Re: [PATCH v5 1/2] x86/resctrl: Pass domain to target CPU

[Moger, Babu]

On 3/8/24 15:38, Tony Luck wrote:
> reset_all_ctrls() and resctrl_arch_update_domains() use on_each_cpu_mask()
> to call rdt_ctrl_update() on potentially one CPU from each domain.
> 
> But this means rdt_ctrl_update() needs to figure out which domain to
> apply changes to. Doing so requires a search of all domains in a resource,
> which can only be done safely if cpus_lock is held. Both callers do hold
> this lock, but there isn't a way for a function called on another CPU
> via IPI to verify this.
> 
> Commit c0d848fcb09d ("x86/resctrl: Remove lockdep annotation that triggers
> false positive") removed the incorrect assertions.
> 
> Add the target domain to the msr_param structure and
> call rdt_ctrl_update() for each domain separately using
> smp_call_function_single(). This means that rdt_ctrl_update() doesn't
> need to search for the domain and get_domain_from_cpu() can safely assert
> that the cpus_lock is held since the remaining callers do not use IPI.
> 
> Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
> Tested-by: Maciej Wieczor-Retman <maciej.wieczor-retman@xxxxxxxxx>
> Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
> Reviewed-by: James Morse <james.morse@xxxxxxx>

Reviewed-by: Babu Moger <babu.moger@xxxxxxx>