On Mon, Oct 26, 2020 at 05:02:14PM -0700, Stefano Stabellini wrote: > From: Stefano Stabellini <stefano.stabell...@xilinx.com> > > kernel/dma/swiotlb.c:swiotlb_init gets called first and tries to > allocate a buffer for the swiotlb. It does so by calling > > memblock_alloc_low(PAGE_ALIGN(bytes), PAGE_SIZE); > > If the allocation must fail, no_iotlb_memory is set. > > > Later during initialization swiotlb-xen comes in > (drivers/xen/swiotlb-xen.c:xen_swiotlb_init) and given that io_tlb_start > is != 0, it thinks the memory is ready to use when actually it is not. > > When the swiotlb is actually needed, swiotlb_tbl_map_single gets called > and since no_iotlb_memory is set the kernel panics. > > Instead, if swiotlb-xen.c:xen_swiotlb_init knew the swiotlb hadn't been > initialized, it would do the initialization itself, which might still > succeed. > > > Fix the panic by setting io_tlb_start to 0 on swiotlb initialization > failure, and also by setting no_iotlb_memory to false on swiotlb > initialization success. > > Signed-off-by: Stefano Stabellini <stefano.stabell...@xilinx.com> > > > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c > index c19379fabd20..9924214df60a 100644 > --- a/kernel/dma/swiotlb.c > +++ b/kernel/dma/swiotlb.c > @@ -231,6 +231,7 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long > nslabs, int verbose) > io_tlb_orig_addr[i] = INVALID_PHYS_ADDR; > } > io_tlb_index = 0; > + no_iotlb_memory = false; > > if (verbose) > swiotlb_print_info(); > @@ -262,9 +263,11 @@ swiotlb_init(int verbose) > if (vstart && !swiotlb_init_with_tbl(vstart, io_tlb_nslabs, verbose)) > return; > > - if (io_tlb_start) > + if (io_tlb_start) { > memblock_free_early(io_tlb_start, > PAGE_ALIGN(io_tlb_nslabs << IO_TLB_SHIFT)); > + io_tlb_start = 0; > + } > pr_warn("Cannot allocate buffer"); > no_iotlb_memory = true; > } > @@ -362,6 +365,7 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long > nslabs) > io_tlb_orig_addr[i] = INVALID_PHYS_ADDR; > } > io_tlb_index = 0; > + no_iotlb_memory = false; > > swiotlb_print_info(); >
As the person who first found this and then confirmed this fixes a bug: Tested-by: Elliott Mitchell <ehem+...@m5p.com> -- (\___(\___(\______ --=> 8-) EHM <=-- ______/)___/)___/) \BS ( | ehem+sig...@m5p.com PGP 87145445 | ) / \_CS\ | _____ -O #include <stddisclaimer.h> O- _____ | / _/ 8A19\___\_|_/58D2 7E3D DDF4 7BA6 <-PGP-> 41D1 B375 37D0 8714\_|_/___/5445