Re: [RFC PATCH v1 01/15] x86/msr: Replace __wrmsr() with native_wrmsrl()

[Xin Li <xin@xxxxxxxxx>]

On 3/31/2025 10:13 PM, H. Peter Anvin wrote:
> On March 31, 2025 2:45:43 PM PDT, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> 
> wrote:
> > On 31/03/2025 9:22 am, Xin Li (Intel) wrote:
> > > __wrmsr() is the lowest level primitive MSR write API, and its direct
> > > use is NOT preferred.  Use its wrapper function native_wrmsrl() instead.
> > >
> > > No functional change intended.
> > >
> > > Signed-off-by: Xin Li (Intel) <xin@xxxxxxxxx>
> > The critical piece of information you're missing from the commit message
> > is that the MSR_IMM instructions take a single u64.
> >
> > Therefore to use them, you've got to arrange for all callers to provide
> > a single u64, rather than a split u32 pair.
> >
> > ~Andrew
> That being said, there is nothing wrong with having a two-word convenience 
> wrapper.
Yes, I ended up keeping the two-word convenience wrapper in this patch
set, and the wrapper calls a lower level API that takes a u64 argument.

And yes, as Ingo said, some of the conversion is NOT an improvement.