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arm64: cpuinfo: remove I-cache VIPT aliasing detection 

The CCSIDR_EL1.{NumSets,Associativity,LineSize} fields are only for use
in conjunction with set/way cache maintenance and are not guaranteed to
represent the actual microarchitectural features of a design.

The architecture explicitly states:

| You cannot make any inference about the actual sizes of caches based
| on these parameters.

We currently use these fields to determine whether or the I-cache is
aliasing, which is bogus and known to break on some platforms. Instead,
assume the I-cache is always aliasing if it advertises a VIPT policy.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Will Deacon 2017-03-10 20:32:20 +00:00 committed by Catalin Marinas
parent 97da3854c5
commit 3689c75af2
2 changed files with 10 additions and 26 deletions
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13
arch/arm64/include/asm/cachetype.h
View File

@ -63,19 +63,6 @@ extern unsigned long __icache_flags;
#define CACHE_NUMSETS(x) (CCSIDR_EL1_NUMSETS(x) + 1)
#define CACHE_ASSOCIATIVITY(x) (CCSIDR_EL1_ASSOCIATIVITY(x) + 1)
extern u64 __attribute_const__ cache_get_ccsidr(u64 csselr);
/* Helpers for Level 1 Instruction cache csselr = 1L */
static inline int icache_get_linesize(void)
{
return CACHE_LINESIZE(cache_get_ccsidr(1L));
}
static inline int icache_get_numsets(void)
{
return CACHE_NUMSETS(cache_get_ccsidr(1L));
}
/*
* Whilst the D-side always behaves as PIPT on AArch64, aliasing is
* permitted in the I-cache.

21
arch/arm64/kernel/cpuinfo.c
View File

@ -289,20 +289,17 @@ static void cpuinfo_detect_icache_policy(struct cpuinfo_arm64 *info)
unsigned int cpu = smp_processor_id();
u32 l1ip = CTR_L1IP(info->reg_ctr);
if (l1ip != ICACHE_POLICY_PIPT) {
/*
* VIPT caches are non-aliasing if the VA always equals the PA
* in all bit positions that are covered by the index. This is
* the case if the size of a way (# of sets * line size) does
* not exceed PAGE_SIZE.
*/
u32 waysize = icache_get_numsets() * icache_get_linesize();
if (l1ip != ICACHE_POLICY_VIPT || waysize > PAGE_SIZE)
switch (l1ip) {
case ICACHE_POLICY_PIPT:
break;
default:
case ICACHE_POLICY_AIVIVT:
set_bit(ICACHEF_AIVIVT, &__icache_flags);
/* Fallthrough */
case ICACHE_POLICY_VIPT:
/* Assume aliasing */
set_bit(ICACHEF_ALIASING, &__icache_flags);
}
if (l1ip == ICACHE_POLICY_AIVIVT)
set_bit(ICACHEF_AIVIVT, &__icache_flags);
pr_info("Detected %s I-cache on CPU%d\n", icache_policy_str[l1ip], cpu);
}