Subject: Re: [PATCH v3 4/4] arm_mpam: Update architecture version check for MPAM MSC

From: Ben Horgan <[email-masked]>
Date: Fri, 8 May 2026 17:35:21 +0100

Hi James,

On 5/8/26 17:23, James Morse wrote:
> From: Zeng Heng <[email-masked]>
> 
> In addition to updating the CPU MPAM version check, the MPAM MSC version
> check also need to be updated. mpam_msc_check_aidr() is added to check
> the MSC AIDR register, ensuring that both the major and minor version
> numbers fall within the supported range of the MPAM architecture version.
> 
> Signed-off-by: Zeng Heng <[email-masked]>
> [ morse: changed mpam_msc_check_aidr() to accept versions like v1.2 ]
> Signed-off-by: James Morse <[email-masked]>
> ---
>  drivers/resctrl/mpam_devices.c | 23 ++++++++++++++++++++---
>  1 file changed, 20 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> index 916d8fd45ed5..1771e9712ca2 100644
> --- a/drivers/resctrl/mpam_devices.c
> +++ b/drivers/resctrl/mpam_devices.c
> @@ -224,6 +224,24 @@ static inline void _mpam_write_monsel_reg(struct mpam_msc *msc, u16 reg, u32 val
>  
>  #define mpam_write_monsel_reg(msc, reg, val)   _mpam_write_monsel_reg(msc, MSMON_##reg, val)
>  
> +static bool mpam_msc_check_aidr(struct mpam_msc *msc)
> +{
> +	u32 aidr = __mpam_read_reg(msc, MPAMF_AIDR);
> +	u32 major = FIELD_GET(MPAMF_AIDR_ARCH_MAJOR_REV, aidr);
> +	u32 minor = FIELD_GET(MPAMF_AIDR_ARCH_MINOR_REV, aidr);
> +
> +	/*
> +	 * v0.0 and >v2.x aren't supported, but anything else should be backward
> +	 * compatible to v0.1 or v1.0.
> +	 */
> +	if (!major && !minor)
> +		return false;
> +	if (major > 1)
> +		return false;
> +
> +	return true;
> +}
> +
>  static u64 mpam_msc_read_idr(struct mpam_msc *msc)
>  {
>  	u64 idr_high = 0, idr_low;
> @@ -951,9 +969,8 @@ static int mpam_msc_hw_probe(struct mpam_msc *msc)
>  
>  	lockdep_assert_held(&msc->probe_lock);
>  
> -	idr = __mpam_read_reg(msc, MPAMF_AIDR);
> -	if ((idr & MPAMF_AIDR_ARCH_MAJOR_REV) != MPAM_ARCHITECTURE_V1) {

nit: MPAM_ARCHITECTURE_V1 is now unused.

Reviewed-by: Ben Horgan <[email-masked]>

Thanks,

Ben

> -		dev_err_once(dev, "MSC does not match MPAM architecture v1.x\n");
> +	if (!mpam_msc_check_aidr(msc)) {
> +		dev_err_once(dev, "MSC does not match architecture v1.x\n");
>  		return -EIO;
>  	}
>