[PATCH] irqchip/gic-v3: Work around insecure GIC integrations

[Marc Zyngier <maz@kernel.org>]

It appears that the relatively popular RK3399 SoC has been put together
using a large amount of illicit substances, as experiments reveal
that its integration of GIC500 exposes the *secure* programming
interface to non-secure.

This has some pretty bad effects on the way priorities are handled,
and results in a dead machine if booting with pseudo-NMI enabled
(irqchip.gicv3_pseudo_nmi=1) if the kernel contains 18fdb6348c480
("arm64: irqchip/gic-v3: Select priorities at boot time"), which
relies on the priorities being programmed using the NS view.

Let's restore some sanity by going one step further and disable
security altogether in this case. This is not any worse, and
puts us in a mode where priorities actually make some sense.

Huge thanks to Mark Kettenis who initially identified this issue
on OpenBSD, and to Chen-Yu Tsai who reported the problem in
Linux.

Fixes: 18fdb6348c480 ("arm64: irqchip/gic-v3: Select priorities at boot time")
Reported-by: Mark Kettenis <mark.kettenis@xs4all.nl>
Reported-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
---
 drivers/irqchip/irq-gic-v3.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index 34db379d066a5..79d8cc80693c3 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -161,7 +161,22 @@ static bool cpus_have_group0 __ro_after_init;
 
 static void __init gic_prio_init(void)
 {
-	cpus_have_security_disabled = gic_dist_security_disabled();
+	bool ds;
+
+	ds = gic_dist_security_disabled();
+	if (!ds) {
+		u32 val;
+
+		val = readl_relaxed(gic_data.dist_base + GICD_CTLR);
+		val |= GICD_CTLR_DS;
+		writel_relaxed(val, gic_data.dist_base + GICD_CTLR);
+
+		ds = gic_dist_security_disabled();
+		if (ds)
+			pr_warn("Broken GIC integration, security disabled");
+	}
+
+	cpus_have_security_disabled = ds;
 	cpus_have_group0 = gic_has_group0();
 
 	/*
-- 
2.39.2