Re: [PATCH v2 06/45] KVM: arm64: Make MPAMSM_EL1 accesses UNDEF

Jonathan Cameron
2026-01-05T16:47:44Z

On Fri, 19 Dec 2025 18:11:08 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> The MPAMSM_EL1 controls the MPAM labeling for an SMCU, Streaming Mode
> Compute Unit. As there is on MPAM support in kvm, make sure MPAMSM_EL1
> accesses trigger an UNDEF.
>
> The range of valid configurations for the PARTID and PMG in MPAMSM_EL1 is
> not currently specified in Arm Architectural Reference Manual but the
> architect has confirmed that it is intended to be the same as that for the
> cpu configuration in the MPAMy_ELx registers.

Good to know but I'm not seeing why it matters in this patch. Perhaps
a little more on that?

>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> ---
> arch/arm64/kvm/sys_regs.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index c8fd7c6a12a1..72654ab984ee 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -3373,6 +3373,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>
> { SYS_DESC(SYS_MPAM1_EL1), undef_access },
> { SYS_DESC(SYS_MPAM0_EL1), undef_access },
> + { SYS_DESC(SYS_MPAMSM_EL1), undef_access },
> +
> { SYS_DESC(SYS_VBAR_EL1), access_rw, reset_val, VBAR_EL1, 0 },
> { SYS_DESC(SYS_DISR_EL1), NULL, reset_val, DISR_EL1, 0 },
>