x86/kernel/cpu/feat_ctl.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/tboot.h>
   3
   4 #include <asm/cpu.h>
   5 #include <asm/cpufeature.h>
   6 #include <asm/msr-index.h>
   7 #include <asm/processor.h>
   8 #include <asm/vmx.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         TERTIARY_CTLS_LOW,
  19         TERTIARY_CTLS_HIGH,
  20         NR_VMX_FEATURE_WORDS,
  21 };
  22
  23 #define VMX_F(x) BIT(VMX_FEATURE_##x & 0x1f)
  24
  25 static void init_vmx_capabilities(struct cpuinfo_x86 *c)
  26 {
  27         u32 supported, funcs, ept, vpid, ign, low, high;
  28
  29         BUILD_BUG_ON(NVMXINTS != NR_VMX_FEATURE_WORDS);
  30
  31         /*
  32          * The high bits contain the allowed-1 settings, i.e. features that can
  33          * be turned on.  The low bits contain the allowed-0 settings, i.e.
  34          * features that can be turned off.  Ignore the allowed-0 settings,
  35          * if a feature can be turned on then it's supported.
  36          *
  37          * Use raw rdmsr() for primary processor controls and pin controls MSRs
  38          * as they exist on any CPU that supports VMX, i.e. we want the WARN if
  39          * the RDMSR faults.
  40          */
  41         rdmsr(MSR_IA32_VMX_PROCBASED_CTLS, ign, supported);
  42         c->vmx_capability[PRIMARY_CTLS] = supported;
  43
  44         rdmsr_safe(MSR_IA32_VMX_PROCBASED_CTLS2, &ign, &supported);
  45         c->vmx_capability[SECONDARY_CTLS] = supported;
  46
  47         /* All 64 bits of tertiary controls MSR are allowed-1 settings. */
  48         rdmsr_safe(MSR_IA32_VMX_PROCBASED_CTLS3, &low, &high);
  49         c->vmx_capability[TERTIARY_CTLS_LOW] = low;
  50         c->vmx_capability[TERTIARY_CTLS_HIGH] = high;
  51
  52         rdmsr(MSR_IA32_VMX_PINBASED_CTLS, ign, supported);
  53         rdmsr_safe(MSR_IA32_VMX_VMFUNC, &ign, &funcs);
  54
  55         /*
  56          * Except for EPT+VPID, which enumerates support for both in a single
  57          * MSR, low for EPT, high for VPID.
  58          */
  59         rdmsr_safe(MSR_IA32_VMX_EPT_VPID_CAP, &ept, &vpid);
  60
  61         /* Pin, EPT, VPID and VM-Func are merged into a single word. */
  62         WARN_ON_ONCE(supported >> 16);
  63         WARN_ON_ONCE(funcs >> 4);
  64         c->vmx_capability[MISC_FEATURES] = (supported & 0xffff) |
  65                                            ((vpid & 0x1) << 16) |
  66                                            ((funcs & 0xf) << 28);
  67
  68         /* EPT bits are full on scattered and must be manually handled. */
  69         if (ept & VMX_EPT_EXECUTE_ONLY_BIT)
  70                 c->vmx_capability[MISC_FEATURES] |= VMX_F(EPT_EXECUTE_ONLY);
  71         if (ept & VMX_EPT_AD_BIT)
  72                 c->vmx_capability[MISC_FEATURES] |= VMX_F(EPT_AD);
  73         if (ept & VMX_EPT_1GB_PAGE_BIT)
  74                 c->vmx_capability[MISC_FEATURES] |= VMX_F(EPT_1GB);
  75
  76         /* Synthetic APIC features that are aggregates of multiple features. */
  77         if ((c->vmx_capability[PRIMARY_CTLS] & VMX_F(VIRTUAL_TPR)) &&
  78             (c->vmx_capability[SECONDARY_CTLS] & VMX_F(VIRT_APIC_ACCESSES)))
  79                 c->vmx_capability[MISC_FEATURES] |= VMX_F(FLEXPRIORITY);
  80
  81         if ((c->vmx_capability[PRIMARY_CTLS] & VMX_F(VIRTUAL_TPR)) &&
  82             (c->vmx_capability[SECONDARY_CTLS] & VMX_F(APIC_REGISTER_VIRT)) &&
  83             (c->vmx_capability[SECONDARY_CTLS] & VMX_F(VIRT_INTR_DELIVERY)) &&
  84             (c->vmx_capability[MISC_FEATURES] & VMX_F(POSTED_INTR)))
  85                 c->vmx_capability[MISC_FEATURES] |= VMX_F(APICV);
  86
  87         /* Set the synthetic cpufeatures to preserve /proc/cpuinfo's ABI. */
  88         if (c->vmx_capability[PRIMARY_CTLS] & VMX_F(VIRTUAL_TPR))
  89                 set_cpu_cap(c, X86_FEATURE_TPR_SHADOW);
  90         if (c->vmx_capability[MISC_FEATURES] & VMX_F(FLEXPRIORITY))
  91                 set_cpu_cap(c, X86_FEATURE_FLEXPRIORITY);
  92         if (c->vmx_capability[MISC_FEATURES] & VMX_F(VIRTUAL_NMIS))
  93                 set_cpu_cap(c, X86_FEATURE_VNMI);
  94         if (c->vmx_capability[SECONDARY_CTLS] & VMX_F(EPT))
  95                 set_cpu_cap(c, X86_FEATURE_EPT);
  96         if (c->vmx_capability[MISC_FEATURES] & VMX_F(EPT_AD))
  97                 set_cpu_cap(c, X86_FEATURE_EPT_AD);
  98         if (c->vmx_capability[MISC_FEATURES] & VMX_F(VPID))
