Messages in this thread Patch in this message | | | Date | Mon, 2 Oct 2023 18:24:11 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH 1/2] arm64: smp: Fix pseudo NMI issues w/ broken Mediatek FW |
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On Mon, Oct 02, 2023 at 09:45:29AM -0700, Douglas Anderson wrote: > Some mediatek devices have the property > "mediatek,broken-save-restore-fw" in their GIC. This means that, > although the hardware supports pseudo-NMI, the firmware has a bug > that blocks enabling it. When we're in this state, > system_uses_irq_prio_masking() will return true but we'll fail to > actually enable the IRQ in the GIC. > > Let's make the code handle this. We'll detect that we failed to > request an IPI as NMI and fallback to requesting it normally. Though > we expect that either all of our requests will fail or all will > succeed, it's just as cheap to keep a per-IPI bitmap and that keeps us > robust. > > Fixes: 331a1b3a836c ("arm64: smp: Add arch support for backtrace using pseudo-NMI") > Reported-by: Chen-Yu Tsai <wenst@chromium.org> > Closes: https://issuetracker.google.com/issues/197061987#comment68 > Signed-off-by: Douglas Anderson <dianders@chromium.org> > --- > > arch/arm64/kernel/smp.c | 19 ++++++++++++------- > 1 file changed, 12 insertions(+), 7 deletions(-)
I'm not too keen on falling back here when we have no idea why the request failed.
I'd prefer if we could check the `supports_pseudo_nmis` static key directly to account for the case of broken FW, e.g. as below.
Mark.
---->8---- From 72fdec05c64a74f21871b44c7c760bbe07cac044 Mon Sep 17 00:00:00 2001 From: Mark Rutland <mark.rutland@arm.com> Date: Mon, 2 Oct 2023 18:00:36 +0100 Subject: [PATCH] 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:
44bd78dd2b8897f5 ("irqchip/gic-v3: Disable pseudo NMIs on Mediatek devices w/ firmware issues")
We did not take this problem into account in commit:
331a1b3a836c0f38 ("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: 331a1b3a836c0f38 ("arm64: smp: Add arch support for backtrace using pseudo-NMI") Reported-by: Chen-Yu Tsai <wenst@chromium.org> Closes: https://issuetracker.google.com/issues/197061987#comment68 Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Douglas Anderson <dianders@chromium.org> Cc: Marc Zyngier <maz@kernel.org> --- arch/arm64/kernel/smp.c | 5 ++++- drivers/irqchip/irq-gic-v3.c | 2 +- 2 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index 814d9aa93b21b..061c69160f90f 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -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) { diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c index 787ccc880b22d..737da1b9aabf2 100644 --- a/drivers/irqchip/irq-gic-v3.c +++ b/drivers/irqchip/irq-gic-v3.c @@ -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); -- 2.30.2
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