Re: [PATCH] KVM: x86/cpuid: Exclude unpermitted xfeatures sizes at KVM_GET_SUPPORTED_CPUID

From: kernel test robot
Date: Mon Jan 24 2022 - 23:48:30 EST

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In reply to: kernel test robot: "Re: [PATCH] KVM: x86/cpuid: Exclude unpermitted xfeatures sizes at KVM_GET_SUPPORTED_CPUID"
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Hi Like,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on kvm/queue]
[also build test ERROR on v5.17-rc1 next-20220124]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url: https://github.com/0day-ci/linux/commits/Like-Xu/KVM-x86-cpuid-Exclude-unpermitted-xfeatures-sizes-at-KVM_GET_SUPPORTED_CPUID/20220124-160452
base: https://git.kernel.org/pub/scm/virt/kvm/kvm.git queue
config: i386-randconfig-a002 (https://download.01.org/0day-ci/archive/20220125/202201251137.85eenHWr-lkp@xxxxxxxxx/config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 2e58a18910867ba6795066e044293e6daf89edf5)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/0day-ci/linux/commit/b29c71ea177d9a2225208d501987598610261749
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Like-Xu/KVM-x86-cpuid-Exclude-unpermitted-xfeatures-sizes-at-KVM_GET_SUPPORTED_CPUID/20220124-160452
git checkout b29c71ea177d9a2225208d501987598610261749
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 SHELL=/bin/bash

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>

All errors (new ones prefixed by >>):

>> arch/x86/kvm/cpuid.c:890:24: error: variable 'supported_xcr0' is uninitialized when used within its own initialization [-Werror,-Wuninitialized]
u64 supported_xcr0 = supported_xcr0 & xstate_get_guest_group_perm();
~~~~~~~~~~~~~~ ^~~~~~~~~~~~~~
1 error generated.

vim +/supported_xcr0 +890 arch/x86/kvm/cpuid.c

758
759 static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
760 {
761 struct kvm_cpuid_entry2 *entry;
762 int r, i, max_idx;
763
764 /* all calls to cpuid_count() should be made on the same cpu */
765 get_cpu();
766
767 r = -E2BIG;
768
769 entry = do_host_cpuid(array, function, 0);
770 if (!entry)
771 goto out;
772
773 switch (function) {
774 case 0:
775 /* Limited to the highest leaf implemented in KVM. */
776 entry->eax = min(entry->eax, 0x1fU);
777 break;
778 case 1:
779 cpuid_entry_override(entry, CPUID_1_EDX);
780 cpuid_entry_override(entry, CPUID_1_ECX);
781 break;
782 case 2:
783 /*
784 * On ancient CPUs, function 2 entries are STATEFUL. That is,
785 * CPUID(function=2, index=0) may return different results each
786 * time, with the least-significant byte in EAX enumerating the
787 * number of times software should do CPUID(2, 0).
788 *
789 * Modern CPUs, i.e. every CPU KVM has *ever* run on are less
790 * idiotic. Intel's SDM states that EAX & 0xff "will always
791 * return 01H. Software should ignore this value and not
792 * interpret it as an informational descriptor", while AMD's
793 * APM states that CPUID(2) is reserved.
794 *
795 * WARN if a frankenstein CPU that supports virtualization and
796 * a stateful CPUID.0x2 is encountered.
797 */
798 WARN_ON_ONCE((entry->eax & 0xff) > 1);
799 break;
800 /* functions 4 and 0x8000001d have additional index. */
801 case 4:
802 case 0x8000001d:
803 /*
804 * Read entries until the cache type in the previous entry is
805 * zero, i.e. indicates an invalid entry.
