Messages in this thread Patch in this message | | | Date | Mon, 27 Mar 2017 18:57:10 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH V2 1/2] x86/msr: add msr_set/clear_bit_on_cpu/cpus access functions |
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On Mon, Mar 27, 2017 at 08:47:37AM -0700, kan.liang@intel.com wrote: > From: Kan Liang <Kan.liang@intel.com> > > Having msr_set/clear_bit on many cpus or given CPU can avoid extra > unnecessory IPIs
How does that happen?
You have smp_call_function_many() sending IPIs to each CPU in the mask. Doesn't look like avoiding anything to me.
Now if you want to have interfaces set/clear_bit_on_cpu(s), that's a different story.
And those actually double the amount of IPIs the moment you do a read-modify-write operation on the MSR, i.e., you want to read *and* write afterwards.
If you only want to do a single operation - set or clear - like you're doing in your other patch, then I guess that's fine as it wraps the smp_call_function* boilerplate code.
> and simplify MSR content manipulation, when it only > needs to flip a bit. > There is already msr_set/clear_bit, but missing the _on_cpu and _on_cpus > version. > > Signed-off-by: Kan Liang <Kan.liang@intel.com> > --- > arch/x86/include/asm/msr.h | 29 ++++++++++++++++++ > arch/x86/lib/msr-smp.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 105 insertions(+) > > diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h > index 898dba2..9bc999b 100644 > --- a/arch/x86/include/asm/msr.h > +++ b/arch/x86/include/asm/msr.h > @@ -20,6 +20,11 @@ struct msr { > }; > }; > > +struct msr_bit_info { > + u32 msr_no; > + u8 bit; > +};
No, not *another* struct msr*info. Please reuse msr_info.
-- Regards/Gruss, Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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