There is no way to proceed when requested register could not be searched in arm64_ftr_reg[]. Requesting for a non present register would be an error as well. Hence lets just WARN_ON() when search fails in get_arm64_ftr_reg() rather than checking for return value and doing a BUG_ON() instead in some individual callers. But there are also caller instances that dont error out when register search fails. Add a new helper get_arm64_ftr_reg_nowarn() for such cases.
Cc: Catalin Marinas <catalin.mari...@arm.com> Cc: Will Deacon <w...@kernel.org> Cc: Suzuki K Poulose <suzuki.poul...@arm.com> Cc: Mark Brown <broo...@kernel.org> Cc: linux-arm-ker...@lists.infradead.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Anshuman Khandual <anshuman.khand...@arm.com> --- Changes in V3: - Early return on register search failure in some callers per Will - Return 0, when search fails in check_update_ftr_reg() per Will Changes in V2: (https://patchwork.kernel.org/patch/11570575/) - Added get_arm64_ftr_reg_nowarn() per Will - read_sanitised_ftr_reg() returns 0 when register search fails per Catalin Changes in V1: (https://patchwork.kernel.org/patch/11559083/) arch/arm64/kernel/cpufeature.c | 45 ++++++++++++++++++++++++++-------- 1 file changed, 35 insertions(+), 10 deletions(-) diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index e744f647cbac..64e87a7b3c3c 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -597,16 +597,16 @@ static int search_cmp_ftr_reg(const void *id, const void *regp) } /* - * get_arm64_ftr_reg - Lookup a feature register entry using its - * sys_reg() encoding. With the array arm64_ftr_regs sorted in the - * ascending order of sys_id , we use binary search to find a matching + * get_arm64_ftr_reg_nowarn - Looks up a feature register entry using + * its sys_reg() encoding. With the array arm64_ftr_regs sorted in the + * ascending order of sys_id, we use binary search to find a matching * entry. * * returns - Upon success, matching ftr_reg entry for id. * - NULL on failure. It is upto the caller to decide * the impact of a failure. */ -static struct arm64_ftr_reg *get_arm64_ftr_reg(u32 sys_id) +static struct arm64_ftr_reg *get_arm64_ftr_reg_nowarn(u32 sys_id) { const struct __ftr_reg_entry *ret; @@ -620,6 +620,28 @@ static struct arm64_ftr_reg *get_arm64_ftr_reg(u32 sys_id) return NULL; } +/* + * get_arm64_ftr_reg - Looks up a feature register entry using + * its sys_reg() encoding. This calls get_arm64_ftr_reg_nowarn(). + * + * returns - Upon success, matching ftr_reg entry for id. + * - NULL on failure but with an WARN_ON(). + */ +static struct arm64_ftr_reg *get_arm64_ftr_reg(u32 sys_id) +{ + struct arm64_ftr_reg *reg; + + reg = get_arm64_ftr_reg_nowarn(sys_id); + + /* + * Can not really proceed when the search fails here. + * Requesting for a non existent register search will + * be an error. Warn but let it continue for now. + */ + WARN_ON(!reg); + return reg; +} + static u64 arm64_ftr_set_value(const struct arm64_ftr_bits *ftrp, s64 reg, s64 ftr_val) { @@ -681,7 +703,8 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new) const struct arm64_ftr_bits *ftrp; struct arm64_ftr_reg *reg = get_arm64_ftr_reg(sys_reg); - BUG_ON(!reg); + if (!reg) + return; for (ftrp = reg->ftr_bits; ftrp->width; ftrp++) { u64 ftr_mask = arm64_ftr_mask(ftrp); @@ -815,7 +838,9 @@ static int check_update_ftr_reg(u32 sys_id, int cpu, u64 val, u64 boot) { struct arm64_ftr_reg *regp = get_arm64_ftr_reg(sys_id); - BUG_ON(!regp); + if (!regp) + return 0; + update_cpu_ftr_reg(regp, val); if ((boot & regp->strict_mask) == (val & regp->strict_mask)) return 0; @@ -829,7 +854,7 @@ static void relax_cpu_ftr_reg(u32 sys_id, int field) const struct arm64_ftr_bits *ftrp; struct arm64_ftr_reg *regp = get_arm64_ftr_reg(sys_id); - if (WARN_ON(!regp)) + if (!regp) return; for (ftrp = regp->ftr_bits; ftrp->width; ftrp++) { @@ -1022,8 +1047,8 @@ u64 read_sanitised_ftr_reg(u32 id) { struct arm64_ftr_reg *regp = get_arm64_ftr_reg(id); - /* We shouldn't get a request for an unsupported register */ - BUG_ON(!regp); + if (!regp) + return 0; return regp->sys_val; } @@ -2663,7 +2688,7 @@ static int emulate_sys_reg(u32 id, u64 *valp) if (sys_reg_CRm(id) == 0) return emulate_id_reg(id, valp); - regp = get_arm64_ftr_reg(id); + regp = get_arm64_ftr_reg_nowarn(id); if (regp) *valp = arm64_ftr_reg_user_value(regp); else -- 2.20.1