806 */
807 for (i = 1; entry->eax & 0x1f; ++i) {
808 entry = do_host_cpuid(array, function, i);
809 if (!entry)
810 goto out;
811 }
812 break;
813 case 6: /* Thermal management */
814 entry->eax = 0x4; /* allow ARAT */
815 entry->ebx = 0;
816 entry->ecx = 0;
817 entry->edx = 0;
818 break;
819 /* function 7 has additional index. */
820 case 7:
821 entry->eax = min(entry->eax, 1u);
822 cpuid_entry_override(entry, CPUID_7_0_EBX);
823 cpuid_entry_override(entry, CPUID_7_ECX);
824 cpuid_entry_override(entry, CPUID_7_EDX);
825
826 /* KVM only supports 0x7.0 and 0x7.1, capped above via min(). */
827 if (entry->eax == 1) {
828 entry = do_host_cpuid(array, function, 1);
829 if (!entry)
830 goto out;
831
832 cpuid_entry_override(entry, CPUID_7_1_EAX);
833 entry->ebx = 0;
834 entry->ecx = 0;
835 entry->edx = 0;
836 }
837 break;
838 case 9:
839 break;
840 case 0xa: { /* Architectural Performance Monitoring */
841 struct x86_pmu_capability cap;
842 union cpuid10_eax eax;
843 union cpuid10_edx edx;
844
845 perf_get_x86_pmu_capability(&cap);
846
847 /*
848 * The guest architecture pmu is only supported if the architecture
849 * pmu exists on the host and the module parameters allow it.
850 */
851 if (!cap.version || !enable_pmu)
852 memset(&cap, 0, sizeof(cap));
853
854 eax.split.version_id = min(cap.version, 2);
855 eax.split.num_counters = cap.num_counters_gp;
856 eax.split.bit_width = cap.bit_width_gp;
857 eax.split.mask_length = cap.events_mask_len;
858
859 edx.split.num_counters_fixed = min(cap.num_counters_fixed, MAX_FIXED_COUNTERS);
860 edx.split.bit_width_fixed = cap.bit_width_fixed;
861 if (cap.version)
862 edx.split.anythread_deprecated = 1;
863 edx.split.reserved1 = 0;
864 edx.split.reserved2 = 0;
865
866 entry->eax = eax.full;
867 entry->ebx = cap.events_mask;
868 entry->ecx = 0;
869 entry->edx = edx.full;
870 break;
871 }
872 /*
873 * Per Intel's SDM, the 0x1f is a superset of 0xb,
874 * thus they can be handled by common code.
875 */
876 case 0x1f:
877 case 0xb:
878 /*
879 * Populate entries until the level type (ECX[15:8]) of the
880 * previous entry is zero. Note, CPUID EAX.{0x1f,0xb}.0 is
881 * the starting entry, filled by the primary do_host_cpuid().
882 */
883 for (i = 1; entry->ecx & 0xff00; ++i) {
884 entry = do_host_cpuid(array, function, i);
885 if (!entry)
886 goto out;
887 }
888 break;
889 case 0xd: {
> 890 u64 supported_xcr0 = supported_xcr0 & xstate_get_guest_group_perm();
891
892 entry->eax &= supported_xcr0;
893 entry->ebx = xstate_required_size(supported_xcr0, false);
894 entry->ecx = entry->ebx;
895 entry->edx &= supported_xcr0 >> 32;
896 if (!supported_xcr0)
897 break;
898
899 entry = do_host_cpuid(array, function, 1);
900 if (!entry)
901 goto out;
902
903 cpuid_entry_override(entry, CPUID_D_1_EAX);
904 if (entry->eax & (F(XSAVES)|F(XSAVEC)))
905 entry->ebx = xstate_required_size(supported_xcr0 | supported_xss,
906 true);
907 else {
908 WARN_ON_ONCE(supported_xss != 0);
909 entry->ebx = 0;
910 }
911 entry->ecx &= supported_xss;
912 entry->edx &= supported_xss >> 32;
913
914 for (i = 2; i < 64; ++i) {
915 bool s_state;
916 if (supported_xcr0 & BIT_ULL(i))
917 s_state = false;
918 else if (supported_xss & BIT_ULL(i))
919 s_state = true;
920 else
921 continue;
922
923 entry = do_host_cpuid(array, function, i);
924 if (!entry)
925 goto out;
926
927 /*
928 * The supported check above should have filtered out
929 * invalid sub-leafs. Only valid sub-leafs should
930 * reach this point, and they should have a non-zero
931 * save state size. Furthermore, check whether the
932 * processor agrees with supported_xcr0/supported_xss
933 * on whether this is an XCR0- or IA32_XSS-managed area.
