Hi Florian,

On Tue, 19 May 2020 10:50:46 -0700
Florian Fainelli [off-list ref] wrote:

On 5/19/2020 9:17 AM, Marc Zyngier wrote:

quoted

For as long as SMP ARM has existed, IPIs have been handled as
something special. The arch code and the interrupt controller exchange
a couple of hooks (one to generate an IPI, another to handle it).

Although this is perfectly manageable, it prevents the use of features
that we could use if IPIs were Linux IRQs (such as pseudo-NMIs). It
also means that each interrupt controller driver has to follow an
architecture-specific interface instead of just implementing the base
irqchip functionnalities. The arch code also duplicates a number of
things that the core irq code already does (such as calling
set_irq_regs(), irq_enter()...).

This series tries to remedy this on arm/arm64 by offering a new
registration interface where the irqchip gives the arch code a range
of interrupts to use for IPIs. The arch code requests these as normal
interrupts.

The bulk of the work is at the interrupt controller level, where all 3
irqchips used on arm64 get converted.

Finally, the arm64 code drops the legacy registration interface. The
same thing could be done on 32bit as well once the two remaining
irqchips using that interface get converted.

There is probably more that could be done: statistics are still
architecture-private code, for example, and no attempt is made to
solve that (apart from hidding the IRQs from /proc/interrupt).

This has been tested on a bunch of 32 and 64bit guests.  

Does this patch series change your position on this patch series

https://lore.kernel.org/linux-arm-kernel/20191023000547.7831-3-f.fainelli@gmail.com/T/ (local)

or is this still a no-no?

I don't think this series changes anything. There is no easy way to
reserve SGIs in a way that would work for all combination of OS and FW,
and the prospect of sending SGIs between S and NS has already been
dubious (yes, the GIC architecture allows it, but it has been written
by people who have never designed any large piece of SW).

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

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