Re: [PATCH v3 09/16] x86/msr: Use the alternatives mechanism for WRMSR

[Jürgen Groß]

On 18.02.26 22:37, Dave Hansen wrote:
> On 2/18/26 13:00, Sean Christopherson wrote:
> > On Wed, Feb 18, 2026, Juergen Gross wrote:
> > > When available use one of the non-serializing WRMSR variants (WRMSRNS
> > > with or without an immediate operand specifying the MSR register) in
> > > __wrmsrq().
> > Silently using a non-serializing version (or not) seems dangerous (not for KVM,
> > but for the kernel at-large), unless the rule is going to be that MSR writes need
> > to be treated as non-serializing by default.
>
> Yeah, there's no way we can do this in general. It'll work for 99% of
> the MSRs on 99% of the systems for a long time. Then the one new system
> with WRMSRNS is going to have one hell of a heisenbug that'll take years
> off some poor schmuck's life.

I _really_ thought this was discussed upfront by Xin before he sent out his
first version of the series.

Sorry for not making it more clear in the header message.


Juergen

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