linux-kernel - Re: [PATCH v3 0/8] Rework the DAIF mask, unmask and track API

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Date: Fri, 3 May 2024 18:10:14 +0100
From: Mark Rutland <mark.rutland@....com>
To: Liao Chang <liaochang1@...wei.com>
Cc: catalin.marinas@....com, will@...nel.org, maz@...nel.org,
	oliver.upton@...ux.dev, james.morse@....com, suzuki.poulose@....com,
	yuzenghui@...wei.com, tglx@...utronix.de, ardb@...nel.org,
	broonie@...nel.org, anshuman.khandual@....com,
	miguel.luis@...cle.com, joey.gouly@....com, ryan.roberts@....com,
	jeremy.linton@....com, ericchancf@...gle.com,
	kristina.martsenko@....com, robh@...nel.org,
	scott@...amperecomputing.com, songshuaishuai@...ylab.org,
	shijie@...amperecomputing.com, akpm@...ux-foundation.org,
	bhe@...hat.com, horms@...nel.org, mhiramat@...nel.org,
	rmk+kernel@...linux.org.uk, shahuang@...hat.com,
	takakura@...inux.co.jp, dianders@...omium.org, swboyd@...omium.org,
	sumit.garg@...aro.org, frederic@...nel.org, reijiw@...gle.com,
	akihiko.odaki@...nix.com, ruanjinjie@...wei.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kvmarm@...ts.linux.dev
Subject: Re: [PATCH v3 0/8] Rework the DAIF mask, unmask and track API

Hi,

On Mon, Apr 15, 2024 at 06:47:50AM +0000, Liao Chang wrote:
> This patch series reworks the DAIF mask, unmask, and track API for the
> upcoming FEAT_NMI extension added in Armv8.8.
> 
> As platform and virtualization[1] supports for FEAT_NMI is emerging, and
> Mark Brown's FEAT_NMI patch series[2] highlighted the need for clean up
> the existing hacking style approach about DAIF management code before
> adding NMI functionality, furthermore, we discover some subtle bugs
> during 'perf' and 'ipi_backtrace' transition from PSEUDO_NMI to
> FEAT_NMI, in summary, all of these emphasize the importance of rework.
> 
> This series of reworking patches follows the suggestion from Mark
> Rutland mentioned in Mark Brown's patchset. In summary, he think the
> better way for DAIF manangement look likes as following:
> 
> (a) Adding entry-specific helpers to manipulate abstract exception masks
>     covering DAIF + PMR + ALLINT. Those need unmask-at-entry and
>     mask-at-exit behaviour, and today only need to manage DAIF + PMR.
> 
>     It should be possible to do this ahead of ALLINT / NMI support.
> 
> (b) Adding new "logical exception mask" helpers that treat DAIF + PMR +
>     ALLINT as separate elements. 

I've started looking at this in the series. There are some subtleties here, and
I don't think the helpers in this series are quite right as-is. I will try to
get back to you next week with a description of those; it'll take a short while
to write that up correctly and clearly and I don't trust myself to rush that
last thing on a Friday.

Thanks,
Mark.

> 
> This patches cherry-pick a part of Mark Brown' FEAT_NMI series, in order
> to pass compilation and basic testing, includes perf and ipi_backtrace.
> 
> [1] https://lore.kernel.org/all/20240407081733.3231820-1-ruanjinjie@huawei.com/
> [2] https://lore.kernel.org/linux-arm-kernel/Y4sH5qX5bK9xfEBp@lpieralisi/
> 
> v3->v2:
> 1. Squash two commits that address two minor issues into Mark Brown's
>    origin patch for detecting FEAT_NMI.
> 2. Add one patch resolves the kprobe reenter panic while testing
>    FEAT_NMI on QEMU.
> 
> v2->v1:
> Add SoB tags following the origin author's SoBs.
> 
> Liao Chang (5):
>   arm64: daifflags: Add logical exception masks covering DAIF + PMR +
>     ALLINT
>   arm64: Unify exception masking at entry and exit of exception
>   arm64: Deprecate old local_daif_{mask,save,restore}
>   irqchip/gic-v3: Improve the maintainability of NMI masking in GIC
>     driver
>   arm64: kprobe: Keep NMI maskabled while kprobe is stepping xol
> 
> Mark Brown (3):
>   arm64/sysreg: Add definitions for immediate versions of MSR ALLINT
>   arm64/cpufeature: Detect PE support for FEAT_NMI
>   arm64/nmi: Add Kconfig for NMI
> 
>  arch/arm64/Kconfig                   |  17 ++
>  arch/arm64/include/asm/cpufeature.h  |   6 +
>  arch/arm64/include/asm/daifflags.h   | 298 ++++++++++++++++++++++-----
>  arch/arm64/include/asm/nmi.h         |  27 +++
>  arch/arm64/include/asm/sysreg.h      |   2 +
>  arch/arm64/include/uapi/asm/ptrace.h |   1 +
>  arch/arm64/kernel/acpi.c             |  10 +-
>  arch/arm64/kernel/cpufeature.c       |  58 +++++-
>  arch/arm64/kernel/debug-monitors.c   |   7 +-
>  arch/arm64/kernel/entry-common.c     |  96 +++++----
>  arch/arm64/kernel/entry.S            |   2 -
>  arch/arm64/kernel/hibernate.c        |   6 +-
>  arch/arm64/kernel/irq.c              |   2 +-
>  arch/arm64/kernel/machine_kexec.c    |   2 +-
>  arch/arm64/kernel/probes/kprobes.c   |   4 +-
>  arch/arm64/kernel/setup.c            |   2 +-
>  arch/arm64/kernel/smp.c              |   6 +-
>  arch/arm64/kernel/suspend.c          |   6 +-
>  arch/arm64/kvm/hyp/vgic-v3-sr.c      |   6 +-
>  arch/arm64/kvm/hyp/vhe/switch.c      |   4 +-
>  arch/arm64/mm/mmu.c                  |   6 +-
>  arch/arm64/tools/cpucaps             |   2 +
>  drivers/irqchip/irq-gic-v3.c         |   6 +-
>  23 files changed, 442 insertions(+), 134 deletions(-)
>  create mode 100644 arch/arm64/include/asm/nmi.h
> 
> -- 
> 2.34.1
> 
>