Commit 639475d4 authored by Marcos Del Sol Vives's avatar Marcos Del Sol Vives Committed by Borislav Petkov
Browse files

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: default avatarMarcos Del Sol Vives <marcos@orca.pet>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211017094408.1512158-1-marcos@orca.pet
parent f3f07ae4

arch/x86/Kconfig.cpu

+13 −0
Original line number Diff line number Diff line
@@ -508,3 +508,16 @@ config CPU_SUP_ZHAOXIN 
	  CPU might render the kernel unbootable.



	  If unsure, say N.



config CPU_SUP_VORTEX_32

	default y

	bool "Support Vortex processors" if PROCESSOR_SELECT

	depends on X86_32

	help

	  This enables detection, tunings and quirks for Vortex processors



	  You need this enabled if you want your kernel to run on a

	  Vortex CPU. Disabling this option on other types of CPUs

	  makes the kernel a tiny bit smaller.



	  If unsure, say N.

arch/x86/include/asm/processor.h

+2 −1
Original line number Diff line number Diff line
@@ -164,7 +164,8 @@ enum cpuid_regs_idx { 
#define X86_VENDOR_NSC		8

#define X86_VENDOR_HYGON	9

#define X86_VENDOR_ZHAOXIN	10

#define X86_VENDOR_NUM		11

#define X86_VENDOR_VORTEX	11

#define X86_VENDOR_NUM		12



#define X86_VENDOR_UNKNOWN	0xff

arch/x86/kernel/cpu/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ obj-$(CONFIG_CPU_SUP_CENTAUR) += centaur.o 
obj-$(CONFIG_CPU_SUP_TRANSMETA_32)	+= transmeta.o

obj-$(CONFIG_CPU_SUP_UMC_32)		+= umc.o

obj-$(CONFIG_CPU_SUP_ZHAOXIN)		+= zhaoxin.o

obj-$(CONFIG_CPU_SUP_VORTEX_32)		+= vortex.o



obj-$(CONFIG_X86_MCE)			+= mce/

obj-$(CONFIG_MTRR)			+= mtrr/

arch/x86/kernel/cpu/common.c

+2 −0
Original line number Diff line number Diff line
@@ -1044,6 +1044,8 @@ static const __initconst struct x86_cpu_id cpu_vuln_whitelist[] = { 
	VULNWL(CENTAUR,	5, X86_MODEL_ANY,	NO_SPECULATION),

	VULNWL(INTEL,	5, X86_MODEL_ANY,	NO_SPECULATION),

	VULNWL(NSC,	5, X86_MODEL_ANY,	NO_SPECULATION),

	VULNWL(VORTEX,	5, X86_MODEL_ANY,	NO_SPECULATION),

	VULNWL(VORTEX,	6, X86_MODEL_ANY,	NO_SPECULATION),



	/* Intel Family 6 */

	VULNWL_INTEL(ATOM_SALTWELL,		NO_SPECULATION | NO_ITLB_MULTIHIT),

arch/x86/kernel/cpu/vortex.c

0 → 100644
+39 −0
Original line number Diff line number Diff line 
// 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);