Add a facility to globally override a feature, no matter what the HW says. Yes, this is dangerous.
Nothing uses this yet, so we are pretty safe. For now. Signed-off-by: Marc Zyngier <[email protected]> --- arch/arm64/include/asm/cpufeature.h | 2 ++ arch/arm64/kernel/cpufeature.c | 26 +++++++++++++++++++++----- 2 files changed, 23 insertions(+), 5 deletions(-) diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 9a555809b89c..465d2cb63bfc 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -75,6 +75,8 @@ struct arm64_ftr_reg { u64 sys_val; u64 user_val; const struct arm64_ftr_bits *ftr_bits; + u64 *override_val; + u64 *override_mask; }; extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0; diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index e99eddec0a46..492321054bd5 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -544,13 +544,17 @@ static const struct arm64_ftr_bits ftr_raz[] = { ARM64_FTR_END, }; -#define ARM64_FTR_REG(id, table) { \ - .sys_id = id, \ - .reg = &(struct arm64_ftr_reg){ \ - .name = #id, \ - .ftr_bits = &((table)[0]), \ +#define ARM64_FTR_REG_OVERRIDE(id, table, v, m) { \ + .sys_id = id, \ + .reg = &(struct arm64_ftr_reg){ \ + .name = #id, \ + .ftr_bits = &((table)[0]), \ + .override_val = v, \ + .override_mask = m, \ }} +#define ARM64_FTR_REG(id, table) ARM64_FTR_REG_OVERRIDE(id, table, NULL, NULL) + static const struct __ftr_reg_entry { u32 sys_id; struct arm64_ftr_reg *reg; @@ -786,6 +790,18 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new) val &= valid_mask; + if (reg->override_mask && reg->override_val) { + u64 override = val; + override &= ~*reg->override_mask; + override |= (*reg->override_val & *reg->override_mask); + + if (val != override) + pr_warn("%s: forced from %016llx to %016llx\n", + reg->name, val, override); + + val = override; + } + reg->sys_val = val; reg->strict_mask = strict_mask; reg->user_mask = user_mask; -- 2.29.2
