6.1-stable review patch. If anyone has any objections, please let me know.
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From: Keith Busch kbusch@kernel.org
commit bff2a2d453a1b683378b4508b86b84389f551a00 upstream.
There's a bug that when using the XEN hypervisor with bios with large multi-page bio vectors on NVMe, the kernel deadlocks [1].
The deadlocks are caused by inability to map a large bio vector - dma_map_sgtable always returns an error, this gets propagated to the block layer as BLK_STS_RESOURCE and the block layer retries the request indefinitely.
XEN uses the swiotlb framework to map discontiguous pages into contiguous runs that are submitted to the PCIe device. The swiotlb framework has a limitation on the length of a mapping - this needs to be announced with the max_mapping_size method to make sure that the hardware drivers do not create larger mappings.
Without max_mapping_size, the NVMe block driver would create large mappings that overrun the maximum mapping size.
Reported-by: Marek Marczykowski-Górecki marmarek@invisiblethingslab.com Link: https://lore.kernel.org/stable/ZTNH0qtmint%2FzLJZ@mail-itl/ [1] Tested-by: Marek Marczykowski-Górecki marmarek@invisiblethingslab.com Suggested-by: Christoph Hellwig hch@lst.de Cc: stable@vger.kernel.org Signed-off-by: Keith Busch kbusch@kernel.org Signed-off-by: Mikulas Patocka mpatocka@redhat.com Acked-by: Stefano Stabellini sstabellini@kernel.org Reviewed-by: Christoph Hellwig hch@lst.de Link: https://lore.kernel.org/r/151bef41-e817-aea9-675-a35fdac4ed@redhat.com Signed-off-by: Juergen Gross jgross@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/xen/swiotlb-xen.c | 1 + 1 file changed, 1 insertion(+)
--- a/drivers/xen/swiotlb-xen.c +++ b/drivers/xen/swiotlb-xen.c @@ -405,4 +405,5 @@ const struct dma_map_ops xen_swiotlb_dma .get_sgtable = dma_common_get_sgtable, .alloc_pages = dma_common_alloc_pages, .free_pages = dma_common_free_pages, + .max_mapping_size = swiotlb_max_mapping_size, };