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

diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
index 814fe0d349b01d80ab3b80f69b00026098beb22b..eefc434351dba3a859f95f4a2c5785b8db50170d 100644 (file)
--- a/arch/x86/Kconfig.cpu
+++ b/arch/x86/Kconfig.cpu
@@ -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.

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 9ad2acaaae9b84be5bece5730bfb8e7c746cc892..64e5290b29d0eaa5f5e95fac34c21ffa227ca814 100644 (file)
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -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
 

diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
index 637b499450d10b4ee8800bd55826923884a2f05a..9661e3e802be56e937f137e467b7d4a1669d4410 100644 (file)
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -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/

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 0f8885949e8c4b602fefc2eaf918d11a2957c051..325d6022599b24536332b1651ab4d824bf8770e3 100644 (file)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -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),

diff --git a/arch/x86/kernel/cpu/vortex.c b/arch/x86/kernel/cpu/vortex.c
new file mode 100644 (file)
index 0000000..e268547
--- /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);