Messages in this thread | | | Subject | Re: [PATCH] mmu notifiers #v2 | From | Benjamin Herrenschmidt <> | Date | Tue, 15 Jan 2008 15:28:27 +1100 |
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On Mon, 2008-01-14 at 12:02 -0800, Christoph Lameter wrote: > On Sun, 13 Jan 2008, Andrea Arcangeli wrote: > > > About the locking perhaps I'm underestimating it, but by following the > > TLB flushing analogy, by simply clearing the shadow ptes (with kvm > > mmu_lock spinlock to avoid racing with other vcpu spte accesses of > > course) and flushing the shadow-pte after clearing the main linux pte, > > it should be enough to serialize against shadow-pte page faults that > > would call into get_user_pages. Flushing the host TLB before or after > > the shadow-ptes shouldn't matter. > > Hmmm... In most of the callsites we hold a writelock on mmap_sem right?
Not in unmap_mapping_range() afaik.
> > Comments welcome... especially from SGI/IBM/Quadrics and all other > > potential users of this functionality. > > > There are also certain details I'm uncertain about, like passing 'mm' > > to the lowlevel methods, my KVM usage of the invalidate_page() > > notifier for example only uses 'mm' for a BUG_ON for example: > > Passing mm is fine as long as mmap_sem is held.
Passing mm is always a good idea, regardless of the mmap_sem, it can be useful for lots of other things :-)
> > diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h > > --- a/include/asm-generic/pgtable.h > > +++ b/include/asm-generic/pgtable.h > > @@ -86,6 +86,7 @@ do { \ > > pte_t __pte; \ > > __pte = ptep_get_and_clear((__vma)->vm_mm, __address, __ptep); \ > > flush_tlb_page(__vma, __address); \ > > + mmu_notifier(invalidate_page, (__vma)->vm_mm, __address); \ > > __pte; \ > > }) > > #endif > > Hmmm... this is ptep_clear_flush? What about the other uses of > flush_tlb_page in asm-generic/pgtable.h and related uses in arch code? > (would help if your patches would mention the function name in the diff > headers)
Note that last I looked, a lot of these were stale. Might be time to resume my spring/summer cleaning of page table accessors...
> > +#define mmu_notifier(function, mm, args...) \ > > + do { \ > > + struct mmu_notifier *__mn; \ > > + struct hlist_node *__n; \ > > + \ > > + hlist_for_each_entry(__mn, __n, &(mm)->mmu_notifier, hlist) \ > > + if (__mn->ops->function) \ > > + __mn->ops->function(__mn, mm, args); \ > > + } while (0) > > Does this have to be inline? ptep_clear_flush will become quite big > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
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