Re: [PATCH 4/7] x86,tlb: make lazy TLB mode lazier

[Vitaly Kuznetsov]

Andy Lutomirski <luto@xxxxxxxxxxxxxx> writes:

> [I added PeterZ and Vitaly -- can you see any way in which this would
> break something obscure?  I don't.]

Thanks for CCing me,

I don't see how this can break things either. At first glance, however,
I'm afraid we can add performance penalty to virtualized guests which
don't use native_flush_tlb_others() (Hyper-V, KVM): we will be reloading
CR3 without a need as we don't look at lazy mode in PV tlb flush
functions.

We can either check to switch_mm_irqs_off() that
native_flush_tlb_others() is in use or teach PV tlb flush functions to
look at lazy mode too.

(Sorry if I'm missing something important here or if this was already
discussed. I just became aware of this work)

[...]

-- 
  Vitaly