On Mon, 6 Nov 2023, Mikulas Patocka wrote: > From: Keith Busch <kbusch@xxxxxxxxxx> > > 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@xxxxxxxxxxxxxxxxxxxxxx> > Link: https://lore.kernel.org/stable/ZTNH0qtmint%2FzLJZ@mail-itl/ [1] > Tested-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx> > Suggested-by: Christoph Hellwig <hch@xxxxxx> > Cc: stable@xxxxxxxxxxxxxxx > Signed-off-by: Keith Busch <kbusch@xxxxxxxxxx> > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx> > --- > drivers/xen/swiotlb-xen.c | 1 + > 1 file changed, 1 insertion(+) > > Index: linux-stable/drivers/xen/swiotlb-xen.c > =================================================================== > --- linux-stable.orig/drivers/xen/swiotlb-xen.c 2023-11-03 17:57:18.000000000 +0100 > +++ linux-stable/drivers/xen/swiotlb-xen.c 2023-11-06 15:30:59.000000000 +0100 > @@ -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, > };
