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

Ben Horgan
2026-01-05T16:57:17Z

Hi Jonathan,

On 1/5/26 16:47, Jonathan Cameron wrote:
> 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?

Hmmm, yes. This paragraph should go with patch 11 where we start setting
MPAMSM_EL1 with the same value as MPAM0_EL1 and MPAM1_EL1.

>
>>
>> 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 },
>>
>

Thanks,

Ben