  99                 set_cpu_cap(c, X86_FEATURE_VPID);
 100 }
 101 #endif /* CONFIG_X86_VMX_FEATURE_NAMES */
 102
 103 static int __init nosgx(char *str)
 104 {
 105         setup_clear_cpu_cap(X86_FEATURE_SGX);
 106
 107         return 0;
 108 }
 109
 110 early_param("nosgx", nosgx);
 111
 112 void init_ia32_feat_ctl(struct cpuinfo_x86 *c)
 113 {
 114         bool enable_sgx_kvm = false, enable_sgx_driver = false;
 115         bool tboot = tboot_enabled();
 116         bool enable_vmx;
 117         u64 msr;
 118
 119         if (rdmsrl_safe(MSR_IA32_FEAT_CTL, &msr)) {
 120                 clear_cpu_cap(c, X86_FEATURE_VMX);
 121                 clear_cpu_cap(c, X86_FEATURE_SGX);
 122                 return;
 123         }
 124
 125         enable_vmx = cpu_has(c, X86_FEATURE_VMX) &&
 126                      IS_ENABLED(CONFIG_KVM_INTEL);
 127
 128         if (cpu_has(c, X86_FEATURE_SGX) && IS_ENABLED(CONFIG_X86_SGX)) {
 129                 /*
 130                  * Separate out SGX driver enabling from KVM.  This allows KVM
 131                  * guests to use SGX even if the kernel SGX driver refuses to
 132                  * use it.  This happens if flexible Launch Control is not
 133                  * available.
 134                  */
 135                 enable_sgx_driver = cpu_has(c, X86_FEATURE_SGX_LC);
 136                 enable_sgx_kvm = enable_vmx && IS_ENABLED(CONFIG_X86_SGX_KVM);
 137         }
 138
 139         if (msr & FEAT_CTL_LOCKED)
 140                 goto update_caps;
 141
 142         /*
 143          * Ignore whatever value BIOS left in the MSR to avoid enabling random
 144          * features or faulting on the WRMSR.
 145          */
 146         msr = FEAT_CTL_LOCKED;
 147
 148         /*
 149          * Enable VMX if and only if the kernel may do VMXON at some point,
 150          * i.e. KVM is enabled, to avoid unnecessarily adding an attack vector
 151          * for the kernel, e.g. using VMX to hide malicious code.
 152          */
 153         if (enable_vmx) {
 154                 msr |= FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX;
 155
 156                 if (tboot)
 157                         msr |= FEAT_CTL_VMX_ENABLED_INSIDE_SMX;
 158         }
 159
 160         if (enable_sgx_kvm || enable_sgx_driver) {
 161                 msr |= FEAT_CTL_SGX_ENABLED;
 162                 if (enable_sgx_driver)
 163                         msr |= FEAT_CTL_SGX_LC_ENABLED;
 164         }
 165
 166         wrmsrl(MSR_IA32_FEAT_CTL, msr);
 167
 168 update_caps:
 169         set_cpu_cap(c, X86_FEATURE_MSR_IA32_FEAT_CTL);
 170
 171         if (!cpu_has(c, X86_FEATURE_VMX))
 172                 goto update_sgx;
 173
 174         if ( (tboot && !(msr & FEAT_CTL_VMX_ENABLED_INSIDE_SMX)) ||
 175             (!tboot && !(msr & FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX))) {
 176                 if (IS_ENABLED(CONFIG_KVM_INTEL))
 177                         pr_err_once("VMX (%s TXT) disabled by BIOS\n",
 178                                     tboot ? "inside" : "outside");
 179                 clear_cpu_cap(c, X86_FEATURE_VMX);
 180         } else {
 181 #ifdef CONFIG_X86_VMX_FEATURE_NAMES
 182                 init_vmx_capabilities(c);
 183 #endif
 184         }
 185
 186 update_sgx:
 187         if (!(msr & FEAT_CTL_SGX_ENABLED)) {
 188                 if (enable_sgx_kvm || enable_sgx_driver)
 189                         pr_err_once("SGX disabled by BIOS.\n");
 190                 clear_cpu_cap(c, X86_FEATURE_SGX);
 191                 return;
 192         }
 193
 194         /*
 195          * VMX feature bit may be cleared due to being disabled in BIOS,
 196          * in which case SGX virtualization cannot be supported either.
 197          */
 198         if (!cpu_has(c, X86_FEATURE_VMX) && enable_sgx_kvm) {
 199                 pr_err_once("SGX virtualization disabled due to lack of VMX.\n");
 200                 enable_sgx_kvm = 0;
 201         }
 202
 203         if (!(msr & FEAT_CTL_SGX_LC_ENABLED) && enable_sgx_driver) {
 204                 if (!enable_sgx_kvm) {
 205                         pr_err_once("SGX Launch Control is locked. Disable SGX.\n");
 206                         clear_cpu_cap(c, X86_FEATURE_SGX);
 207                 } else {
 208                         pr_err_once("SGX Launch Control is locked. Support SGX virtualization only.\n");
 209                         clear_cpu_cap(c, X86_FEATURE_SGX_LC);
 210                 }
 211         }
 212 }