arm64: errata: Hide CTR_EL0.DIC on systems affected by Neoverse-N1 #1542419

Cores affected by Neoverse-N1 #1542419 could execute a stale instruction
when a branch is updated to point to freshly generated instructions.

To workaround this issue we need user-space to issue unnecessary
icache maintenance that we can trap. Start by hiding CTR_EL0.DIC.

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
James Morse 2019-10-17 18:42:58 +01:00 committed by Catalin Marinas
parent 4f5cafb5cb
commit 05460849c3
5 changed files with 54 additions and 2 deletions

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@ -88,6 +88,8 @@ stable kernels.
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Neoverse-N1 | #1349291 | N/A |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Neoverse-N1 | #1542419 | ARM64_ERRATUM_1542419 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | MMU-500 | #841119,826419 | N/A |
+----------------+-----------------+-----------------+-----------------------------+
+----------------+-----------------+-----------------+-----------------------------+

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@ -558,6 +558,22 @@ config ARM64_ERRATUM_1463225
If unsure, say Y.
config ARM64_ERRATUM_1542419
bool "Neoverse-N1: workaround mis-ordering of instruction fetches"
default y
help
This option adds a workaround for ARM Neoverse-N1 erratum
1542419.
Affected Neoverse-N1 cores could execute a stale instruction when
modified by another CPU. The workaround depends on a firmware
counterpart.
Workaround the issue by hiding the DIC feature from EL0. This
forces user-space to perform cache maintenance.
If unsure, say Y.
config CAVIUM_ERRATUM_22375
bool "Cavium erratum 22375, 24313"
default y

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@ -52,7 +52,8 @@
#define ARM64_HAS_IRQ_PRIO_MASKING 42
#define ARM64_HAS_DCPODP 43
#define ARM64_WORKAROUND_1463225 44
#define ARM64_WORKAROUND_1542419 45
#define ARM64_NCAPS 45
#define ARM64_NCAPS 46
#endif /* __ASM_CPUCAPS_H */

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@ -87,13 +87,21 @@ has_mismatched_cache_type(const struct arm64_cpu_capabilities *entry,
}
static void
cpu_enable_trap_ctr_access(const struct arm64_cpu_capabilities *__unused)
cpu_enable_trap_ctr_access(const struct arm64_cpu_capabilities *cap)
{
u64 mask = arm64_ftr_reg_ctrel0.strict_mask;
bool enable_uct_trap = false;
/* Trap CTR_EL0 access on this CPU, only if it has a mismatch */
if ((read_cpuid_cachetype() & mask) !=
(arm64_ftr_reg_ctrel0.sys_val & mask))
enable_uct_trap = true;
/* ... or if the system is affected by an erratum */
if (cap->capability == ARM64_WORKAROUND_1542419)
enable_uct_trap = true;
if (enable_uct_trap)
sysreg_clear_set(sctlr_el1, SCTLR_EL1_UCT, 0);
}
@ -623,6 +631,18 @@ check_branch_predictor(const struct arm64_cpu_capabilities *entry, int scope)
return (need_wa > 0);
}
static bool __maybe_unused
has_neoverse_n1_erratum_1542419(const struct arm64_cpu_capabilities *entry,
int scope)
{
u32 midr = read_cpuid_id();
bool has_dic = read_cpuid_cachetype() & BIT(CTR_DIC_SHIFT);
const struct midr_range range = MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N1);
WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible());
return is_midr_in_range(midr, &range) && has_dic;
}
#ifdef CONFIG_HARDEN_EL2_VECTORS
static const struct midr_range arm64_harden_el2_vectors[] = {
@ -851,6 +871,16 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
.matches = has_cortex_a76_erratum_1463225,
},
#endif
#ifdef CONFIG_ARM64_ERRATUM_1542419
{
/* we depend on the firmware portion for correctness */
.desc = "ARM erratum 1542419 (kernel portion)",
.capability = ARM64_WORKAROUND_1542419,
.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
.matches = has_neoverse_n1_erratum_1542419,
.cpu_enable = cpu_enable_trap_ctr_access,
},
#endif
{
}

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@ -470,6 +470,9 @@ static void ctr_read_handler(unsigned int esr, struct pt_regs *regs)
int rt = ESR_ELx_SYS64_ISS_RT(esr);
unsigned long val = arm64_ftr_reg_user_value(&arm64_ftr_reg_ctrel0);
if (cpus_have_const_cap(ARM64_WORKAROUND_1542419))
val &= ~BIT(CTR_DIC_SHIFT);
pt_regs_write_reg(regs, rt, val);
arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE);