From: Nicholas Piggin <npiggin@gmail.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: Ganesh Goudar <ganeshgr@linux.ibm.com>,
Nicholas Piggin <npiggin@gmail.com>
Subject: [PATCH 4/5] powerpc/64/interrupt: Reconcile soft-mask state in NMI and fix false BUG
Date: Tue, 5 Oct 2021 00:56:41 +1000 [thread overview]
Message-ID: <20211004145642.1331214-5-npiggin@gmail.com> (raw)
In-Reply-To: <20211004145642.1331214-1-npiggin@gmail.com>
If a NMI hits early in an interrupt handler before the irq soft-mask
state is reconciled, that can cause a false-positive BUG with a
CONFIG_PPC_IRQ_SOFT_MASK_DEBUG assertion.
Remove that assertion and instead check the case that if regs->msr has
EE clear, then regs->softe should be marked as disabled so the irq state
looks correct to NMI handlers, the same as how it's fixed up in the
case it was implicit soft-masked.
This doesn't fix a known problem -- the change that was fixed by commit
4ec5feec1ad02 ("powerpc/64s: Make NMI record implicitly soft-masked code
as irqs disabled") was the addition of a warning in the soft-nmi
watchdog interrupt which can never actually fire when MSR[EE]=0. However
it may be important if NMI handlers grow more code, and it's less
surprising to anything using 'regs' - (I tripped over this when working
in the area).
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
arch/powerpc/include/asm/interrupt.h | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
index 6b800d3e2681..b894b7169706 100644
--- a/arch/powerpc/include/asm/interrupt.h
+++ b/arch/powerpc/include/asm/interrupt.h
@@ -265,13 +265,16 @@ static inline void interrupt_nmi_enter_prepare(struct pt_regs *regs, struct inte
local_paca->irq_soft_mask = IRQS_ALL_DISABLED;
local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
- if (is_implicit_soft_masked(regs)) {
- // Adjust regs->softe soft implicit soft-mask, so
- // arch_irq_disabled_regs(regs) behaves as expected.
+ if (!(regs->msr & MSR_EE) || is_implicit_soft_masked(regs)) {
+ /*
+ * Adjust regs->softe to be soft-masked if it had not been
+ * reconcied (e.g., interrupt entry with MSR[EE]=0 but softe
+ * not yet set disabled), or if it was in an implicit soft
+ * masked state. This makes arch_irq_disabled_regs(regs)
+ * behave as expected.
+ */
regs->softe = IRQS_ALL_DISABLED;
}
- if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
- BUG_ON(!arch_irq_disabled_regs(regs) && !(regs->msr & MSR_EE));
/* Don't do any per-CPU operations until interrupt state is fixed */
--
2.23.0
next prev parent reply other threads:[~2021-10-04 15:00 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-04 14:56 [PATCH 0/5] powerpc: various interrupt handling fixes Nicholas Piggin
2021-10-04 14:56 ` [PATCH 1/5] powerpc/64s: fix program check interrupt emergency stack path Nicholas Piggin
2021-10-04 14:56 ` [PATCH 2/5] powerpc/traps: do not enable irqs in _exception Nicholas Piggin
2021-10-04 14:56 ` [PATCH 3/5] powerpc/64: warn if local irqs are enabled in NMI or hardirq context Nicholas Piggin
2021-10-04 14:56 ` Nicholas Piggin [this message]
2021-10-04 14:56 ` [PATCH 5/5] powerpc/64s: Fix unrecoverable MCE calling async handler from NMI Nicholas Piggin
2021-10-04 15:28 ` Cédric Le Goater
2021-10-08 13:23 ` [PATCH 0/5] powerpc: various interrupt handling fixes Michael Ellerman
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