Messages in this thread | | | Date | Tue, 27 Feb 2024 14:05:05 -0800 | Subject | Re: [PATCH v3 1/2] x86/resctrl: Pass domain to target CPU | From | Reinette Chatre <> |
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Hi Tony,
On 2/22/2024 10:50 AM, 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. > > Adding the target domain to the msr_param structure, and calling > for each domain separately using smp_call_function_single() means > that rdt_ctrl_update() doesn't need to search for the domain. Thus > get_domain_from_cpu() can safely assert that the cpus_lock is held since > the remaining callers do not use IPI.
Please stick to the imperative tone. Something like (please feel free to improve):
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.
..
> @@ -463,6 +457,8 @@ static int domain_setup_ctrlval(struct rdt_resource *r, struct rdt_domain *d) > hw_dom->ctrl_val = dc; > setup_default_ctrlval(r, dc); > > + m.res = r;
This belongs in the next patch.
> + m.dom = d; > m.low = 0; > m.high = hw_res->num_closid; > hw_res->msr_update(d, &m, r);
The rest looks good to me and I think it is a good improvement. Thank you very much.
Reinette
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