[BUG] [openEuler-1.0-LTS] "CPU features: enabling workaround for Mismatched cache type" - Kernel

30 Aug 2022


      I've seen the following kernel log when booting openEuler-1.0-LTS
on my kunpeng-920:
"CPU features: enabling workaround for Mismatched cache type"
whilst all the CPUs in the system actually expose the *same* CTR_EL0
values, i.e., 0x0000000084448004.  The following piece of code looks
quite broken because ...
|static bool
|has_mismatched_cache_type(const struct arm64_cpu_capabilities *entry,
|			   int scope)
|{
|	u64 mask = arm64_ftr_reg_ctrel0.strict_mask;
|
|	/* Skip matching the min line sizes for cache type check */
|	if (entry->capability == ARM64_MISMATCHED_CACHE_TYPE)
|		mask ^= arm64_ftr_reg_ctrel0.strict_mask;
... 'mask' is always set to 0 during the detection of "Mismatched cache
type" but we actually want to check the whole *strict_mask*.
If I understand it correctly, backporting upstream commit 880f7cc47265
("arm64: cpu_errata: Remove ARM64_MISMATCHED_CACHE_LINE_SIZE") is the
right thing to do here.  But please have a look.
Zenghui