Re: [PATCH 2/6] x86/sev: add support for enabling RMPOPT

[Dave Hansen]

On 2/18/26 09:07, Kalra, Ashish wrote:
> On 2/18/2026 11:01 AM, Dave Hansen wrote:
>> On 2/18/26 08:55, Kalra, Ashish wrote:
>>> Because, setting RMPOPT_BASE MSR (which is a per-core MSR) and
>>> RMPOPT instruction need to be issued on only one thread per core. If
>>> the primary thread is offlined and secondary thread is not
>>> considered, we will miss/skip setting either the RMPOPT_BASE MSR or
>>> not issuing the RMPOPT instruction for that physical CPU, which
>>> means no RMP optimizations enabled for that physical CPU.
>> What is the harm of issuing it twice per core?
> Why to issue it if we can avoid it.
> 
> It is not that complex to setup a cpumask containing the online primary
> or secondary thread and then issue the RMPOPT instruction only once per
> thread.

It's a non-zero amount of error-prone kernel code. It *is* complex. It
has to be reviewed and maintained.

Please remove this unnecessary optimization from the series. If you
would like to add it back, please do it in a patch at the end so it can
be evaluated on its own. Include performance numbers so the code
complexity can be balanced against the performance gain.