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Commit e9696d25 authored by Stefano Stabellini's avatar Stefano Stabellini Committed by Konrad Rzeszutek Wilk
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swiotlb: fix "x86: Don't panic if can not alloc buffer for swiotlb"



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>
parent 3650b228
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