Messages in this thread | | | Date | Thu, 16 Oct 2014 10:26:24 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC 2/5] x86: Store a per-cpu shadow copy of CR4 |
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On Tue, Oct 14, 2014 at 03:57:36PM -0700, Andy Lutomirski wrote: > Context switches and TLB flushes can change individual bits of CR4. > CR4 reads take several cycles, so store a shadow copy of CR4 in a > per-cpu variable. > > To avoid wasting a cache line, I added the CR4 shadow to > cpu_tlbstate, which is already touched during context switches.
I'm a little confused. We should be more specific I suppose, context switches don't always change mm, but CR4 state is per task.
From a quick look, only switch_mm() pokes at tlb, switch_to() does not.
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