Messages in this thread | | | Date | Sun, 21 Mar 2004 11:30:59 +0100 | From | Manfred Spraul <> | Subject | Re: fixmap TLB flushing clarification |
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> > >I'm curious about the last statement, is this to mean that a TLB entry will >be reserved at set_fixmap() time in which the translation will happen, and >that particular entry will be locked down for the duration of the mapping? > > No. fixmap mappings are global - identical for all processes and all cpus. Therefore it's not necessary to flush them during a task switch. But that's just an optimization, not a mandatory feature: On x86 it's possible to mark page table entries as global. Global entries are not flushed by the normal tlb flush command, this gives a slighly better performance. If your architecture doesn't support that, then you can just flush everything during a task switch. I think the support for global entries was added for the Pentium cpus - 80486 cpus flush the whole tlb cache during a task switch.
-- Manfred
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