[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID:
<SN6PR02MB4157828120FB7D3408CEC991D4572@SN6PR02MB4157.namprd02.prod.outlook.com>
Date: Wed, 21 Feb 2024 23:39:29 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Will Deacon <will@...nel.org>, "linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>
CC: "kernel-team@...roid.com" <kernel-team@...roid.com>,
"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>, Christoph Hellwig
<hch@....de>, Marek Szyprowski <m.szyprowski@...sung.com>, Robin Murphy
<robin.murphy@....com>, Petr Tesarik <petr.tesarik1@...wei-partners.com>,
Dexuan Cui <decui@...rosoft.com>, Nicolin Chen <nicolinc@...dia.com>
Subject: RE: [PATCH v4 5/5] iommu/dma: Force swiotlb_max_mapping_size on an
untrusted device
From: Will Deacon <will@...nel.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@...dia.com>
> Link: https://lore.kernel.org/all/ee51a3a5c32cf885b18f6416171802669f4a718a.1707851466.git.nicolinc@nvidia.com/
> Signed-off-by: Will Deacon <will@...nel.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
Powered by blists - more mailing lists