Messages in this thread | | | Date | Mon, 15 Dec 2008 17:28:19 -0800 | From | Jeremy Fitzhardinge <> | Subject | Re: [PATCH RFC] vm_unmap_aliases: allow callers to inhibit TLB flush |
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Nick Piggin wrote: > On Friday 12 December 2008 12:59, Jeremy Fitzhardinge wrote: > >> Nick Piggin wrote: >> >>> Hi, >>> >>> On Friday 12 December 2008 06:05, Jeremy Fitzhardinge wrote: >>> >>>> Hi Nick, >>>> >>>> In Xen when we're killing the lazy vmalloc aliases, we're only concerned >>>> about the pagetable references to the mapped pages, not the TLB entries. >>>> >>> Hm? Why is that? Why wouldn't it matter if some page table page gets >>> written to via a stale TLB? >>> >> No. Well, yes, it would, but Xen itself will do whatever tlb flushes >> are necessary to keep it safe (it must, since it doesn't trust guest >> kernels). It's fairly clever about working out which cpus need flushing >> and if other flushes have already done the job. >> > > OK. Yeah, then the problem is simply that the guest may reuse that virtual > memory for another vmap. >
Hm. What you would you think of a "deferred tlb flush" flag (or something) to cause the next vmap to do the tlb flushes, in the case the vunmap happens in a context where the flushes can't be done?
J
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