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 (e.g. GPUs). This could also cause IOTLB invalidate time-out issue on AMD IOMMU with certain dGPUs.
This can be avoided by using the new IOTLB flushing interface. Cc: Alex Williamson <alex.william...@redhat.com> Cc: Joerg Roedel <jroe...@suse.de> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpa...@amd.com> --- Changes from V2: (https://lkml.org/lkml/2017/12/27/43) * In vfio_unmap_unpin(), fallback to use slow IOTLB flush when fast IOTLB flush fails (per Alex). * Do not adopt fast IOTLB flush in map_try_harder(). * Submit VFIO and AMD IOMMU patches separately. drivers/vfio/vfio_iommu_type1.c | 98 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 98 insertions(+) diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c index e30e29a..5c40b00 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)) @@ -479,6 +486,36 @@ static long vfio_unpin_pages_remote(struct vfio_dma *dma, dma_addr_t iova, 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 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; +} + static int vfio_pin_page_external(struct vfio_dma *dma, unsigned long vaddr, unsigned long *pfn_base, bool do_accounting) { @@ -648,12 +685,40 @@ static int vfio_iommu_type1_unpin_pages(void *iommu_data, return i > npage ? npage : (i > 0 ? i : -EINVAL); } +static size_t try_unmap_unpin_fast(struct vfio_domain *domain, dma_addr_t iova, + size_t len, phys_addr_t phys, + struct list_head *unmapped_regions) +{ + struct vfio_regions *entry; + size_t unmapped; + + entry = kzalloc(sizeof(*entry), GFP_KERNEL); + if (!entry) + return -ENOMEM; + + unmapped = iommu_unmap_fast(domain->domain, iova, len); + if (WARN_ON(!unmapped)) { + kfree(entry); + return -EINVAL; + } + + iommu_tlb_range_add(domain->domain, iova, unmapped); + entry->iova = iova; + entry->phys = phys; + entry->len = unmapped; + list_add_tail(&entry->list, unmapped_regions); + 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_regions; + bool use_fastpath = true; long unlocked = 0; + int cnt = 0; if (!dma->size) return 0; @@ -661,6 +726,8 @@ 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_regions); + /* * We use the IOMMU to track the physical addresses, otherwise we'd * need a much more complicated tracking system. Unfortunately that @@ -698,6 +765,33 @@ static long vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma, break; } + /* + * First, try to use fast unmap/unpin. In case of failure, + * sync upto the current point, and continue the slow + * unmap/unpin path. + */ + if (use_fastpath) { + unmapped = try_unmap_unpin_fast(domain, iova, + len, phys, + &unmapped_regions); + if (unmapped > 0) { + iova += unmapped; + cnt++; + } else { + use_fastpath = false; + } + + if (cnt >= VFIO_IOMMU_TLB_SYNC_MAX || !use_fastpath) { + unlocked += vfio_sync_unpin(dma, domain, + &unmapped_regions); + cnt = 0; + } + + if (use_fastpath) + continue; + } + + /* Slow unmap/unpin path */ unmapped = iommu_unmap(domain->domain, iova, len); if (WARN_ON(!unmapped)) break; @@ -712,6 +806,10 @@ static long vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma, } dma->iommu_mapped = false; + + if (cnt) + unlocked += vfio_sync_unpin(dma, domain, &unmapped_regions); + if (do_accounting) { vfio_lock_acct(dma->task, -unlocked, NULL); return 0; -- 1.8.3.1 _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
