arch/x86/kernel/cpu/feat_ctl.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/tboot.h>
   3
   4 #include <asm/cpufeature.h>
   5 #include <asm/msr-index.h>
   6 #include <asm/processor.h>
   7 #include <asm/vmx.h>
   8 #include "cpu.h"
   9
  10 #undef pr_fmt
  11 #define pr_fmt(fmt)     "x86/cpu: " fmt
  12
  13 #ifdef CONFIG_X86_VMX_FEATURE_NAMES
  14 enum vmx_feature_leafs {
  15         MISC_FEATURES = 0,
  16         PRIMARY_CTLS,
  17         SECONDARY_CTLS,
  18         NR_VMX_FEATURE_WORDS,
  19 };
  20
  21 #define VMX_F(x) BIT(VMX_FEATURE_##x & 0x1f)
  22
  23 static void init_vmx_capabilities(struct cpuinfo_x86 *c)
  24 {
  25         u32 supported, funcs, ept, vpid, ign;
  26
  27         BUILD_BUG_ON(NVMXINTS != NR_VMX_FEATURE_WORDS);
  28
  29         /*
  30          * The high bits contain the allowed-1 settings, i.e. features that can
  31          * be turned on.  The low bits contain the allowed-0 settings, i.e.
  32          * features that can be turned off.  Ignore the allowed-0 settings,
  33          * if a feature can be turned on then it's supported.
  34          *
  35          * Use raw rdmsr() for primary processor controls and pin controls MSRs
  36          * as they exist on any CPU that supports VMX, i.e. we want the WARN if
  37          * the RDMSR faults.
  38          */
  39         rdmsr(MSR_IA32_VMX_PROCBASED_CTLS, ign, supported);
  40         c->vmx_capability[PRIMARY_CTLS] = supported;
  41
  42         rdmsr_safe(MSR_IA32_VMX_PROCBASED_CTLS2, &ign, &supported);
  43         c->vmx_capability[SECONDARY_CTLS] = supported;
  44
  45         rdmsr(MSR_IA32_VMX_PINBASED_CTLS, ign, supported);
  46         rdmsr_safe(MSR_IA32_VMX_VMFUNC, &ign, &funcs);
  47
  48         /*
  49          * Except for EPT+VPID, which enumerates support for both in a single
  50          * MSR, low for EPT, high for VPID.
  51          */
  52         rdmsr_safe(MSR_IA32_VMX_EPT_VPID_CAP, &ept, &vpid);
  53
  54         /* Pin, EPT, VPID and VM-Func are merged into a single word. */
  55         WARN_ON_ONCE(supported >> 16);
  56         WARN_ON_ONCE(funcs >> 4);
  57         c->vmx_capability[MISC_FEATURES] = (supported & 0xffff) |
  58                                            ((vpid & 0x1) << 16) |
  59                                            ((funcs & 0xf) << 28);
  60
  61         /* EPT bits are full on scattered and must be manually handled. */
  62         if (ept & VMX_EPT_EXECUTE_ONLY_BIT)
  63                 c->vmx_capability[MISC_FEATURES] |= VMX_F(EPT_EXECUTE_ONLY);
  64         if (ept & VMX_EPT_AD_BIT)
  65                 c->vmx_capability[MISC_FEATURES] |= VMX_F(EPT_AD);
  66         if (ept & VMX_EPT_1GB_PAGE_BIT)
  67                 c->vmx_capability[MISC_FEATURES] |= VMX_F(EPT_1GB);
  68
  69         /* Synthetic APIC features that are aggregates of multiple features. */
  70         if ((c->vmx_capability[PRIMARY_CTLS] & VMX_F(VIRTUAL_TPR)) &&
  71             (c->vmx_capability[SECONDARY_CTLS] & VMX_F(VIRT_APIC_ACCESSES)))
  72                 c->vmx_capability[MISC_FEATURES] |= VMX_F(FLEXPRIORITY);
  73
  74         if ((c->vmx_capability[PRIMARY_CTLS] & VMX_F(VIRTUAL_TPR)) &&
  75             (c->vmx_capability[SECONDARY_CTLS] & VMX_F(APIC_REGISTER_VIRT)) &&
  76             (c->vmx_capability[SECONDARY_CTLS] & VMX_F(VIRT_INTR_DELIVERY)) &&
  77             (c->vmx_capability[MISC_FEATURES] & VMX_F(POSTED_INTR)))
  78                 c->vmx_capability[MISC_FEATURES] |= VMX_F(APICV);
  79
  80         /* Set the synthetic cpufeatures to preserve /proc/cpuinfo's ABI. */
  81         if (c->vmx_capability[PRIMARY_CTLS] & VMX_F(VIRTUAL_TPR))
  82                 set_cpu_cap(c, X86_FEATURE_TPR_SHADOW);
  83         if (c->vmx_capability[MISC_FEATURES] & VMX_F(FLEXPRIORITY))
  84                 set_cpu_cap(c, X86_FEATURE_FLEXPRIORITY);
  85         if (c->vmx_capability[MISC_FEATURES] & VMX_F(VIRTUAL_NMIS))
  86                 set_cpu_cap(c, X86_FEATURE_VNMI);
  87         if (c->vmx_capability[SECONDARY_CTLS] & VMX_F(EPT))
  88                 set_cpu_cap(c, X86_FEATURE_EPT);
  89         if (c->vmx_capability[MISC_FEATURES] & VMX_F(EPT_AD))
  90                 set_cpu_cap(c, X86_FEATURE_EPT_AD);
  91         if (c->vmx_capability[MISC_FEATURES] & VMX_F(VPID))
  92                 set_cpu_cap(c, X86_FEATURE_VPID);
  93 }
  94 #endif /* CONFIG_X86_VMX_FEATURE_NAMES */
