From: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
After cpu identification concludes, do a sanity check by comparing the
final x86_capability bitmask with the pre-defined required feature bits.
Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
Acked-by: H. Peter Anvin (Intel) <hpa@zytor.com>
---
Changelog v6:
- Add Peter's acked-by tag.
- Rename patch subject to imperative form.
- Add a char buffer to the x86_cap_name() call.
arch/x86/kernel/cpu/common.c | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 44ae2f936395..f4d4a4c17106 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1988,6 +1988,37 @@ const char *x86_cap_name(unsigned int bit, char *buf)
return buf;
}
+/*
+ * As a sanity check compare the final x86_capability bitmask with the initial
+ * predefined required feature bits. In case of a mismatch emit a warning with
+ * the faulty bitmask value.
+ */
+static void verify_required_features(const struct cpuinfo_x86 *c)
+{
+ u32 missing[NCAPINTS] = REQUIRED_MASK_INITIALIZER;
+ char cap_buf[16];
+ u32 error = 0;
+ unsigned int i;
+
+ for (i = 0; i < NCAPINTS; i++) {
+ missing[i] &= ~c->x86_capability[i];
+ error |= missing[i];
+ }
+
+ if (!error)
+ return; /* All good */
+
+ /*
+ * At least one required feature is missing. Print a warning,
+ * and taint the kernel.
+ */
+ pr_warn("cpu %d: missing required feature(s):", c->cpu_index);
+ for_each_set_bit(i, (void *)missing, NCAPINTS << 5)
+ pr_cont(" %s", x86_cap_name(i, cap_buf));
+ pr_cont("\n");
+ add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK);
+}
+
/*
* This does the hard work of actually picking apart the CPU stuff...
*/
@@ -2117,6 +2148,8 @@ static void identify_cpu(struct cpuinfo_x86 *c)
mcheck_cpu_init(c);
numa_add_cpu(smp_processor_id());
+
+ verify_required_features(c);
}
/*
--
2.53.0