This is a pretty massive memory leak, anyone @Intel care? Thanks, Alex
On Sat, 2013-06-15 at 10:27 -0600, Alex Williamson wrote: > At best the current code only seems to free the leaf pagetables and > the root. If you're unlucky enough to have a large gap (like any > QEMU guest with more than 3G of memory), only the first chunk of leaf > pagetables are freed (plus the root). This is a massive memory leak. > This patch re-writes the pagetable freeing function to use a > recursive algorithm and manages to not only free all the pagetables, > but does it without any apparent performance loss versus the current > broken version. > > Signed-off-by: Alex Williamson <alex.william...@redhat.com> > Cc: sta...@vger.kernel.org > --- > > Suggesting for stable, would like to see some soak time, but it's > hard to imagine this being any worse than the current code. > > This likely also affects device domains, but the current code does > ok at freeing individual leaf pagetables and driver domains would > only get a full pruning if the driver or device is removed. > > Some test programs: > https://github.com/awilliam/tests/blob/master/kvm-huge-guest-test.c > https://github.com/awilliam/tests/blob/master/vfio-huge-guest-test.c > > Both of these simulate a large guest on a small host system. They > mmap 4G of memory and map it across a large address space just like > QEMU would (aside from re-using the same mmap across multiple IOVAs). > On existing code the vfio version (w/o a KVM memory slot limit) will > leak over 1G of pagetables per run. > > drivers/iommu/intel-iommu.c | 72 > +++++++++++++++++++++---------------------- > 1 file changed, 35 insertions(+), 37 deletions(-) > > diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c > index eec0d3e..15e9b57 100644 > --- a/drivers/iommu/intel-iommu.c > +++ b/drivers/iommu/intel-iommu.c > @@ -890,56 +890,54 @@ static int dma_pte_clear_range(struct dmar_domain > *domain, > return order; > } > > +static void dma_pte_free_level(struct dmar_domain *domain, int level, > + struct dma_pte *pte, unsigned long pfn, > + unsigned long start_pfn, unsigned long last_pfn) > +{ > + pfn = max(start_pfn, pfn); > + pte = &pte[pfn_level_offset(pfn, level)]; > + > + do { > + unsigned long level_pfn; > + struct dma_pte *level_pte; > + > + if (!dma_pte_present(pte) || dma_pte_superpage(pte)) > + goto next; > + > + level_pfn = pfn & level_mask(level - 1); > + level_pte = phys_to_virt(dma_pte_addr(pte)); > + > + if (level > 2) > + dma_pte_free_level(domain, level - 1, level_pte, > + level_pfn, start_pfn, last_pfn); > + > + /* If range covers entire pagetable, free it */ > + if (!(start_pfn > level_pfn || > + last_pfn < level_pfn + level_size(level))) { > + dma_clear_pte(pte); > + domain_flush_cache(domain, pte, sizeof(*pte)); > + free_pgtable_page(level_pte); > + } > +next: > + pfn += level_size(level); > + } while (!first_pte_in_page(++pte) && pfn <= last_pfn); > +} > + > /* free page table pages. last level pte should already be cleared */ > static void dma_pte_free_pagetable(struct dmar_domain *domain, > unsigned long start_pfn, > unsigned long last_pfn) > { > int addr_width = agaw_to_width(domain->agaw) - VTD_PAGE_SHIFT; > - struct dma_pte *first_pte, *pte; > - int total = agaw_to_level(domain->agaw); > - int level; > - unsigned long tmp; > - int large_page = 2; > > BUG_ON(addr_width < BITS_PER_LONG && start_pfn >> addr_width); > BUG_ON(addr_width < BITS_PER_LONG && last_pfn >> addr_width); > BUG_ON(start_pfn > last_pfn); > > /* We don't need lock here; nobody else touches the iova range */ > - level = 2; > - while (level <= total) { > - tmp = align_to_level(start_pfn, level); > - > - /* If we can't even clear one PTE at this level, we're done */ > - if (tmp + level_size(level) - 1 > last_pfn) > - return; > - > - do { > - large_page = level; > - first_pte = pte = dma_pfn_level_pte(domain, tmp, level, > &large_page); > - if (large_page > level) > - level = large_page + 1; > - if (!pte) { > - tmp = align_to_level(tmp + 1, level + 1); > - continue; > - } > - do { > - if (dma_pte_present(pte)) { > - > free_pgtable_page(phys_to_virt(dma_pte_addr(pte))); > - dma_clear_pte(pte); > - } > - pte++; > - tmp += level_size(level); > - } while (!first_pte_in_page(pte) && > - tmp + level_size(level) - 1 <= last_pfn); > + dma_pte_free_level(domain, agaw_to_level(domain->agaw), > + domain->pgd, 0, start_pfn, last_pfn); > > - domain_flush_cache(domain, first_pte, > - (void *)pte - (void *)first_pte); > - > - } while (tmp && tmp + level_size(level) - 1 <= last_pfn); > - level++; > - } > /* free pgd */ > if (start_pfn == 0 && last_pfn == DOMAIN_MAX_PFN(domain->gaw)) { > free_pgtable_page(domain->pgd); > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
