Messages in this thread | | | From | Michael Kelley <> | Subject | RE: [PATCH v4 5/5] iommu/dma: Force swiotlb_max_mapping_size on an untrusted device | Date | Wed, 21 Feb 2024 23:39:29 +0000 |
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From: Will Deacon <will@kernel.org> Sent: Wednesday, February 21, 2024 3:35 AM > > The swiotlb does not support a mapping size > swiotlb_max_mapping_size(). > On the other hand, with a 64KB PAGE_SIZE configuration, it's observed that > an NVME device can map a size between 300KB~512KB, which certainly failed > the swiotlb mappings, though the default pool of swiotlb has many slots: > systemd[1]: Started Journal Service. > => nvme 0000:00:01.0: swiotlb buffer is full (sz: 327680 bytes), total 32768 > (slots), used 32 (slots) > note: journal-offline[392] exited with irqs disabled > note: journal-offline[392] exited with preempt_count 1 > > Call trace: > [ 3.099918] swiotlb_tbl_map_single+0x214/0x240 > [ 3.099921] iommu_dma_map_page+0x218/0x328 > [ 3.099928] dma_map_page_attrs+0x2e8/0x3a0 > [ 3.101985] nvme_prep_rq.part.0+0x408/0x878 [nvme] > [ 3.102308] nvme_queue_rqs+0xc0/0x300 [nvme] > [ 3.102313] blk_mq_flush_plug_list.part.0+0x57c/0x600 > [ 3.102321] blk_add_rq_to_plug+0x180/0x2a0 > [ 3.102323] blk_mq_submit_bio+0x4c8/0x6b8 > [ 3.103463] __submit_bio+0x44/0x220 > [ 3.103468] submit_bio_noacct_nocheck+0x2b8/0x360 > [ 3.103470] submit_bio_noacct+0x180/0x6c8 > [ 3.103471] submit_bio+0x34/0x130 > [ 3.103473] ext4_bio_write_folio+0x5a4/0x8c8 > [ 3.104766] mpage_submit_folio+0xa0/0x100 > [ 3.104769] mpage_map_and_submit_buffers+0x1a4/0x400 > [ 3.104771] ext4_do_writepages+0x6a0/0xd78 > [ 3.105615] ext4_writepages+0x80/0x118 > [ 3.105616] do_writepages+0x90/0x1e8 > [ 3.105619] filemap_fdatawrite_wbc+0x94/0xe0 > [ 3.105622] __filemap_fdatawrite_range+0x68/0xb8 > [ 3.106656] file_write_and_wait_range+0x84/0x120 > [ 3.106658] ext4_sync_file+0x7c/0x4c0 > [ 3.106660] vfs_fsync_range+0x3c/0xa8 > [ 3.106663] do_fsync+0x44/0xc0 > > Since untrusted devices might go down the swiotlb pathway with dma-iommu, > these devices should not map a size larger than swiotlb_max_mapping_size. > > To fix this bug, add iommu_dma_max_mapping_size() for untrusted devices to > take into account swiotlb_max_mapping_size() v.s. iova_rcache_range() from > the iommu_dma_opt_mapping_size(). > > Fixes: 82612d66d51d ("iommu: Allow the dma-iommu api to use bounce buffers") > Signed-off-by: Nicolin Chen <nicolinc@nvidia.com> > Link: https://lore.kernel.org/all/ee51a3a5c32cf885b18f6416171802669f4a718a.1707851466.git.nicolinc@nvidia.com/ > Signed-off-by: Will Deacon <will@kernel.org> > --- > drivers/iommu/dma-iommu.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index 50ccc4f1ef81..7d1a20da6d94 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -1706,6 +1706,13 @@ static size_t > iommu_dma_opt_mapping_size(void) > return iova_rcache_range(); > } > > +static size_t iommu_dma_max_mapping_size(struct device *dev) > +{ > + if (is_swiotlb_active(dev) && dev_is_untrusted(dev)) > + return swiotlb_max_mapping_size(dev); > + return SIZE_MAX; > +} > +
In this [1] email, Nicolin had a version of this function that incorporated the IOMMU granule. For granules bigger than 4K, I think that's needed so that when IOMMU code sets the swiotlb alloc_align_mask to the IOMMU granule - 1, the larger offset plus the size won't exceed the max number of slots. swiotlb_max_mapping_size() by itself may return a value that's too big when alloc_align_mask is used.
Michael
[1] https://lore.kernel.org/linux-iommu/SN6PR02MB415727E61B5295C259CCB268D4512@SN6PR02MB4157.namprd02.prod.outlook.com/T/#m14dd359c5a4dd13e6cb0c35cf94f8d746257ae48
> static const struct dma_map_ops iommu_dma_ops = { > .flags = DMA_F_PCI_P2PDMA_SUPPORTED, > .alloc = iommu_dma_alloc, > @@ -1728,6 +1735,7 @@ static const struct dma_map_ops iommu_dma_ops = { > .unmap_resource = iommu_dma_unmap_resource, > .get_merge_boundary = iommu_dma_get_merge_boundary, > .opt_mapping_size = iommu_dma_opt_mapping_size, > + .max_mapping_size = iommu_dma_max_mapping_size, > }; > > /* > -- > 2.44.0.rc0.258.g7320e95886-goog
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