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.william...@redhat.com> Cc: Joerg Roedel <j...@8bytes.org> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpa...@amd.com> --- 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; + } + + return unmapped; +} + +static size_t unmap_unpin_slow(struct vfio_domain *domain, + struct vfio_dma *dma, dma_addr_t *iova, + size_t len, phys_addr_t phys, + long *unlocked) +{ + size_t unmapped = iommu_unmap(domain->domain, *iova, len); + + if (unmapped) { + *unlocked += vfio_unpin_pages_remote(dma, *iova, + phys >> PAGE_SHIFT, + unmapped >> PAGE_SHIFT, + false); + *iova += unmapped; + cond_resched(); + } + return unmapped; +} + static long vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma, bool do_accounting) { dma_addr_t iova = dma->iova, end = dma->iova + dma->size; struct vfio_domain *domain, *d; + struct list_head unmapped_region_list; + int unmapped_region_cnt = 0; long unlocked = 0; if (!dma->size) @@ -661,6 +759,8 @@ static long vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma, if (!IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu)) return 0; + INIT_LIST_HEAD(&unmapped_region_list); + /* * We use the IOMMU to track the physical addresses, otherwise we'd * need a much more complicated tracking system. Unfortunately that @@ -698,20 +798,26 @@ static long vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma, break; } - unmapped = iommu_unmap(domain->domain, iova, len); - if (WARN_ON(!unmapped)) - break; - - unlocked += vfio_unpin_pages_remote(dma, iova, - phys >> PAGE_SHIFT, - unmapped >> PAGE_SHIFT, - false); - iova += unmapped; - - cond_resched(); + /* + * First, try to use fast unmap/unpin. In case of failure, + * switch to slow unmap/unpin path. + */ + unmapped = unmap_unpin_fast(domain, dma, &iova, len, phys, + &unlocked, &unmapped_region_list, + &unmapped_region_cnt); + if (!unmapped) { + unmapped = unmap_unpin_slow(domain, dma, &iova, len, + phys, &unlocked); + if (WARN_ON(!unmapped)) + break; + } } dma->iommu_mapped = false; + + if (unmapped_region_cnt) + unlocked += vfio_sync_unpin(dma, domain, &unmapped_region_list); + if (do_accounting) { vfio_lock_acct(dma->task, -unlocked, NULL); return 0; -- 1.8.3.1
