From: Marc Zyngier <maz@kernel.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org, broonie@kernel.org,
catalin.marinas@arm.com, will@kernel.org
Subject: Re: [PATCH v2 0/5] arm64: pseudo-nmi: elide code when CONFIG_ARM64_PSEUDO_NMI=n
Date: Thu, 26 Jan 2023 08:51:21 +0000 [thread overview]
Message-ID: <875yctel12.wl-maz@kernel.org> (raw)
In-Reply-To: <20230125163826.496739-1-mark.rutland@arm.com>
On Wed, 25 Jan 2023 16:38:21 +0000,
Mark Rutland <mark.rutland@arm.com> wrote:
>
> This series addresses a couple of sub-optimal code generation issues with
> arm64's pseudo-nmi support code:
>
> * Even when CONFIG_ARM64_PSEUDO_NMI=n, we generate alternative code
> sequences and alt_instr entries which will never be used. This series
> reworks the irqflags code to use alternative branches (with an
> IS_ENABLED() check), which allows the alternatives to be elided when
> CONFIG_ARM64_PSEUDO_NMI=n.
>
> * When PMHE is eanbled in HW, we must synchronize PMR updates using a
> DSB SY. We take pains to avoid this using a static key to skip the
> barrier when PMHE is not in use, but this results in unnecessarily
> branchy code. This series replaces the static key with an alternative,
> allowing the DSB SY to be relaxed to a NOP.
>
> These changes make a defconfig kernel a little smaller, and does not
> adversely affect the size of a CONFIG_ARM64_PSEUDO_NMI=y kernel. The
> structural changes will also make it easier for a subsequent series to
> rework the irqflag and daifflag management, addressing some
> long-standing edge cases and preparing for ARMv8.8-A's FEAT_NMI.
>
> I've tested this series under a QEM KVM VM on a ThunderX2 host, and a
> QEMU TCG VM on an x86_64 host. I've tested with and without pseudo-NMI
> support enabled, and with pseudo-NMI debug and lockdep enabled, using
> perf record in system-wide mode.
With the couple of nits I mentioned on individual patches addressed:
Reviewed-by: Marc Zyngier <maz@kernel.org>
M.
--
Without deviation from the norm, progress is not possible.
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prev parent reply other threads:[~2023-01-26 8:54 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-25 16:38 [PATCH v2 0/5] arm64: pseudo-nmi: elide code when CONFIG_ARM64_PSEUDO_NMI=n Mark Rutland
2023-01-25 16:38 ` [PATCH v2 1/5] arm64: rename ARM64_HAS_SYSREG_GIC_CPUIF to ARM64_HAS_GIC_CPUIF_SYSREGS Mark Rutland
2023-01-25 16:38 ` [PATCH v2 2/5] arm64: rename ARM64_HAS_IRQ_PRIO_MASKING to ARM64_HAS_GIC_PRIO_MASKING Mark Rutland
2023-01-25 16:38 ` [PATCH v2 3/5] arm64: make ARM64_HAS_GIC_PRIO_MASKING depend on ARM64_HAS_GIC_PRIO_MASKING Mark Rutland
2023-01-25 18:05 ` Alexandru Elisei
2023-01-25 18:27 ` Mark Rutland
2023-01-25 16:38 ` [PATCH v2 4/5] arm64: add ARM64_HAS_GIC_PRIO_RELAXED_SYNC cpucap Mark Rutland
2023-01-26 8:31 ` Marc Zyngier
2023-01-26 10:24 ` Mark Rutland
2023-01-25 16:38 ` [PATCH v2 5/5] arm64: irqflags: use alternative branches for pseudo-NMI logic Mark Rutland
2023-01-26 8:49 ` Marc Zyngier
2023-01-26 10:31 ` Mark Rutland
2023-01-26 8:51 ` Marc Zyngier [this message]
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