1 files changed, 146 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/feat_ctl.c b/arch/x86/kernel/cpu/feat_ctl.c
new file mode 100644
index 000000000..d75418512
--- /dev/null
+++ b/arch/x86/kernel/cpu/feat_ctl.c
@@ -0,0 +1,146 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/tboot.h>
+
+#include <asm/cpu.h>
+#include <asm/cpufeature.h>
+#include <asm/msr-index.h>
+#include <asm/processor.h>
+#include <asm/vmx.h>
+
+#undef pr_fmt
+#define pr_fmt(fmt)	"x86/cpu: " fmt
+
+#ifdef CONFIG_X86_VMX_FEATURE_NAMES
+enum vmx_feature_leafs {
+	MISC_FEATURES = 0,
+	PRIMARY_CTLS,
+	SECONDARY_CTLS,
+	NR_VMX_FEATURE_WORDS,
+};
+
+#define VMX_F(x) BIT(VMX_FEATURE_##x & 0x1f)
+
+static void init_vmx_capabilities(struct cpuinfo_x86 *c)
+{
+	u32 supported, funcs, ept, vpid, ign;
+
+	BUILD_BUG_ON(NVMXINTS != NR_VMX_FEATURE_WORDS);
+
+	/*
+	 * The high bits contain the allowed-1 settings, i.e. features that can
+	 * be turned on.  The low bits contain the allowed-0 settings, i.e.
+	 * features that can be turned off.  Ignore the allowed-0 settings,
+	 * if a feature can be turned on then it's supported.
+	 *
+	 * Use raw rdmsr() for primary processor controls and pin controls MSRs
+	 * as they exist on any CPU that supports VMX, i.e. we want the WARN if
+	 * the RDMSR faults.
+	 */
+	rdmsr(MSR_IA32_VMX_PROCBASED_CTLS, ign, supported);
+	c->vmx_capability[PRIMARY_CTLS] = supported;
+
+	rdmsr_safe(MSR_IA32_VMX_PROCBASED_CTLS2, &ign, &supported);
+	c->vmx_capability[SECONDARY_CTLS] = supported;
+
+	rdmsr(MSR_IA32_VMX_PINBASED_CTLS, ign, supported);
+	rdmsr_safe(MSR_IA32_VMX_VMFUNC, &ign, &funcs);
+
+	/*
+	 * Except for EPT+VPID, which enumerates support for both in a single
+	 * MSR, low for EPT, high for VPID.
+	 */
+	rdmsr_safe(MSR_IA32_VMX_EPT_VPID_CAP, &ept, &vpid);
+
+	/* Pin, EPT, VPID and VM-Func are merged into a single word. */
+	WARN_ON_ONCE(supported >> 16);
+	WARN_ON_ONCE(funcs >> 4);
+	c->vmx_capability[MISC_FEATURES] = (supported & 0xffff) |
+					   ((vpid & 0x1) << 16) |
+					   ((funcs & 0xf) << 28);
+
+	/* EPT bits are full on scattered and must be manually handled. */
+	if (ept & VMX_EPT_EXECUTE_ONLY_BIT)
+		c->vmx_capability[MISC_FEATURES] |= VMX_F(EPT_EXECUTE_ONLY);
+	if (ept & VMX_EPT_AD_BIT)
+		c->vmx_capability[MISC_FEATURES] |= VMX_F(EPT_AD);
+	if (ept & VMX_EPT_1GB_PAGE_BIT)
+		c->vmx_capability[MISC_FEATURES] |= VMX_F(EPT_1GB);
+
+	/* Synthetic APIC features that are aggregates of multiple features. */
+	if ((c->vmx_capability[PRIMARY_CTLS] & VMX_F(VIRTUAL_TPR)) &&
