Re: [PATCH v5 2/7] x86/msr: add wrmsrq_on_cpus helper

[Kalra, Ashish]

Hello Dave,

On 5/28/2026 2:50 PM, Dave Hansen wrote:
> On 5/28/26 12:37, Kalra, Ashish wrote:
>> A simple loop would be perfectly fine and avoids the need for the wrmsrq_on_cpus() helper entirely:
>>
>>   for_each_cpu(cpu, &rmpopt_cpumask)
>>       wrmsrq_on_cpu(cpu, MSR_AMD64_RMPOPT_BASE, rmpopt_base);
> 
> I'm glad we're on the same page finally. I just hope we can get to this
> point more quickly next time. I started off with exactly this
> suggestion, but someone chimed in to the thread and said it was "slower":
> 
>> https://lore.kernel.org/lkml/6a50d050-f602-43fd-a44a-cecedd9823eb@xxxxxxx/
> 

Yes, actually i should have made it explicitly clear that we need to do it in
parallel especially for issuing the RMPOPT instruction itself, as that is
in a performance critical path (and for that we are using on_each_cpu_mask()).

Thanks,
Ashish