934 */
935 if (WARN_ON_ONCE(!entry->eax || (entry->ecx & 0x1) != s_state)) {
936 --array->nent;
937 continue;
938 }
939
940 if (!kvm_cpu_cap_has(X86_FEATURE_XFD))
941 entry->ecx &= ~BIT_ULL(2);
942 entry->edx = 0;
943 }
944 break;
945 }
946 case 0x12:
947 /* Intel SGX */
948 if (!kvm_cpu_cap_has(X86_FEATURE_SGX)) {
949 entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
950 break;
951 }
952
953 /*
954 * Index 0: Sub-features, MISCSELECT (a.k.a extended features)
955 * and max enclave sizes. The SGX sub-features and MISCSELECT
956 * are restricted by kernel and KVM capabilities (like most
957 * feature flags), while enclave size is unrestricted.
958 */
959 cpuid_entry_override(entry, CPUID_12_EAX);
960 entry->ebx &= SGX_MISC_EXINFO;
961
962 entry = do_host_cpuid(array, function, 1);
963 if (!entry)
964 goto out;
965
966 /*
967 * Index 1: SECS.ATTRIBUTES. ATTRIBUTES are restricted a la
968 * feature flags. Advertise all supported flags, including
969 * privileged attributes that require explicit opt-in from
970 * userspace. ATTRIBUTES.XFRM is not adjusted as userspace is
971 * expected to derive it from supported XCR0.
972 */
973 entry->eax &= SGX_ATTR_DEBUG | SGX_ATTR_MODE64BIT |
974 SGX_ATTR_PROVISIONKEY | SGX_ATTR_EINITTOKENKEY |
975 SGX_ATTR_KSS;
976 entry->ebx &= 0;
977 break;
978 /* Intel PT */
979 case 0x14:
980 if (!kvm_cpu_cap_has(X86_FEATURE_INTEL_PT)) {
981 entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
982 break;
983 }
984
985 for (i = 1, max_idx = entry->eax; i <= max_idx; ++i) {
986 if (!do_host_cpuid(array, function, i))
987 goto out;
988 }
989 break;
990 /* Intel AMX TILE */
991 case 0x1d:
992 if (!kvm_cpu_cap_has(X86_FEATURE_AMX_TILE)) {
993 entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
994 break;
995 }
996
997 for (i = 1, max_idx = entry->eax; i <= max_idx; ++i) {
998 if (!do_host_cpuid(array, function, i))
999 goto out;
1000 }
1001 break;
1002 case 0x1e: /* TMUL information */
1003 if (!kvm_cpu_cap_has(X86_FEATURE_AMX_TILE)) {
1004 entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
1005 break;
1006 }
1007 break;
1008 case KVM_CPUID_SIGNATURE: {
1009 const u32 *sigptr = (const u32 *)KVM_SIGNATURE;
1010 entry->eax = KVM_CPUID_FEATURES;
1011 entry->ebx = sigptr[0];
1012 entry->ecx = sigptr[1];
1013 entry->edx = sigptr[2];
1014 break;
1015 }
1016 case KVM_CPUID_FEATURES:
1017 entry->eax = (1 << KVM_FEATURE_CLOCKSOURCE) |
1018 (1 << KVM_FEATURE_NOP_IO_DELAY) |
1019 (1 << KVM_FEATURE_CLOCKSOURCE2) |
1020 (1 << KVM_FEATURE_ASYNC_PF) |
1021 (1 << KVM_FEATURE_PV_EOI) |
1022 (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT) |
1023 (1 << KVM_FEATURE_PV_UNHALT) |
1024 (1 << KVM_FEATURE_PV_TLB_FLUSH) |
1025 (1 << KVM_FEATURE_ASYNC_PF_VMEXIT) |
1026 (1 << KVM_FEATURE_PV_SEND_IPI) |
1027 (1 << KVM_FEATURE_POLL_CONTROL) |
1028 (1 << KVM_FEATURE_PV_SCHED_YIELD) |
1029 (1 << KVM_FEATURE_ASYNC_PF_INT);
1030
1031 if (sched_info_on())
1032 entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);
1033
1034 entry->ebx = 0;
1035 entry->ecx = 0;
1036 entry->edx = 0;
1037 break;
1038 case 0x80000000:
1039 entry->eax = min(entry->eax, 0x8000001f);
1040 break;
1041 case 0x80000001:
1042 cpuid_entry_override(entry, CPUID_8000_0001_EDX);
1043 cpuid_entry_override(entry, CPUID_8000_0001_ECX);
1044 break;
1045 case 0x80000006:
1046 /* L2 cache and TLB: pass through host info. */
1047 break;
1048 case 0x80000007: /* Advanced power management */
1049 /* invariant TSC is CPUID.80000007H:EDX[8] */
1050 entry->edx &= (1 << 8);
1051 /* mask against host */
1052 entry->edx &= boot_cpu_data.x86_power;
1053 entry->eax = entry->ebx = entry->ecx = 0;
1054 break;
1055 case 0x80000008: {
1056 unsigned g_phys_as = (entry->eax >> 16) & 0xff;
1057 unsigned virt_as = max((entry->eax >> 8) & 0xff, 48U);
1058 unsigned phys_as = entry->eax & 0xff;
1059
1060 /*
1061 * If TDP (NPT) is disabled use the adjusted host MAXPHYADDR as
1062 * the guest operates in the same PA space as the host, i.e.
