arm64: cpufeature: Add helper to test for CPU feature overrides

[linux-2.6-microblaze.git] / arch / arm64 / include / asm / cpufeature.h

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 21c824e..acd8f49 100644 (file)
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -915,6 +915,45 @@ extern struct arm64_ftr_override id_aa64isar2_override;
 
 extern struct arm64_ftr_override arm64_sw_feature_override;
 
+static inline
+u64 arm64_apply_feature_override(u64 val, int feat, int width,
+                                const struct arm64_ftr_override *override)
+{
+       u64 oval = override->val;
+
+       /*
+        * When it encounters an invalid override (e.g., an override that
+        * cannot be honoured due to a missing CPU feature), the early idreg
+        * override code will set the mask to 0x0 and the value to non-zero for
+        * the field in question. In order to determine whether the override is
+        * valid or not for the field we are interested in, we first need to
+        * disregard bits belonging to other fields.
+        */
+       oval &= GENMASK_ULL(feat + width - 1, feat);
+
+       /*
+        * The override is valid if all value bits are accounted for in the
+        * mask. If so, replace the masked bits with the override value.
+        */
+       if (oval == (oval & override->mask)) {
+               val &= ~override->mask;
+               val |= oval;
+       }
+
+       /* Extract the field from the updated value */
+       return cpuid_feature_extract_unsigned_field(val, feat);
+}
+
+static inline bool arm64_test_sw_feature_override(int feat)
+{
+       /*
+        * Software features are pseudo CPU features that have no underlying
+        * CPUID system register value to apply the override to.
+        */
+       return arm64_apply_feature_override(0, feat, 4,
+                                           &arm64_sw_feature_override);
+}
+
 u32 get_kvm_ipa_limit(void);
 void dump_cpu_features(void);