On Fri, 17 Nov 2017 14:51:52 -0700 Alex Williamson <[email protected]> wrote:
> On Fri, 17 Nov 2017 15:11:19 -0600 > Suravee Suthikulpanit <[email protected]> wrote: > > > From: Suravee Suthikulpanit <[email protected]> > > > > VFIO IOMMU type1 currently upmaps IOVA pages synchronously, which requires > > IOTLB flushing for every unmapping. This results in large IOTLB flushing > > overhead when handling pass-through devices with a large number of mapped > > IOVAs (e.g. GPUs). > > Of course the type of device is really irrelevant, QEMU maps the entire > VM address space for any assigned device. > > > This can be avoided by using the new IOTLB flushing interface. > > > > Cc: Alex Williamson <[email protected]> > > Cc: Joerg Roedel <[email protected]> > > Signed-off-by: Suravee Suthikulpanit <[email protected]> > > --- > > drivers/vfio/vfio_iommu_type1.c | 12 +++++++++--- > > 1 file changed, 9 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/vfio/vfio_iommu_type1.c > > b/drivers/vfio/vfio_iommu_type1.c > > index 92155cc..28a7ab6 100644 > > --- a/drivers/vfio/vfio_iommu_type1.c > > +++ b/drivers/vfio/vfio_iommu_type1.c > > @@ -698,10 +698,12 @@ static long vfio_unmap_unpin(struct vfio_iommu > > *iommu, struct vfio_dma *dma, > > break; > > } > > > > - unmapped = iommu_unmap(domain->domain, iova, len); > > + unmapped = iommu_unmap_fast(domain->domain, iova, len); > > if (WARN_ON(!unmapped)) > > break; > > > > + iommu_tlb_range_add(domain->domain, iova, len); > > + > > We should only add @unmapped, not @len, right? Actually, the problems are deeper than that, if we can't guarantee that the above iommu_unmap_fast has removed the iommu mapping, then we can't do the unpin below as that would potentially allow the device access to unknown memory. Thus, to support this, the unpinning would need to be pushed until after the sync and we therefore need some mechanism of remembering the phys addresses that we've unmapped. Thanks, Alex > > unlocked += vfio_unpin_pages_remote(dma, iova, > > phys >> PAGE_SHIFT, > > unmapped >> PAGE_SHIFT, > > @@ -710,6 +712,7 @@ static long vfio_unmap_unpin(struct vfio_iommu *iommu, > > struct vfio_dma *dma, > > > > cond_resched(); > > } > > + iommu_tlb_sync(domain->domain); > > > > dma->iommu_mapped = false; > > if (do_accounting) { > > @@ -884,8 +887,11 @@ static int map_try_harder(struct vfio_domain *domain, > > dma_addr_t iova, > > break; > > } > > > > - for (; i < npage && i > 0; i--, iova -= PAGE_SIZE) > > - iommu_unmap(domain->domain, iova, PAGE_SIZE); > > + for (; i < npage && i > 0; i--, iova -= PAGE_SIZE) { > > + iommu_unmap_fast(domain->domain, iova, PAGE_SIZE); > > + iommu_tlb_range_add(domain->domain, iova, PAGE_SIZE); > > + } > > + iommu_tlb_sync(domain->domain); > > > > return ret; > > } > > _______________________________________________ > iommu mailing list > [email protected] > https://lists.linuxfoundation.org/mailman/listinfo/iommu
