This is a note to let you know that I've just added the patch titled
swiotlb: fix "x86: Don't panic if can not alloc buffer for swiotlb"
to the 5.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
swiotlb-fix-x86-don-t-panic-if-can-not-alloc-buffer-for-swiotlb.patch
and it can be found in the queue-5.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e9696d259d0fb5d239e8c28ca41089838ea76d13 Mon Sep 17 00:00:00 2001
From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
Date: Mon, 26 Oct 2020 17:02:14 -0700
Subject: swiotlb: fix "x86: Don't panic if can not alloc buffer for swiotlb"
From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
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: ac2cbab21f31 ("x86: Don't panic if can not alloc buffer for swiotlb")
Reported-by: Elliott Mitchell <ehem+xen@xxxxxxx>
Tested-by: Elliott Mitchell <ehem+xen@xxxxxxx>
Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/dma/swiotlb.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -231,6 +231,7 @@ int __init swiotlb_init_with_tbl(char *t
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, un
io_tlb_orig_addr[i] = INVALID_PHYS_ADDR;
}
io_tlb_index = 0;
+ no_iotlb_memory = false;
swiotlb_print_info();
Patches currently in stable-queue which might be from stefano.stabellini@xxxxxxxxxx are
queue-5.9/swiotlb-fix-x86-don-t-panic-if-can-not-alloc-buffer-for-swiotlb.patch
