From: Ben Horgan <ben.horgan@arm.com>
To: Zeng Heng <zengheng4@huawei.com>,
james.morse@arm.com, miko.lenczewski@arm.com, thuth@redhat.com,
mark.rutland@arm.com, yeoreum.yun@arm.com, robh@kernel.org,
james.clark@linaro.org, ahmed.genidi@arm.com, xry111@xry111.site,
oupton@kernel.org, lpieralisi@kernel.org,
catalin.marinas@arm.com, mrigendra.chaubey@gmail.com,
suzuki.poulose@arm.com, maz@kernel.org, ardb@kernel.org,
broonie@kernel.org, will@kernel.org, kevin.brodsky@arm.com,
leo.yan@arm.com, anshuman.khandual@arm.com,
yang@os.amperecomputing.com, frederic@kernel.org
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, bobo.shaobowang@huawei.com
Subject: Re: [PATCH] arm64: cpufeature: Add support for the MPAM v0.1 architecture version
Date: Tue, 27 Jan 2026 14:30:37 +0000 [thread overview]
Message-ID: <37f87d5d-bd70-4b13-93e0-8024108be948@arm.com> (raw)
In-Reply-To: <20260104133434.1887677-1-zengheng4@huawei.com>
Hi Zeng,
On 1/4/26 13:34, Zeng Heng wrote:
> According to the MPAM spec [1], the supported architecture versions are
> v1.0, v1.1 and v0.1. MPAM versions v0.1 and v1.1 are functionally
> identical, but v0.1 additionally supports the FORCE_NS feature.
>
> ID_AA64PR | ID_AA64PR | MPAM Extension | Notes
> F0_EL1. | F1_EL1. | Architecture |
> MPAM | MPAM_frac | version |
> ---------------------------------------------------------------------------
> 0b0000 | 0b0001 | v0.1 | MPAM v0.1 is implemented.
> | | | MPAM v0.1 is the same as MPAM v1.1
> | | | with FORCE_NS which is
> | | | incompatible with MPAM v1.0.
> ---------------------------------------------------------------------------
> 0b0001 | 0b0000 | v1.0 | MPAM v1.0 is implemented.
> ---------------------------------------------------------------------------
> 0b0001 | 0b0001 | v1.1 | MPAM v1.1 is implemented.
> | | | MPAM v1.1 includes all features of
> | | | MPAM v1.0.
> | | | It must not include FORCE_NS.
>
> FORCE_NS is a feature that operates in EL3 mode. Consequently, the current
> Linux MPAM driver is also compatible with MPAM v0.1. To support v0.1, the
> existing driver which only checks ID_AA64PFR0_EL1.MPAM for the major
> version needs to examine ID_AA64PFR1_EL1.MPAM_frac for the minor version
> as well.
>
> [1] https://developer.arm.com/documentation/ddi0598/db/?lang=en
>
> Signed-off-by: Zeng Heng <zengheng4@huawei.com>
So far we've avoided added MPAM 0.1 support as we don't know of any
machines using it. What's your motivation here? Do you have a machine
with MPAM 0.1 that runs mainline linux?
Thanks,
Ben
next prev parent reply other threads:[~2026-01-27 14:30 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-04 13:34 Zeng Heng
2026-01-27 14:30 ` Ben Horgan [this message]
2026-01-28 8:54 ` Zeng Heng
2026-01-28 14:37 ` Ben Horgan
2026-01-28 15:55 ` Ben Horgan
2026-01-28 16:29 ` Ben Horgan
2026-02-02 13:13 ` Zeng Heng
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