mbox series

[v2,0/2] Fix boot failure due to misaligned DMA buffer

Message ID cover.1730988601.git.namcao@linutronix.de
Headers show
Series Fix boot failure due to misaligned DMA buffer | expand

Message

Nam Cao Nov. 7, 2024, 3:01 p.m. UTC 
Hi,

We observed the following sporadic boot failure while booting from MMC
device:

=> boot
CACHE: Misaligned operation at range [9efa25f8, 9efa27f8]
CACHE: Misaligned operation at range [9efa25f8, 9efa27f8]
CACHE: Misaligned operation at range [9efa25f8, 9efa27f8]
CACHE: Misaligned operation at range [9efa25f8, 9efa27f8]
** Booting bootflow 'mmc@2194000.bootdev.part_1' with extlinux
Ignoring unknown command: �D���D��
Boot failed (err=-14)

The reason is because while allocating buffer to read a file from MMC,
alignment of 1 byte is used. Thus, the buffer doesn't work for performing
DMA, and garbage data is read.

While looking at this issue, I also noticed that if no alignment specified
(align=0) then fs_read_alloc() is documented to use the default. But the
default is no alignment. Therefore, other users of fs_read_alloc() which
specify align=0 may be broken as well.

The first patch changes extlinux_read_bootflow() to use proper buffer
alignment for DMA.

The second patch changes the default alignment of fs_read_alloc() to be
DMA-suitable, to fix other potential bugs.

Nam Cao (2):
  boot: extlinux: Fix unaligned buffer for reading data from file system
  fs: Use ARCH_DMA_MINALIGN as default alignment for fs_read_alloc()

 boot/bootmeth_extlinux.c | 3 ++-
 fs/fs.c                  | 4 ++++
 include/fs.h             | 2 +-
 3 files changed, 7 insertions(+), 2 deletions(-)

Comments

Tony Dinh Nov. 8, 2024, 1:27 a.m. UTC | #1 
Hi Nam,


On Thu, Nov 7, 2024 at 1:53 PM Nam Cao <namcao@linutronix.de> wrote:
>
> Hi,
>
> We observed the following sporadic boot failure while booting from MMC
> device:
>
> => boot
> CACHE: Misaligned operation at range [9efa25f8, 9efa27f8]
> CACHE: Misaligned operation at range [9efa25f8, 9efa27f8]
> CACHE: Misaligned operation at range [9efa25f8, 9efa27f8]
> CACHE: Misaligned operation at range [9efa25f8, 9efa27f8]
> ** Booting bootflow 'mmc@2194000.bootdev.part_1' with extlinux
> Ignoring unknown command: �D���D��
> Boot failed (err=-14)
>
> The reason is because while allocating buffer to read a file from MMC,
> alignment of 1 byte is used. Thus, the buffer doesn't work for performing
> DMA, and garbage data is read.
>
> While looking at this issue, I also noticed that if no alignment specified
> (align=0) then fs_read_alloc() is documented to use the default. But the
> default is no alignment. Therefore, other users of fs_read_alloc() which
> specify align=0 may be broken as well.
>
> The first patch changes extlinux_read_bootflow() to use proper buffer
> alignment for DMA.
>
> The second patch changes the default alignment of fs_read_alloc() to be
> DMA-suitable, to fix other potential bugs.
>
> Nam Cao (2):
>   boot: extlinux: Fix unaligned buffer for reading data from file system
>   fs: Use ARCH_DMA_MINALIGN as default alignment for fs_read_alloc()
>
>  boot/bootmeth_extlinux.c | 3 ++-
>  fs/fs.c                  | 4 ++++
>  include/fs.h             | 2 +-
>  3 files changed, 7 insertions(+), 2 deletions(-)
>
> --
> 2.39.5
>

FYI, this "CACHE: Misaligned operation" problem was also fixed in
bootstd script method by this previous patch:
https://lists.denx.de/pipermail/u-boot/2023-September/530927.html

For the series.
Reviewed-by: Tony Dinh <mibodhi@gmail.com>

All the best,
Tony