[PATCH v4 3/7] arm64: cpufeature: discover CPU support for MPAM

[Gavin Shan]

On 10/4/24 9:07 PM, Joey Gouly wrote:
> From: James Morse <james.morse at arm.com>
> 
> ARMv8.4 adds support for 'Memory Partitioning And Monitoring' (MPAM)
> which describes an interface to cache and bandwidth controls wherever
> they appear in the system.
> 
> Add support to detect MPAM. Like SVE, MPAM has an extra id register that
> describes some more properties, including the virtualisation support,
> which is optional. Detect this separately so we can detect
> mismatched/insane systems, but still use MPAM on the host even if the
> virtualisation support is missing.
> 
> MPAM needs enabling at the highest implemented exception level, otherwise
> the register accesses trap. The 'enabled' flag is accessible to lower
> exception levels, but its in a register that traps when MPAM isn't enabled.
> The cpufeature 'matches' hook is extended to test this on one of the
> CPUs, so that firmware can emulate MPAM as disabled if it is reserved
> for use by secure world.
> 
> Secondary CPUs that appear late could trip cpufeature's 'lower safe'
> behaviour after the MPAM properties have been advertised to user-space.
> Add a verify call to ensure late secondaries match the existing CPUs.
> 
> (If you have a boot failure that bisects here its likely your CPUs
> advertise MPAM in the id registers, but firmware failed to either enable
> or MPAM, or emulate the trap as if it were disabled)
> 
> Signed-off-by: James Morse <james.morse at arm.com>
> Signed-off-by: Joey Gouly <joey.gouly at arm.com>
> ---
> Changes since v3:
>   * A proper conversion to sysreg
> ---
>   .../arch/arm64/cpu-feature-registers.rst      |  2 +
>   arch/arm64/Kconfig                            | 20 ++++
>   arch/arm64/include/asm/cpu.h                  |  1 +
>   arch/arm64/include/asm/cpucaps.h              |  2 +
>   arch/arm64/include/asm/cpufeature.h           | 12 +++
>   arch/arm64/include/asm/mpam.h                 | 32 ++++++
>   arch/arm64/kernel/Makefile                    |  2 +
>   arch/arm64/kernel/cpufeature.c                | 97 +++++++++++++++++++
>   arch/arm64/kernel/cpuinfo.c                   |  4 +
>   arch/arm64/kernel/mpam.c                      |  8 ++
>   arch/arm64/tools/cpucaps                      |  1 +
>   11 files changed, 181 insertions(+)
>   create mode 100644 arch/arm64/include/asm/mpam.h
>   create mode 100644 arch/arm64/kernel/mpam.c
> 

[...]

> diff --git a/arch/arm64/kernel/mpam.c b/arch/arm64/kernel/mpam.c
> new file mode 100644
> index 000000000000..a29dc58c2da5
> --- /dev/null
> +++ b/arch/arm64/kernel/mpam.c
> @@ -0,0 +1,8 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (C) 2021 Arm Ltd. */
> +
> +#include <asm/mpam.h>
> +
> +#include <linux/jump_label.h>
> +
> +DEFINE_STATIC_KEY_FALSE(arm64_mpam_has_hcr);

linux/jump_label.h has been included to asm/mpam.h. So we needn't include
it again.

Thanks,
Gavin