+	    (c->vmx_capability[SECONDARY_CTLS] & VMX_F(VIRT_APIC_ACCESSES)))
+		c->vmx_capability[MISC_FEATURES] |= VMX_F(FLEXPRIORITY);
+
+	if ((c->vmx_capability[PRIMARY_CTLS] & VMX_F(VIRTUAL_TPR)) &&
+	    (c->vmx_capability[SECONDARY_CTLS] & VMX_F(APIC_REGISTER_VIRT)) &&
+	    (c->vmx_capability[SECONDARY_CTLS] & VMX_F(VIRT_INTR_DELIVERY)) &&
+	    (c->vmx_capability[MISC_FEATURES] & VMX_F(POSTED_INTR)))
+		c->vmx_capability[MISC_FEATURES] |= VMX_F(APICV);
+
+	/* Set the synthetic cpufeatures to preserve /proc/cpuinfo's ABI. */
+	if (c->vmx_capability[PRIMARY_CTLS] & VMX_F(VIRTUAL_TPR))
+		set_cpu_cap(c, X86_FEATURE_TPR_SHADOW);
+	if (c->vmx_capability[MISC_FEATURES] & VMX_F(FLEXPRIORITY))
+		set_cpu_cap(c, X86_FEATURE_FLEXPRIORITY);
+	if (c->vmx_capability[MISC_FEATURES] & VMX_F(VIRTUAL_NMIS))
+		set_cpu_cap(c, X86_FEATURE_VNMI);
+	if (c->vmx_capability[SECONDARY_CTLS] & VMX_F(EPT))
+		set_cpu_cap(c, X86_FEATURE_EPT);
+	if (c->vmx_capability[MISC_FEATURES] & VMX_F(EPT_AD))
+		set_cpu_cap(c, X86_FEATURE_EPT_AD);
+	if (c->vmx_capability[MISC_FEATURES] & VMX_F(VPID))
+		set_cpu_cap(c, X86_FEATURE_VPID);
+}
+#endif /* CONFIG_X86_VMX_FEATURE_NAMES */
+
+void init_ia32_feat_ctl(struct cpuinfo_x86 *c)
+{
+	bool tboot = tboot_enabled();
+	u64 msr;
+
+	if (rdmsrl_safe(MSR_IA32_FEAT_CTL, &msr)) {
+		clear_cpu_cap(c, X86_FEATURE_VMX);
+		return;
+	}
+
+	if (msr & FEAT_CTL_LOCKED)
+		goto update_caps;
+
+	/*
+	 * Ignore whatever value BIOS left in the MSR to avoid enabling random
+	 * features or faulting on the WRMSR.
+	 */
+	msr = FEAT_CTL_LOCKED;
+
+	/*
+	 * Enable VMX if and only if the kernel may do VMXON at some point,
+	 * i.e. KVM is enabled, to avoid unnecessarily adding an attack vector
+	 * for the kernel, e.g. using VMX to hide malicious code.
+	 */
+	if (cpu_has(c, X86_FEATURE_VMX) && IS_ENABLED(CONFIG_KVM_INTEL)) {
+		msr |= FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX;
+
+		if (tboot)
+			msr |= FEAT_CTL_VMX_ENABLED_INSIDE_SMX;
+	}
+
+	wrmsrl(MSR_IA32_FEAT_CTL, msr);
+
+update_caps:
+	set_cpu_cap(c, X86_FEATURE_MSR_IA32_FEAT_CTL);
+
+	if (!cpu_has(c, X86_FEATURE_VMX))
+		return;
+
+	if ( (tboot && !(msr & FEAT_CTL_VMX_ENABLED_INSIDE_SMX)) ||
+	    (!tboot && !(msr & FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX))) {
+		if (IS_ENABLED(CONFIG_KVM_INTEL))
+			pr_err_once("VMX (%s TXT) disabled by BIOS\n",
+				    tboot ? "inside" : "outside");
+		clear_cpu_cap(c, X86_FEATURE_VMX);
+	} else {
+#ifdef CONFIG_X86_VMX_FEATURE_NAMES
+		init_vmx_capabilities(c);
+#endif
+	}
+}