[PATCH v5 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>
Acked-by: Julien Grall <jgrall@xxxxxxxxxx>
---
 xen/arch/arm/setup.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 7968cee47d..f16b33fa87 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_fp && (boot_cpu_feature64(fp) >= 2) )
+        printk(XENLOG_WARNING "WARNING: Unknown Floating-point ID:%d, "
+               "this may result in corruption on the platform\n",
+               boot_cpu_feature64(fp));
+
+    /* Warn user if we find unknown AdvancedSIMD features */
+    if ( cpu_has_simd && (boot_cpu_feature64(simd) >= 2) )
+        printk(XENLOG_WARNING "WARNING: Unknown AdvancedSIMD ID:%d, "
+               "this may result in 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",
-- 
2.17.1