arm64: cpufeature: Fix feature comparison for CTR_EL0.{CWG,ERG}

If CTR_EL0.{CWG,ERG} are 0b0000 then they must be interpreted to have
their architecturally maximum values, which defeats the use of
FTR_HIGHER_SAFE when sanitising CPU ID registers on heterogeneous
machines.

Introduce FTR_HIGHER_OR_ZERO_SAFE so that these fields effectively
saturate at zero.

Fixes: 3c739b571084 ("arm64: Keep track of CPU feature registers")
Cc: <stable@vger.kernel.org> # 4.4.x-
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 407e2bf..c96ffa4 100644 (file)
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -35,9 +35,10 @@
  */
 
 enum ftr_type {
-       FTR_EXACT,      /* Use a predefined safe value */
-       FTR_LOWER_SAFE, /* Smaller value is safe */
-       FTR_HIGHER_SAFE,/* Bigger value is safe */
+       FTR_EXACT,                      /* Use a predefined safe value */
+       FTR_LOWER_SAFE,                 /* Smaller value is safe */
+       FTR_HIGHER_SAFE,                /* Bigger value is safe */
+       FTR_HIGHER_OR_ZERO_SAFE,        /* Bigger value is safe, but 0 is biggest */
 };
 
 #define FTR_STRICT     true    /* SANITY check strict matching required */

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index f29f36a..d19d14b 100644 (file)
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -225,8 +225,8 @@ static const struct arm64_ftr_bits ftr_ctr[] = {
        ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_EXACT, 31, 1, 1), /* RES1 */
        ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, CTR_DIC_SHIFT, 1, 1),
        ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, CTR_IDC_SHIFT, 1, 1),
-       ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_HIGHER_SAFE, CTR_CWG_SHIFT, 4, 0),
-       ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_HIGHER_SAFE, CTR_ERG_SHIFT, 4, 0),
+       ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_HIGHER_OR_ZERO_SAFE, CTR_CWG_SHIFT, 4, 0),
+       ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_HIGHER_OR_ZERO_SAFE, CTR_ERG_SHIFT, 4, 0),
        ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, CTR_DMINLINE_SHIFT, 4, 1),
        /*
         * Linux can handle differing I-cache policies. Userspace JITs will
@@ -468,6 +468,10 @@ static s64 arm64_ftr_safe_value(const struct arm64_ftr_bits *ftrp, s64 new,
        case FTR_LOWER_SAFE:
                ret = new < cur ? new : cur;
                break;
+       case FTR_HIGHER_OR_ZERO_SAFE:
+               if (!cur || !new)
+                       break;
+               /* Fallthrough */
        case FTR_HIGHER_SAFE:
                ret = new > cur ? new : cur;
                break;