  95
  96 static int __init nosgx(char *str)
  97 {
  98         setup_clear_cpu_cap(X86_FEATURE_SGX);
  99
 100         return 0;
 101 }
 102
 103 early_param("nosgx", nosgx);
 104
 105 void init_ia32_feat_ctl(struct cpuinfo_x86 *c)
 106 {
 107         bool enable_sgx_kvm = false, enable_sgx_driver = false;
 108         bool tboot = tboot_enabled();
 109         bool enable_vmx;
 110         u64 msr;
 111
 112         if (rdmsrl_safe(MSR_IA32_FEAT_CTL, &msr)) {
 113                 clear_cpu_cap(c, X86_FEATURE_VMX);
 114                 clear_cpu_cap(c, X86_FEATURE_SGX);
 115                 return;
 116         }
 117
 118         enable_vmx = cpu_has(c, X86_FEATURE_VMX) &&
 119                      IS_ENABLED(CONFIG_KVM_INTEL);
 120
 121         if (cpu_has(c, X86_FEATURE_SGX) && IS_ENABLED(CONFIG_X86_SGX)) {
 122                 /*
 123                  * Separate out SGX driver enabling from KVM.  This allows KVM
 124                  * guests to use SGX even if the kernel SGX driver refuses to
 125                  * use it.  This happens if flexible Launch Control is not
 126                  * available.
 127                  */
 128                 enable_sgx_driver = cpu_has(c, X86_FEATURE_SGX_LC);
 129                 enable_sgx_kvm = enable_vmx && IS_ENABLED(CONFIG_X86_SGX_KVM);
 130         }
 131
 132         if (msr & FEAT_CTL_LOCKED)
 133                 goto update_caps;
 134
 135         /*
 136          * Ignore whatever value BIOS left in the MSR to avoid enabling random
 137          * features or faulting on the WRMSR.
 138          */
 139         msr = FEAT_CTL_LOCKED;
 140
 141         /*
 142          * Enable VMX if and only if the kernel may do VMXON at some point,
 143          * i.e. KVM is enabled, to avoid unnecessarily adding an attack vector
 144          * for the kernel, e.g. using VMX to hide malicious code.
 145          */
 146         if (enable_vmx) {
 147                 msr |= FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX;
 148
 149                 if (tboot)
 150                         msr |= FEAT_CTL_VMX_ENABLED_INSIDE_SMX;
 151         }
 152
 153         if (enable_sgx_kvm || enable_sgx_driver) {
 154                 msr |= FEAT_CTL_SGX_ENABLED;
 155                 if (enable_sgx_driver)
 156                         msr |= FEAT_CTL_SGX_LC_ENABLED;
 157         }
 158
 159         wrmsrl(MSR_IA32_FEAT_CTL, msr);
 160
 161 update_caps:
 162         set_cpu_cap(c, X86_FEATURE_MSR_IA32_FEAT_CTL);
 163
 164         if (!cpu_has(c, X86_FEATURE_VMX))
 165                 goto update_sgx;
 166
 167         if ( (tboot && !(msr & FEAT_CTL_VMX_ENABLED_INSIDE_SMX)) ||
 168             (!tboot && !(msr & FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX))) {
 169                 if (IS_ENABLED(CONFIG_KVM_INTEL))
 170                         pr_err_once("VMX (%s TXT) disabled by BIOS\n",
 171                                     tboot ? "inside" : "outside");
 172                 clear_cpu_cap(c, X86_FEATURE_VMX);
 173         } else {
 174 #ifdef CONFIG_X86_VMX_FEATURE_NAMES
 175                 init_vmx_capabilities(c);
 176 #endif
 177         }
 178
 179 update_sgx:
 180         if (!(msr & FEAT_CTL_SGX_ENABLED)) {
 181                 if (enable_sgx_kvm || enable_sgx_driver)
 182                         pr_err_once("SGX disabled by BIOS.\n");
 183                 clear_cpu_cap(c, X86_FEATURE_SGX);
 184                 return;
 185         }
 186
 187         /*
 188          * VMX feature bit may be cleared due to being disabled in BIOS,
 189          * in which case SGX virtualization cannot be supported either.
 190          */
 191         if (!cpu_has(c, X86_FEATURE_VMX) && enable_sgx_kvm) {
 192                 pr_err_once("SGX virtualization disabled due to lack of VMX.\n");
 193                 enable_sgx_kvm = 0;
 194         }
 195
 196         if (!(msr & FEAT_CTL_SGX_LC_ENABLED) && enable_sgx_driver) {
 197                 if (!enable_sgx_kvm) {
 198                         pr_err_once("SGX Launch Control is locked. Disable SGX.\n");
 199                         clear_cpu_cap(c, X86_FEATURE_SGX);
 200                 } else {
 201                         pr_err_once("SGX Launch Control is locked. Support SGX virtualization only.\n");
 202                         clear_cpu_cap(c, X86_FEATURE_SGX_LC);
 203                 }
 204         }
 205 }