Commit a07a5941 authored by Mark Rutland's avatar Mark Rutland Committed by Catalin Marinas
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arm64: smp: avoid NMI IPIs with broken MediaTek FW 



Some MediaTek devices have broken firmware which corrupts some GICR
registers behind the back of the OS, and pseudo-NMIs cannot be used on
these devices. For more details see commit:

  44bd78dd ("irqchip/gic-v3: Disable pseudo NMIs on Mediatek devices w/ firmware issues")

We did not take this problem into account in commit:

  331a1b3a ("arm64: smp: Add arch support for backtrace using pseudo-NMI")

Since that commit arm64's SMP code will try to setup some IPIs as
pseudo-NMIs, even on systems with broken FW. The GICv3 code will
(rightly) reject attempts to request interrupts as pseudo-NMIs,
resulting in boot-time failures.

Avoid the problem by taking the broken FW into account when deciding to
request IPIs as pseudo-NMIs. The GICv3 driver maintains a static_key
named "supports_pseudo_nmis" which is false on systems with broken FW,
and we can consult this within ipi_should_be_nmi().

Fixes: 331a1b3a ("arm64: smp: Add arch support for backtrace using pseudo-NMI")
Reported-by: default avatarChen-Yu Tsai <wenst@chromium.org>
Closes: https://issuetracker.google.com/issues/197061987#comment68


Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Reviewed-by: default avatarDouglas Anderson <dianders@chromium.org>
Tested-by: default avatarDouglas Anderson <dianders@chromium.org>
Reviewed-by: default avatarMarc Zyngier <maz@kernel.org>
Tested-by: default avatarChen-Yu Tsai <wenst@chromium.org>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 62817d5b

arch/arm64/kernel/smp.c

+4 −1
Original line number Diff line number Diff line
@@ -964,7 +964,10 @@ static void smp_cross_call(const struct cpumask *target, unsigned int ipinr) 


static bool ipi_should_be_nmi(enum ipi_msg_type ipi)

{

	if (!system_uses_irq_prio_masking())

	DECLARE_STATIC_KEY_FALSE(supports_pseudo_nmis);



	if (!system_uses_irq_prio_masking() ||

	    !static_branch_likely(&supports_pseudo_nmis))

		return false;



	switch (ipi) {

drivers/irqchip/irq-gic-v3.c

+1 −1
Original line number Diff line number Diff line
@@ -106,7 +106,7 @@ static DEFINE_STATIC_KEY_TRUE(supports_deactivate_key); 
 * - Figure 4-7 Secure read of the priority field for a Non-secure Group 1

 *   interrupt.

 */

static DEFINE_STATIC_KEY_FALSE(supports_pseudo_nmis);

DEFINE_STATIC_KEY_FALSE(supports_pseudo_nmis);



DEFINE_STATIC_KEY_FALSE(gic_nonsecure_priorities);

EXPORT_SYMBOL(gic_nonsecure_priorities);