On Fri, 23 Feb 2018 08:20:51 +0000 "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote: > > From: Alex Williamson > > Sent: Friday, February 23, 2018 6:59 AM > > > > On Thu, 1 Feb 2018 01:27:38 -0500 > > Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx> wrote: > > > > > 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 has a large number of > > mapped > > > IOVAs. This can be avoided by using the new IOTLB flushing interface. > > > > > > Cc: Alex Williamson <alex.williamson@xxxxxxxxxx> > > > Cc: Joerg Roedel <joro@xxxxxxxxxx> > > > Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx> > > > --- > > > > > > Changes from v4 (https://lkml.org/lkml/2018/1/31/153) > > > * Change return type from ssize_t back to size_t since we no longer > > > changing IOMMU API. Also update error handling logic accordingly. > > > * In unmap_unpin_fast(), also sync when failing to allocate entry. > > > * Some code restructuring and variable renaming. > > > > > > drivers/vfio/vfio_iommu_type1.c | 128 > > ++++++++++++++++++++++++++++++++++++---- > > > 1 file changed, 117 insertions(+), 11 deletions(-) > > > > > > diff --git a/drivers/vfio/vfio_iommu_type1.c > > b/drivers/vfio/vfio_iommu_type1.c > > > index e30e29a..6041530 100644 > > > --- a/drivers/vfio/vfio_iommu_type1.c > > > +++ b/drivers/vfio/vfio_iommu_type1.c > > > @@ -102,6 +102,13 @@ struct vfio_pfn { > > > atomic_t ref_count; > > > }; > > > > > > +struct vfio_regions { > > > + struct list_head list; > > > + dma_addr_t iova; > > > + phys_addr_t phys; > > > + size_t len; > > > +}; > > > + > > > #define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu) \ > > > (!list_empty(&iommu->domain_list)) > > > > > > @@ -648,11 +655,102 @@ static int > > vfio_iommu_type1_unpin_pages(void *iommu_data, > > > return i > npage ? npage : (i > 0 ? i : -EINVAL); > > > } > > > > > > +static long vfio_sync_unpin(struct vfio_dma *dma, struct vfio_domain > > *domain, > > > + struct list_head *regions) > > > +{ > > > + long unlocked = 0; > > > + struct vfio_regions *entry, *next; > > > + > > > + iommu_tlb_sync(domain->domain); > > > + > > > + list_for_each_entry_safe(entry, next, regions, list) { > > > + unlocked += vfio_unpin_pages_remote(dma, > > > + entry->iova, > > > + entry->phys >> > > PAGE_SHIFT, > > > + entry->len >> PAGE_SHIFT, > > > + false); > > > + list_del(&entry->list); > > > + kfree(entry); > > > + } > > > + > > > + cond_resched(); > > > + > > > + return unlocked; > > > +} > > > + > > > +/* > > > + * Generally, VFIO needs to unpin remote pages after each IOTLB flush. > > > + * Therefore, when using IOTLB flush sync interface, VFIO need to keep > > track > > > + * of these regions (currently using a list). > > > + * > > > + * This value specifies maximum number of regions for each IOTLB flush > > sync. > > > + */ > > > +#define VFIO_IOMMU_TLB_SYNC_MAX 512 > > > + > > > +static size_t unmap_unpin_fast(struct vfio_domain *domain, > > > + struct vfio_dma *dma, dma_addr_t *iova, > > > + size_t len, phys_addr_t phys, long *unlocked, > > > + struct list_head *unmapped_list, > > > + int *unmapped_cnt) > > > +{ > > > + size_t unmapped = 0; > > > + struct vfio_regions *entry = kzalloc(sizeof(*entry), GFP_KERNEL); > > > + > > > + if (entry) { > > > + unmapped = iommu_unmap_fast(domain->domain, *iova, > > len); > > > + > > > + if (!unmapped) { > > > + kfree(entry); > > > + } else { > > > + iommu_tlb_range_add(domain->domain, *iova, > > unmapped); > > > + entry->iova = *iova; > > > + entry->phys = phys; > > > + entry->len = unmapped; > > > + list_add_tail(&entry->list, unmapped_list); > > > + > > > + *iova += unmapped; > > > + (*unmapped_cnt)++; > > > + } > > > + } > > > + > > > + /* > > > + * Sync if the number of fast-unmap regions hits the limit > > > + * or in case of errors. > > > + */ > > > + if (*unmapped_cnt >= VFIO_IOMMU_TLB_SYNC_MAX > > || !unmapped) { > > > + *unlocked += vfio_sync_unpin(dma, domain, > > > + unmapped_list); > > > + *unmapped_cnt = 0; > > > + } > > I'm not sure why returning ZERO is treated as only unmap error > here, but if looking at __iommu_unmap clearly there are other > error codes returned also. I know it's not introduced by this > patch but Alex, was it deliberately implemented such way under > any assumption or a typo? iommu_unmap() returns a size_t, an unsigned type. Suravee has another patch in the iommu space to correct that function from trying to return -errno. Thanks, Alex
