Re: [PATCH v2 00/29] arm_mpam: Add basic mpam driver

Fenghua Yu
2025-09-25T07:18:58Z

On 9/10/25 13:42, James Morse wrote:
> Hello,
>
> The major changes since v1 are:
> * DT got ripped out - see below.
> * The mon_sel locking was simplified - but that will come back.
>
> Otherwise the myriad of changes are noted on each patch.
>
> ~
>
> This is just enough MPAM driver for ACPI. DT got ripped out. If you need DT
> support - please share your DTS so the DT folk know the binding is what is
> needed.
> This doesn't contain any of the resctrl code, meaning you can't actually drive it
> from user-space yet. Becuase of that, its hidden behind CONFIG_EXPERT.
> This will change once the user interface is connected up.
>
> This is the initial group of patches that allows the resctrl code to be built
> on top. Including that will increase the number of trees that may need to
> coordinate, so breaking it up make sense.
>
> The locking got simplified, but is still strange - this is because of the 'mpam-fb'
> firmware interface specification that is still alpha. That thing needs to wait for
> an interrupt after every system register write, which significantly impacts the
> driver. Some features just won't work, e.g. reading the monitor registers via
> perf.
>
> I've not found a platform that can test all the behaviours around the monitors,
> so this is where I'd expect the most bugs.
>
> The MPAM spec that describes all the system and MMIO registers can be found here:
> https://developer.arm.com/documentation/ddi0598/db/?lang=en
> (Ignored the 'RETIRED' warning - that is just arm moving the documentation around.
> This document has the best overview)
>
> The expectation is this will go via the arm64 tree.
>
>
> This series is based on v6.17-rc4, and can be retrieved from:
> https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git mpam/driver/v2
>
> The rest of the driver can be found here:
> https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git mpam/snapshot/v6.17-rc4

Tested-by: Fenghua Yu <fenghuay@nvidia.com>

[SNIP]

Thanks.

-Fenghua