RE: [PATCH V2 1/2] x86/msr: add msr_set/clear_bit_on_cpu/cpus access functions

2017-03-27 Thread Liang, Kan
> > On Mon, Mar 27, 2017 at 08:47:37AM -0700, kan.li...@intel.com wrote: > > From: Kan Liang > > > > Having msr_set/clear_bit on many cpus or given CPU can avoid extra > > unnecessory IPIs > > How does that happen? > My previous patch did a read-modify-write operation. Compared with the single

Re: [PATCH V2 1/2] x86/msr: add msr_set/clear_bit_on_cpu/cpus access functions

2017-03-27 Thread Borislav Petkov
On Mon, Mar 27, 2017 at 08:47:37AM -0700, kan.li...@intel.com wrote: > From: Kan Liang > > 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 avoidi

[PATCH V2 1/2] x86/msr: add msr_set/clear_bit_on_cpu/cpus access functions

2017-03-27 Thread kan . liang
From: Kan Liang Having msr_set/clear_bit on many cpus or given CPU can avoid extra unnecessory IPIs 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 --- arch/x86/i