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

[Kalra, Ashish]

On 5/28/2026 7:26 PM, Borislav Petkov wrote:
> On Thu, May 28, 2026 at 02:55:44PM -0500, Kalra, Ashish wrote:
>> 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()).
> 
> So which is it? Do we need the wrmsrq_on_cpus() helper or not?
> 
> I'm confused.
> 

No, we don't need it, i will drop this helper function patch.

Thanks,
Ashish