Messages in this thread | | | From | Andi Kleen <> | Subject | Re: [patch] x86, mm: avoid stale tlb entries by clearing prev mm_cpumask after switching mm | Date | Wed, 02 Feb 2011 17:23:53 -0800 |
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Suresh Siddha <suresh.b.siddha@intel.com> writes:
> For the prev mm that is handing over the cpu to another mm, clear the cpu > from the mm_cpumask(prev) after the cr3 is changed. > > Otherwise, clearing the mm_cpumask early will avoid the flush tlb IPI's while > the cr3 and TLB's are still pointing to the prev mm. And this window can lead > to the stale (global) TLB entries. > > Marking it for -stable, though we haven't seen any reported failure that > can be attributed to this.
Would it be safer to add a memory barrier between the load_cr3 and the cpumask_clear_cpu()? As far as I can see cpumask_clear_cpu doesn't imply a general one and load_cr3 doesn't either. There's this __force_order hack in system.h, but I don't think it will enforce order here.
-Andi
-- ak@linux.intel.com -- Speaking for myself only
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