Messages in this thread | | | Date | Wed, 14 Feb 2024 16:41:38 +0000 | From | Will Deacon <> | Subject | Re: [PATCH v1 0/2] nvme-pci: Fix dma-iommu mapping failures when PAGE_SIZE=64KB |
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Hi Nicolin,
On Tue, Feb 13, 2024 at 01:53:55PM -0800, Nicolin Chen wrote: > It's observed that an NVME device is causing timeouts when Ubuntu boots > with a kernel configured with PAGE_SIZE=64KB due to failures in swiotlb: > 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 > > An NVME device under a PCIe bus can be behind an IOMMU, so dma mappings > going through dma-iommu might be also redirected to swiotlb allocations. > Similar to dma_direct_max_mapping_size(), dma-iommu should implement its > dma_map_ops->max_mapping_size to return swiotlb_max_mapping_size() too. > > Though an iommu_dma_max_mapping_size() is a must, it alone can't fix the > issue. The swiotlb_max_mapping_size() returns 252KB, calculated from the > default pool 256KB subtracted by min_align_mask NVME_CTRL_PAGE_SIZE=4KB, > while dma-iommu can roundup a 252KB mapping to 256KB at its "alloc_size" > when PAGE_SIZE=64KB via iova->granule that is often set to PAGE_SIZE. So > this mismatch between NVME_CTRL_PAGE_SIZE=4KB and PAGE_SIZE=64KB results > in a similar failure, though its signature has a fixed size "256KB": > systemd[1]: Started Journal Service. > => nvme 0000:00:01.0: swiotlb buffer is full (sz: 262144 bytes), total 32768 (slots), used 128 (slots) > note: journal-offline[392] exited with irqs disabled > note: journal-offline[392] exited with preempt_count 1 > > Both failures above occur to NVME behind IOMMU when PAGE_SIZE=64KB. They > were likely introduced for the security feature by: > commit 82612d66d51d ("iommu: Allow the dma-iommu api to use bounce buffers"), > > So, this series bundles two fixes together against that. They should be > taken at the same time to entirely fix the mapping failures.
It's a bit of a shot in the dark, but I've got a pending fix to some of the alignment handling in swiotlb. It would be interesting to know if patch 1 has any impact at all on your NVME allocations:
https://lore.kernel.org/r/20240205190127.20685-1-will@kernel.org
Cheers,
Will
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