[PATCH v3 2/2] xen/arm: Throw messages for unknown FP/SIMD implement ID

[Wei Chen <wei.chen@xxxxxxx>]

Arm ID_AA64PFR0_EL1 register provides two fields to describe CPU
FP/SIMD implementations. Currently, we exactly know the meaning of
0x0, 0x1 and 0xf of these fields. Xen treats value < 8 as FP/SIMD
features presented. If there is a value 0x2 bumped in the future,
Xen behaviors for value <= 0x1 can also take effect. But what Xen
done for value <= 0x1 may not always cover new value 0x2 required.
We throw these messages to break the silence when Xen detected
unknown FP/SIMD IDs to notice user to check.

Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
---
 xen/arch/arm/setup.c             | 12 ++++++++++++
 xen/include/asm-arm/cpufeature.h |  2 ++
 2 files changed, 14 insertions(+)

diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 7968cee47d..ef39ce1ec6 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -133,6 +133,18 @@ static void __init processor_id(void)
            cpu_has_simd ? " AdvancedSIMD" : "",
            cpu_has_gicv3 ? " GICv3-SysReg" : "");
 
+    /* Warn user if we find unknown floating-point features */
+    if ( cpu_has_unknown_fp )
+        printk(XENLOG_WARNING "WARNING: Unknown Floating-point ID:%d, "
+               "this may result to corruption on the platform\n",
+               boot_cpu_feature64(fp));
+
+    /* Warn user if we find unknown AdvancedSIMD features */
+    if ( cpu_has_unknown_simd )
+        printk(XENLOG_WARNING "WARNING: Unknown AdvancedSIMD ID:%d, "
+               "this may result to corruption on the platform\n",
+               boot_cpu_feature64(simd));
+
     printk("  Debug Features: %016"PRIx64" %016"PRIx64"\n",
            boot_cpu_data.dbg64.bits[0], boot_cpu_data.dbg64.bits[1]);
     printk("  Auxiliary Features: %016"PRIx64" %016"PRIx64"\n",
diff --git a/xen/include/asm-arm/cpufeature.h b/xen/include/asm-arm/cpufeature.h
index 10878ead8a..a32309986e 100644
--- a/xen/include/asm-arm/cpufeature.h
+++ b/xen/include/asm-arm/cpufeature.h
@@ -16,6 +16,8 @@
 #define cpu_has_fp        (boot_cpu_feature64(fp) < 8)
 #define cpu_has_simd      (boot_cpu_feature64(simd) < 8)
 #define cpu_has_gicv3     (boot_cpu_feature64(gic) == 1)
+#define cpu_has_unknown_fp   (cpu_has_fp && (boot_cpu_feature64(fp) >= 2))
+#define cpu_has_unknown_simd (cpu_has_simd && (boot_cpu_feature64(simd) >= 2))
 #endif
 
 #define cpu_feature32(c, feat)         ((c)->pfr32.feat)
-- 
2.17.1