On Mon, Nov 06, 2023 at 03:59:40PM +0100, Mikulas Patocka wrote: > There's a bug that when using the XEN hypervisor with dm-crypt 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. > > [1] https://lore.kernel.org/stable/ZTNH0qtmint%2FzLJZ@mail-itl/ This should be a "Link:" tag. > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> > Reported-by: Marek Marczykowski-G'orecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx> > Tested-by: Marek Marczykowski-G'orecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx> > Suggested-by: Keith Busch <kbusch@xxxxxxxxxx> I was about to send the same thing. I did a little more than suggest this: it's is the very patch I wrote for testing, minus the redundant nvme bits! But since you already have a commit message for it... Acked-by: Keith Busch <kbusch@xxxxxxxxxx> > Suggested-by: Christoph Hellwig <hch@xxxxxx> > Cc: stable@xxxxxxxxxxxxxxx > > --- > 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, > };
