x86/CPU: Add support for Vortex CPUs

DM&P devices were not being properly identified, which resulted in
unneeded Spectre/Meltdown mitigations being applied.

The manufacturer states that these devices execute always in-order and
don't support either speculative execution or branch prediction, so
they are not vulnerable to this class of attack. [1]

This is something I've personally tested by a simple timing analysis
on my Vortex86MX CPU, and can confirm it is true.

Add identification for some devices that lack the CPUID product name
call, so they appear properly on /proc/cpuinfo.

¹https://www.ssv-embedded.de/doks/infos/DMP_Ann_180108_Meltdown.pdf

 [ bp: Massage commit message. ]

Signed-off-by: Marcos Del Sol Vives <marcos@orca.pet>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211017094408.1512158-1-marcos@orca.pet

1 files changed, 39 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/vortex.c b/arch/x86/kernel/cpu/vortex.c
new file mode 100644
index 000000000000..e2685470ba94
--- /dev/null
+++ b/arch/x86/kernel/cpu/vortex.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <asm/processor.h>
+#include "cpu.h"
+
+/*
+ * No special init required for Vortex processors.
+ */
+
+static const struct cpu_dev vortex_cpu_dev = {
+	.c_vendor	= "Vortex",
+	.c_ident	= { "Vortex86 SoC" },
+	.legacy_models	= {
+		{
+			.family = 5,
+			.model_names = {
+				[2] = "Vortex86DX",
+				[8] = "Vortex86MX",
+			},
+		},
+		{
+			.family = 6,
+			.model_names = {
+				/*
+				 * Both the Vortex86EX and the Vortex86EX2
+				 * have the same family and model id.
+				 *
+				 * However, the -EX2 supports the product name
+				 * CPUID call, so this name will only be used
+				 * for the -EX, which does not.
+				 */
+				[0] = "Vortex86EX",
+			},
+		},
+	},
+	.c_x86_vendor	= X86_VENDOR_VORTEX,
+};
+
+cpu_dev_register(vortex_cpu_dev);