> >> Subject: Re: [PATCH v2 7/8] x86, perf: Only allow rdpmc if a perf_event is > >> mapped > >> > > CPU D CPU A > > switch_mm > > load_mm_cr4 > > x86_pmu_event_unmapped > > > > I wonder if the X86_CR4_PCE set on CPU D is > > cleared by CPU A by broadcasting IPI. > > > > It should be okay. The IPI does: > > + if (current->mm) > + load_mm_cr4(current->mm); > > which refers to the current task running on the targetted CPU, not to > the IPI sender's task. So, if it happens after a context switch, it > will harmlessly reload the new task's cr4. > Right, but prev != next is checked in switch_mm. Hillf
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