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Commit 3689c75a authored by Will Deacon's avatar Will Deacon Committed by Catalin Marinas
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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: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 97da3854

arch/arm64/include/asm/cachetype.h

+0 −13
Original line number Diff line number Diff line
@@ -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.

arch/arm64/kernel/cpuinfo.c

+10 −13
Original line number Diff line number Diff line
@@ -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);

}