[PATCH] arm64: cpufeature: Add support for the MPAM v0.1 architecture version

[Ben Horgan]

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 at 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