linux-kernel - Re: [PATCH v2 06/45] KVM: arm64: Make MPAMSM

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Message-ID: <20260105164738.0000792f@huawei.com>
Date: Mon, 5 Jan 2026 16:47:38 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Ben Horgan <ben.horgan@....com>
CC: <amitsinght@...vell.com>, <baisheng.gao@...soc.com>,
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Subject: Re: [PATCH v2 06/45] KVM: arm64: Make MPAMSM_EL1 accesses UNDEF

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

Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.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 },
>