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Commit 02ee0fe6 authored by Stefano Stabellini's avatar Stefano Stabellini Committed by Greg Kroah-Hartman
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swiotlb: fix "x86: Don't panic if can not alloc buffer for swiotlb" 



commit e9696d259d0fb5d239e8c28ca41089838ea76d13 upstream.

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.

Fixes: ac2cbab2 ("x86: Don't panic if can not alloc buffer for swiotlb")

Reported-by: default avatarElliott Mitchell <ehem+xen@m5p.com>
Tested-by: default avatarElliott Mitchell <ehem+xen@m5p.com>
Signed-off-by: default avatarStefano Stabellini <stefano.stabellini@xilinx.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent ebe96a42

kernel/dma/swiotlb.c

+5 −1
Original line number Diff line number Diff line
@@ -239,6 +239,7 @@ 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();
@@ -270,9 +271,11 @@ 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;

}
@@ -376,6 +379,7 @@ 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();