[MODERATED] [patch 1/8] [PATCH v1.3.1 1/7] Linux Patch 1

[konrad.wilk@oracle.com]

It does not do much except show the words 'Vulnerable'.

It assumes that Cyrix, Old Intel CPUs are immune to this.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
v3: Remove AMD
    s/md/mdd/
---
 arch/x86/include/asm/cpufeatures.h |  1 +
 arch/x86/kernel/cpu/bugs.c         |  8 ++++++++
 arch/x86/kernel/cpu/common.c       | 17 +++++++++++++++++
 drivers/base/cpu.c                 |  8 ++++++++
 include/linux/cpu.h                |  2 ++
 5 files changed, 36 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index d554c11e01ff..4393c10fcc6f 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -362,5 +362,6 @@
 #define X86_BUG_CPU_MELTDOWN		X86_BUG(14) /* CPU is affected by meltdown attack and needs kernel page table isolation */
 #define X86_BUG_SPECTRE_V1		X86_BUG(15) /* CPU is affected by Spectre variant 1 attack with conditional branches */
 #define X86_BUG_SPECTRE_V2		X86_BUG(16) /* CPU is affected by Spectre variant 2 attack with indirect branches */
+#define X86_BUG_CPU_MD			X86_BUG(17) /* CPU is affected by memory disambiguation. */
 
 #endif /* _ASM_X86_CPUFEATURES_H */
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index bfca937bdcc3..79dfc80c4b9c 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -340,4 +340,12 @@ ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, c
 		       boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? ", IBRS_FW" : "",
 		       spectre_v2_module_string());
 }
+
+ssize_t cpu_show_md(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	if (!boot_cpu_has_bug(X86_BUG_CPU_MD))
+		return sprintf(buf, "Not affected\n");
+
+	return sprintf(buf, "Vulnerable\n");
+}
 #endif
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 348cf4821240..4cd1c95e21b2 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -935,6 +935,21 @@ static bool __init cpu_vulnerable_to_meltdown(struct cpuinfo_x86 *c)
 	return true;
 }
 
+static const __initconst struct x86_cpu_id cpu_no_md[] = {
+	{ X86_VENDOR_CENTAUR,	5 },
+	{ X86_VENDOR_INTEL,	5 },
+	{ X86_VENDOR_NSC,	5 },
+	{ X86_VENDOR_ANY,	4 },
+	{}
+};
+
+static bool __init cpu_vulnerable_to_md(struct cpuinfo_x86 *c)
+{
+	if (x86_match_cpu(cpu_no_md))
+		return false;
+
+	return true;
+}
 /*
  * Do minimum CPU detection early.
  * Fields really needed: vendor, cpuid_level, family, model, mask,
@@ -988,6 +1003,8 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 		setup_force_cpu_bug(X86_BUG_SPECTRE_V1);
 		setup_force_cpu_bug(X86_BUG_SPECTRE_V2);
 	}
+	if (cpu_vulnerable_to_md(c))
+		setup_force_cpu_bug(X86_BUG_CPU_MD);
 
 	fpu__init_system(c);
 
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index d21a2d913107..bce01c4674c4 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -532,14 +532,22 @@ ssize_t __weak cpu_show_spectre_v2(struct device *dev,
 	return sprintf(buf, "Not affected\n");
 }
 
+ssize_t __weak cpu_show_md(struct device *dev,
+			   struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "Not affected\n");
+}
+
 static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL);
 static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL);
 static DEVICE_ATTR(spectre_v2, 0444, cpu_show_spectre_v2, NULL);
+static DEVICE_ATTR(md, 0444, cpu_show_md, NULL);
 
 static struct attribute *cpu_root_vulnerabilities_attrs[] = {
 	&dev_attr_meltdown.attr,
 	&dev_attr_spectre_v1.attr,
 	&dev_attr_spectre_v2.attr,
+	&dev_attr_md.attr,
 	NULL
 };
 
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 7b01bc11c692..3ca9de5d401a 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -53,6 +53,8 @@ extern ssize_t cpu_show_spectre_v1(struct device *dev,
 				   struct device_attribute *attr, char *buf);
 extern ssize_t cpu_show_spectre_v2(struct device *dev,
 				   struct device_attribute *attr, char *buf);
+extern ssize_t cpu_show_md(struct device *dev,
+			   struct device_attribute *attr, char *buf);
 
 extern __printf(4, 5)
 struct device *cpu_device_create(struct device *parent, void *drvdata,
-- 
2.14.3