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swiotlb: fix "x86: Don't panic if can not alloc buffer for swiotlb"

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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: ac2cbab21f ("x86: Don't panic if can not alloc buffer for swiotlb")

Reported-by: Elliott Mitchell <[email protected]>
Tested-by: Elliott Mitchell <[email protected]>
Signed-off-by: Stefano Stabellini <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Cc: [email protected]
Signed-off-by: Konrad Rzeszutek Wilk <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
This commit is contained in:
Stefano Stabellini 2020-10-26 17:02:14 -07:00 • committed by Greg Kroah-Hartman
commit 98901bff58
1 changed files with 5 additions and 1 deletions
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6
kernel/dma/swiotlb.c
View file

@ -230,6 +230,7 @@ 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();
@ -261,9 +262,11 @@ 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;
}
@ -361,6 +364,7 @@ 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();