1063 * reductions in MAXPHYADDR for memory encryption affect shadow
1064 * paging, too.
1065 *
1066 * If TDP is enabled but an explicit guest MAXPHYADDR is not
1067 * provided, use the raw bare metal MAXPHYADDR as reductions to
1068 * the HPAs do not affect GPAs.
1069 */
1070 if (!tdp_enabled)
1071 g_phys_as = boot_cpu_data.x86_phys_bits;
1072 else if (!g_phys_as)
1073 g_phys_as = phys_as;
1074
1075 entry->eax = g_phys_as | (virt_as << 8);
1076 entry->edx = 0;
1077 cpuid_entry_override(entry, CPUID_8000_0008_EBX);
1078 break;
1079 }
1080 case 0x8000000A:
1081 if (!kvm_cpu_cap_has(X86_FEATURE_SVM)) {
1082 entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
1083 break;
1084 }
1085 entry->eax = 1; /* SVM revision 1 */
1086 entry->ebx = 8; /* Lets support 8 ASIDs in case we add proper
1087 ASID emulation to nested SVM */
1088 entry->ecx = 0; /* Reserved */
1089 cpuid_entry_override(entry, CPUID_8000_000A_EDX);
1090 break;
1091 case 0x80000019:
1092 entry->ecx = entry->edx = 0;
1093 break;
1094 case 0x8000001a:
1095 case 0x8000001e:
1096 break;
1097 case 0x8000001F:
1098 if (!kvm_cpu_cap_has(X86_FEATURE_SEV)) {
1099 entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
1100 } else {
1101 cpuid_entry_override(entry, CPUID_8000_001F_EAX);
1102
1103 /*
1104 * Enumerate '0' for "PA bits reduction", the adjusted
1105 * MAXPHYADDR is enumerated directly (see 0x80000008).
1106 */
1107 entry->ebx &= ~GENMASK(11, 6);
1108 }
1109 break;
1110 /*Add support for Centaur's CPUID instruction*/
1111 case 0xC0000000:
1112 /*Just support up to 0xC0000004 now*/
1113 entry->eax = min(entry->eax, 0xC0000004);
1114 break;
1115 case 0xC0000001:
1116 cpuid_entry_override(entry, CPUID_C000_0001_EDX);
1117 break;
1118 case 3: /* Processor serial number */
1119 case 5: /* MONITOR/MWAIT */
1120 case 0xC0000002:
1121 case 0xC0000003:
1122 case 0xC0000004:
1123 default:
1124 entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
1125 break;
1126 }
1127
1128 r = 0;
1129
1130 out:
1131 put_cpu();
1132
1133 return r;
1134 }
1135

---
0-DAY CI Kernel Test Service, Intel Corporation
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Next message: Jiangfeng Xiao: "[PATCH] [PING] perf dso: Avoid copying redundant kallsyms in th buildid_dir"
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In reply to: kernel test robot: "Re: [PATCH] KVM: x86/cpuid: Exclude unpermitted xfeatures sizes at KVM_GET_SUPPORTED_CPUID"
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