Re: [PATCH v3 17/29] arm_mpam: Extend reset logic to allow devices to be reset any time

[Ben Horgan <ben.horgan@arm.com>]

Hi James,

On 10/17/25 19:56, James Morse wrote:
> cpuhp callbacks aren't the only time the MSC configuration may need to
> be reset. Resctrl has an API call to reset a class.
> If an MPAM error interrupt arrives it indicates the driver has
> misprogrammed an MSC. The safest thing to do is reset all the MSCs
> and disable MPAM.
> 
> Add a helper to reset RIS via their class. Call this from mpam_disable(),
> which can be scheduled from the error interrupt handler.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
> Reviewed-by: Ben Horgan <ben.horgan@arm.com>
> Tested-by: Fenghua Yu <fenghuay@nvidia.com>
> ---
> Changes since v2:
>  * Reduced the scop of arguments in mpam_reset_component_locked().
> 
> Changes since v1:
>  * more complete use of _srcu helpers.
>  * Use guard macro for srcu.
>  * Dropped a might_sleep() - something else will bark.
> ---
>  drivers/resctrl/mpam_devices.c | 58 ++++++++++++++++++++++++++++++++--
>  1 file changed, 55 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> index ec089593acad..545482e112b7 100644
> --- a/drivers/resctrl/mpam_devices.c
> +++ b/drivers/resctrl/mpam_devices.c
> @@ -802,15 +802,13 @@ static void mpam_reset_ris_partid(struct mpam_msc_ris *ris, u16 partid)
>  
>  /*
>   * Called via smp_call_on_cpu() to prevent migration, while still being
> - * pre-emptible.
> + * pre-emptible. Caller must hold mpam_srcu.
>   */
>  static int mpam_reset_ris(void *arg)
>  {
>  	u16 partid, partid_max;
>  	struct mpam_msc_ris *ris = arg;
>  
> -	WARN_ON_ONCE(!srcu_read_lock_held((&mpam_srcu)));
> -
>  	if (ris->in_reset_state)
>  		return 0;
>  
> @@ -1328,8 +1326,56 @@ static void mpam_enable_once(void)
>  	       mpam_partid_max + 1, mpam_pmg_max + 1);
>  }
>  
> +static void mpam_reset_component_locked(struct mpam_component *comp)
> +{
> +

Nit: Extra blank line.

> +	struct mpam_vmsc *vmsc;
> +
> +	lockdep_assert_cpus_held();
> +
> +	guard(srcu)(&mpam_srcu);
> +	list_for_each_entry_srcu(vmsc, &comp->vmsc, comp_list,
> +				 srcu_read_lock_held(&mpam_srcu)) {
> +		struct mpam_msc *msc = vmsc->msc;
> +		struct mpam_msc_ris *ris;
> +
> +		list_for_each_entry_srcu(ris, &vmsc->ris, vmsc_list,
> +					 srcu_read_lock_held(&mpam_srcu)) {
> +			if (!ris->in_reset_state)
> +				mpam_touch_msc(msc, mpam_reset_ris, ris);
> +			ris->in_reset_state = true;
> +		}
> +	}
> +}
> +

-- 
Thanks,

Ben