[PATCH 5.10 057/236] irqchip/gic-v3: Fix priority comparison when non-secure priorities are used

Greg Kroah-Hartman
2021-09-13T13:35:38Z

From: Chen-Yu Tsai <wenst@chromium.org>

[ Upstream commit 8d474deaba2c4dd33a5e2f5be82e6798ffa6b8a5 ]

When non-secure priorities are used, compared to the raw priority set,
the value read back from RPR is also right-shifted by one and the
highest bit set.

Add a macro to do the modifications to the raw priority when doing the
comparison against the RPR value. This corrects the pseudo-NMI behavior
when non-secure priorities in the GIC are used. Tested on 5.10 with
the "IPI as pseudo-NMI" series [1] applied on MT8195.

[1] https://lore.kernel.org/linux-arm-kernel/1604317487-14543-1-git-send-email-sumit.garg@linaro.org/

Fixes: 336780590990 ("irqchip/gic-v3: Support pseudo-NMIs when SCR_EL3.FIQ == 0")
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
[maz: Added comment contributed by Alex]
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210811171505.1502090-1-wenst@chromium.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/irqchip/irq-gic-v3.c | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index 1005b182bab4..1bdb7acf445f 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -100,6 +100,27 @@ EXPORT_SYMBOL(gic_pmr_sync);
DEFINE_STATIC_KEY_FALSE(gic_nonsecure_priorities);
EXPORT_SYMBOL(gic_nonsecure_priorities);

+/*
+ * When the Non-secure world has access to group 0 interrupts (as a
+ * consequence of SCR_EL3.FIQ == 0), reading the ICC_RPR_EL1 register will
+ * return the Distributor's view of the interrupt priority.
+ *
+ * When GIC security is enabled (GICD_CTLR.DS == 0), the interrupt priority
+ * written by software is moved to the Non-secure range by the Distributor.
+ *
+ * If both are true (which is when gic_nonsecure_priorities gets enabled),
+ * we need to shift down the priority programmed by software to match it
+ * against the value returned by ICC_RPR_EL1.
+ */
+#define GICD_INT_RPR_PRI(priority) \
+ ({ \
+ u32 __priority = (priority); \
+ if (static_branch_unlikely(&gic_nonsecure_priorities)) \
+ __priority = 0x80 | (__priority >> 1); \
+ \
+ __priority; \
+ })
+
/* ppi_nmi_refs[n] == number of cpus having ppi[n + 16] set as NMI */
static refcount_t *ppi_nmi_refs;

@@ -687,7 +708,7 @@ static asmlinkage void __exception_irq_entry gic_handle_irq(struct pt_regs *regs
return;

if (gic_supports_nmi() &&
- unlikely(gic_read_rpr() == GICD_INT_NMI_PRI)) {
+ unlikely(gic_read_rpr() == GICD_INT_RPR_PRI(GICD_INT_NMI_PRI))) {
gic_handle_nmi(irqnr, regs);
return;
}
--
2.30.2