Re: [PATCH v2 07/10] x86/msr: Switch rdmsr_safe_on_cpu() users to rdmsrq_safe_on_cpu()

[Jürgen Groß]

On 06.06.26 11:51, Ingo Molnar wrote:
> * Juergen Gross <jgross@xxxxxxxx> wrote:
>
> > In order to prepare retiring rdmsr_safe_on_cpu() switch
> > rdmsr_safe_on_cpu() users to rdmsrq_safe_on_cpu().
>
> > --- a/arch/x86/lib/msr-smp.c
> > +++ b/arch/x86/lib/msr-smp.c
> > @@ -190,11 +190,22 @@ EXPORT_SYMBOL(wrmsrq_safe_on_cpu);
> >   
> >   int rdmsrq_safe_on_cpu(unsigned int cpu, u32 msr_no, u64 *q)
> >   {
> > -	u32 low, high;
> > +	struct msr_info_completion rv;
> > +	call_single_data_t csd;
> >   	int err;
> >   
> > -	err = rdmsr_safe_on_cpu(cpu, msr_no, &low, &high);
> > -	*q = (u64)high << 32 | low;
> > +	INIT_CSD(&csd, __rdmsr_safe_on_cpu, &rv);
> > +
> > +	memset(&rv, 0, sizeof(rv));
> > +	init_completion(&rv.done);
> > +	rv.msr.msr_no = msr_no;
> > +
> > +	err = smp_call_function_single_async(cpu, &csd);
> > +	if (!err) {
> > +		wait_for_completion(&rv.done);
> > +		err = rv.msr.err;
> > +	}
> > +	*q = rv.msr.reg.q;
>
> While technically this is another API user conversion,
> I'd split this out into another preparatory patch,
> because this changes the API itself.

Okay, fine with me.

I'll send V3 after rc1 of 7.2 as Dave suggested.

One final question (not directly for this series, but for a future one):

I'd like to switch rdmsrq() from a macro to an inline function, as a macro
using one of its parameters as the destination for an assignment isn't
nice. Additionally I'd like to replace rdmsr*() use cases with rdmsrq*()
and wrmsr*() with wrmsrq*() (similar to the replacements done is this
series).

The rdmsrq() transformation into a function can easily be done via a
coccinelle script. What would be your choice regarding the sequence doing
this?

a) Start with rdmsrq() transformation into a function.
b) First do the rdmsr/wrmsr -> rdmsrq/wrmsrq replacements, then do the
   rdmsrq() transformation into a function (this will touch more code, as
   the initial rdmsr() use cases will be affected, too).
c) Leave rdmsrq() as a macro.


Juergen

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