Messages in this thread | | | Date | Tue, 28 Oct 2014 08:18:39 -0700 | Subject | Re: [RFC PATCH 2/2] zap_pte_range: fix partial TLB flushing in response to a dirty pte | From | Linus Torvalds <> |
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On Tue, Oct 28, 2014 at 4:44 AM, Will Deacon <will.deacon@arm.com> wrote: > @@ -1194,11 +1194,10 @@ again: > * then update the range to be the remaining > * TLB range. > */ > - old_end = tlb->end; > - tlb->end = addr; > + tlb->end = old_end = min(tlb->end, addr); > tlb_flush_mmu_tlbonly(tlb); > - tlb->start = addr; > - tlb->end = old_end; > + tlb->start = old_end; > + tlb->end = end;
I don't think this is right. Setting "tlb->end = end" looks very wrong indeed, because "end" here inside zap_pte_range() is *not* the final end of the zap range, it is just the end of the current set of pte's.
There's a reason the old code *saved* the old end value. You've now ripped that out, and use the "old_end" for something else entirely.
Your arm64 version of tlb_add_flush() then hides the bug you just introduced by updating the end range for each page you encounter. But quite frankly, I think your problems are all fundamental to that very issue. You're playing games with start/end during the TLB flush itself, which is not how those things were designed to work.
So now you break everything that *doesn't* do your arm games.
Linus
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