[PATCH 0/2] Correct the cache line size warning

Masayoshi Mizuma
2019-06-11T15:19:48Z

From: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>

If the cache line size is greater than ARCH_DMA_MINALIGN (128),
the warning shows and it's tainted as TAINT_CPU_OUT_OF_SPEC.

However, it's not good about two points.
First, as discussed in the thread [1], the cpu cache line size will be
problem only on non-coherent devices.
Then, it should not be tainted as TAINT_CPU_OUT_OF_SPEC because
according to the specification of CTR_EL0.CWG, the maximum cache
writeback granule is 2048 byte (CWG == 0b1001).

This patch series try to:

- Show the warning only if the device is non-coherent device and
ARCH_DMA_MINALIGN is smaller than the cpu cache size.

- Show the warning and taints as TAINT_CPU_OUT_OF_SPEC if the cache line
size is greater than the maximum.

[1] https://lore.kernel.org/linux-arm-kernel/20180514145703.celnlobzn3uh5tc2@localhost/

Masayoshi Mizuma (2):
arm64/mm: check cpu cache line size with non-coherent device
arm64/mm: show TAINT_CPU_OUT_OF_SPEC warning if the cache size is over
the spec.

arch/arm64/include/asm/cache.h | 2 ++
arch/arm64/mm/dma-mapping.c | 9 +++++----
arch/arm64/mm/init.c | 5 +++++
3 files changed, 12 insertions(+), 4 deletions(-)

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2.20.1