Re: [RFC PATCH 03/23] genirq: Introduce IRQF_DELIVER_AS_NMI

From: Julien Thierry
Date: Wed Jun 13 2018 - 05:37:08 EST

On 13/06/18 10:20, Thomas Gleixner wrote:
On Wed, 13 Jun 2018, Julien Thierry wrote:
On 13/06/18 09:34, Peter Zijlstra wrote:
On Tue, Jun 12, 2018 at 05:57:23PM -0700, Ricardo Neri wrote:
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 5426627..dbc5e02 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -61,6 +61,8 @@
* interrupt handler after suspending interrupts. For
* wakeup devices users need to implement wakeup
detection in
* their interrupt handlers.
+ * IRQF_DELIVER_AS_NMI - Configure interrupt to be delivered as
non-maskable, if
+ * supported by the chip.

NAK on the first 6 patches. You really _REALLY_ don't want to expose
NMIs to this level.

I've been working on something similar on arm64 side, and effectively the one
thing that might be common to arm64 and intel is the interface to set an
interrupt as NMI. So I guess it would be nice to agree on the right approach
for this.

The way I did it was by introducing a new irq_state and let the irqchip driver
handle most of the work (if it supports that state):

This has not been ACKed nor NAKed. So I am just asking whether this is a more
suitable approach, and if not, is there any suggestions on how to do this?

I really didn't pay attention to that as it's burried in the GIC/ARM series
which is usually Marc's playground.

Adding NMI delivery support at low level architecture irq chip level is
perfectly fine, but the exposure of that needs to be restricted very
much. Adding it to the generic interrupt control interfaces is not going to
happen. That's doomed to begin with and a complete abuse of the interface
as the handler can not ever be used for that.

Understood, however the need would be to provide a way for a driver to request an interrupt to be delivered as an NMI (if irqchip supports it).

But from your response this would be out of the question (in the interrupt/irq/irqchip definitions).

Or somehow the concerned irqchip informs the arch it supports NMI delivery and it is up to the interested drivers to query the arch whether NMI delivery is supported by the system?


Julien Thierry