linux-kernel - [PATCH 0/2] arm64: fix lockdep in NMI context

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Message-Id: <20220511131733.4074499-1-mark.rutland@arm.com>
Date:   Wed, 11 May 2022 14:17:31 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     catalin.marinas@....com, linux-kernel@...r.kernel.org,
        mark.rutland@....com, mingo@...nel.org, peterz@...radead.org,
        tglx@...utronix.de, will@...nel.org
Subject: [PATCH 0/2] arm64: fix lockdep in NMI context

For lockdep to function correctly in NMI context, architectures need to
correctly save/restore lockdep state at NMI entry/exit time, correctly
manage lockdep state within the NMI context, and need to select
TRACE_IRQFLAGS_NMI_SUPPORT.

Currently arm64 falls short of this merely by failing to select
TRACE_IRQFLAGS_NMI_SUPPORT, and this can result in spurious lockdep
splats with GICv3 Pseudo-NMIs are in use. Patch 2 has an example.

Patch 1 makes TRACE_IRQFLAGS_NMI_SUPPORT a generically selectable
kconfig symbol (as it is currently defined under arch/x86). Patch 2
selects this on arm64 (providing the behaviour we'd intended when
reworking our entry code).

For anyone testing, beware that there are some other latent issues with
GICv3 Pseudo-NMIs. I'm currently working to fix those whcih I am aware
of, but as this is orthogonal I'd like to get it out the way on its own.

Thanks,
Mark.

Mark Rutland (2):
  arch: make TRACE_IRQFLAGS_NMI_SUPPORT generic
  arm64: select TRACE_IRQFLAGS_NMI_SUPPORT

 arch/Kconfig           | 3 +++
 arch/arm64/Kconfig     | 1 +
 arch/x86/Kconfig       | 1 +
 arch/x86/Kconfig.debug | 3 ---
 4 files changed, 5 insertions(+), 3 deletions(-)

-- 
2.30.2