality, it's still labeled as a
bool which suggests it's interpreted as either zero or non-zero. We
also need to reconcile DATA_NONE, which should trigger the interrupt,
but with an implicit notification value. I see the utility in what
you're proposing, but it logically implies an extension of the SET_IRQS
ioctl for a new data type which has hardly any practical value. Thanks,
Alex