On Wed, Apr 03, 2019 at 11:34:12AM -0600, Khalid Aziz wrote: > From: Julian Stecklina <[email protected]> > > Only the xpfo_kunmap call that needs to actually unmap the page > needs to be serialized. We need to be careful to handle the case, > where after the atomic decrement of the mapcount, a xpfo_kmap > increased the mapcount again. In this case, we can safely skip > modifying the page table. > > Model-checked with up to 4 concurrent callers with Spin. > > Signed-off-by: Julian Stecklina <[email protected]> > Signed-off-by: Khalid Aziz <[email protected]> > Cc: Khalid Aziz <[email protected]> > Cc: [email protected] > Cc: [email protected] > Cc: Vasileios P. Kemerlis <[email protected]> > Cc: Juerg Haefliger <[email protected]> > Cc: Tycho Andersen <[email protected]> > Cc: Marco Benatto <[email protected]> > Cc: David Woodhouse <[email protected]> > --- > include/linux/xpfo.h | 24 +++++++++++++++--------- > 1 file changed, 15 insertions(+), 9 deletions(-) > > diff --git a/include/linux/xpfo.h b/include/linux/xpfo.h > index 2318c7eb5fb7..37e7f52fa6ce 100644 > --- a/include/linux/xpfo.h > +++ b/include/linux/xpfo.h > @@ -61,6 +61,7 @@ static inline void xpfo_kmap(void *kaddr, struct page *page) > static inline void xpfo_kunmap(void *kaddr, struct page *page) > { > unsigned long flags; > + bool flush_tlb = false; > > if (!static_branch_unlikely(&xpfo_inited)) > return; > @@ -72,18 +73,23 @@ static inline void xpfo_kunmap(void *kaddr, struct page > *page) > * The page is to be allocated back to user space, so unmap it from > * the kernel, flush the TLB and tag it as a user page. > */ > - spin_lock_irqsave(&page->xpfo_lock, flags); > - > if (atomic_dec_return(&page->xpfo_mapcount) == 0) { > -#ifdef CONFIG_XPFO_DEBUG > - WARN_ON(PageXpfoUnmapped(page)); > -#endif > - SetPageXpfoUnmapped(page); > - set_kpte(kaddr, page, __pgprot(0)); > - xpfo_flush_kernel_tlb(page, 0); > + spin_lock_irqsave(&page->xpfo_lock, flags); > + > + /* > + * In the case, where we raced with kmap after the > + * atomic_dec_return, we must not nuke the mapping. > + */ > + if (atomic_read(&page->xpfo_mapcount) == 0) { > + SetPageXpfoUnmapped(page); > + set_kpte(kaddr, page, __pgprot(0)); > + flush_tlb = true; > + } > + spin_unlock_irqrestore(&page->xpfo_lock, flags); > } > > - spin_unlock_irqrestore(&page->xpfo_lock, flags); > + if (flush_tlb) > + xpfo_flush_kernel_tlb(page, 0); > }
This doesn't help with the TLB invalidation issue, AFAICT this is still completely buggered. kunmap_atomic() can be called from IRQ context. _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
