[irqchip: irq/irqchip-next] irqchip/gic-v3: Ensure pseudo-NMIs have an ISB between ack and handling

[irqchip-bot for Mark Rutland]

The following commit has been merged into the irq/irqchip-next branch of irqchip:

Commit-ID:     adf14453d2c037ab529040c1186ea32e277e783a
Gitweb:        https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms/adf14453d2c037ab529040c1186ea32e277e783a
Author:        Mark Rutland <mark.rutland@xxxxxxx>
AuthorDate:    Fri, 13 May 2022 14:30:36 +01:00
Committer:     Marc Zyngier <maz@xxxxxxxxxx>
CommitterDate: Sun, 15 May 2022 16:38:18 +01:00

irqchip/gic-v3: Ensure pseudo-NMIs have an ISB between ack and handling

There are cases where a context synchronization event is necessary
between an IRQ being raised and being handled, and there are races such
that we cannot rely upon the exception entry being subsequent to the
interrupt being raised.

We identified and fixes this for regular IRQs in commit:

  39a06b67c2c1256b ("irqchip/gic: Ensure we have an ISB between ack and ->handle_irq")

Unfortunately, we forgot to do the same for psuedo-NMIs when support for
those was added in commit:

  f32c926651dcd168 ("irqchip/gic-v3: Handle pseudo-NMIs")

Which means that when pseudo-NMIs are used for PMU support, we'll hit
the same problem.

Apply the same fix as for regular IRQs. Note that when EOI mode 1 is in
use, the call to gic_write_eoir() will provide an ISB.

Fixes: f32c926651dcd168 ("irqchip/gic-v3: Handle pseudo-NMIs")
Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Marc Zyngier <maz@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20220513133038.226182-2-mark.rutland@xxxxxxx
---
 drivers/irqchip/irq-gic-v3.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index b252d55..7305d84 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -654,6 +654,9 @@ static inline void gic_handle_nmi(u32 irqnr, struct pt_regs *regs)
 
 	if (static_branch_likely(&supports_deactivate_key))
 		gic_write_eoir(irqnr);
+	else
+		isb()
+
 	/*
 	 * Leave the PSR.I bit set to prevent other NMIs to be
 	 * received while handling this one.