Is this the correct linux kernel code to modify - how can i make the change to emulate CPUID code and which function i need to change. thank you
#include <linux/kvm_host.h>#include <linux/export.h>#include <linux/vmalloc.h>#include <linux/uaccess.h>#include <linux/sched/stat.h>#include <asm/processor.h>#include <asm/user.h>#include <asm/fpu/xstate.h>#include "cpuid.h"#include "lapic.h"#include "mmu.h"#include "trace.h"#include "pmu.h"static u32 xstate_required_size(u64 xstate_bv, bool compacted){ int feature_bit = 0; u32 ret = XSAVE_HDR_SIZE + XSAVE_HDR_OFFSET; xstate_bv &= XFEATURE_MASK_EXTEND; while (xstate_bv) { if (xstate_bv & 0x1) { u32 eax, ebx, ecx, edx, offset; cpuid_count(0xD, feature_bit, &eax, &ebx, &ecx, &edx); offset = compacted ? ret : ebx; ret = max(ret, offset + eax); } xstate_bv >>= 1; feature_bit++; } return ret;}bool kvm_mpx_supported(void){ return ((host_xcr0 & (XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR))&& kvm_x86_ops->mpx_supported());}EXPORT_SYMBOL_GPL(kvm_mpx_supported);u64 kvm_supported_xcr0(void){ u64 xcr0 = KVM_SUPPORTED_XCR0 & host_xcr0; if (!kvm_mpx_supported()) xcr0 &= ~(XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR); return xcr0;}#define F(x) bit(X86_FEATURE_##x)/* These are scattered features in cpufeatures.h. */#define KVM_CPUID_BIT_AVX512_4VNNIW 2#define KVM_CPUID_BIT_AVX512_4FMAPS 3#define KF(x) bit(KVM_CPUID_BIT_##x)int kvm_update_cpuid(struct kvm_vcpu *vcpu){ struct kvm_cpuid_entry2 *best; struct kvm_lapic *apic = vcpu->arch.apic; best = kvm_find_cpuid_entry(vcpu, 1, 0); if (!best) return 0; /* Update OSXSAVE bit */ if (boot_cpu_has(X86_FEATURE_XSAVE) && best->function == 0x1) { best->ecx &= ~F(OSXSAVE); if (kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE)) best->ecx |= F(OSXSAVE); } best->edx &= ~F(APIC); if (vcpu->arch.apic_base & MSR_IA32_APICBASE_ENABLE) best->edx |= F(APIC); if (apic) { if (best->ecx & F(TSC_DEADLINE_TIMER)) apic->lapic_timer.timer_mode_mask = 3 << 17; else apic->lapic_timer.timer_mode_mask = 1 << 17; } best = kvm_find_cpuid_entry(vcpu, 7, 0); if (best) { /* Update OSPKE bit */ if (boot_cpu_has(X86_FEATURE_PKU) && best->function == 0x7) { best->ecx &= ~F(OSPKE); if (kvm_read_cr4_bits(vcpu, X86_CR4_PKE)) best->ecx |= F(OSPKE); } } best = kvm_find_cpuid_entry(vcpu, 0xD, 0); if (!best) { vcpu->arch.guest_supported_xcr0 = 0; vcpu->arch.guest_xstate_size = XSAVE_HDR_SIZE + XSAVE_HDR_OFFSET; } else { vcpu->arch.guest_supported_xcr0 = (best->eax | ((u64)best->edx << 32)) & kvm_supported_xcr0(); vcpu->arch.guest_xstate_size = best->ebx = xstate_required_size(vcpu->arch.xcr0, false); } best = kvm_find_cpuid_entry(vcpu, 0xD, 1); if (best && (best->eax & (F(XSAVES) | F(XSAVEC)))) best->ebx = xstate_required_size(vcpu->arch.xcr0, true); /* * The existing code assumes virtual address is 48-bit or 57-bit in the * canonical address checks; exit if it is ever changed. */ best = kvm_find_cpuid_entry(vcpu, 0x80000008, 0); if (best) { int vaddr_bits = (best->eax & 0xff00) >> 8; if (vaddr_bits != 48 && vaddr_bits != 57 && vaddr_bits != 0) return -EINVAL; } /* Update physical-address width */ vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu); kvm_mmu_reset_context(vcpu); kvm_pmu_refresh(vcpu); return 0;}static int is_efer_nx(void){ unsigned long long efer = 0; rdmsrl_safe(MSR_EFER, &efer); return efer & EFER_NX;}static void cpuid_fix_nx_cap(struct kvm_vcpu *vcpu){ int i; struct kvm_cpuid_entry2 *e, *entry; entry = NULL; for (i = 0; i < vcpu->arch.cpuid_nent; ++i) { e = &vcpu->arch.cpuid_entries[i]; if (e->function == 0x80000001) { entry = e; break; } } if (entry && (entry->edx & F(NX)) && !is_efer_nx()) { entry->edx &= ~F(NX); printk(KERN_INFO "kvm: guest NX capability removed\n"); }}int cpuid_query_maxphyaddr(struct kvm_vcpu *vcpu){ struct kvm_cpuid_entry2 *best; best = kvm_find_cpuid_entry(vcpu, 0x80000000, 0); if (!best || best->eax < 0x80000008) goto not_found; best = kvm_find_cpuid_entry(vcpu, 0x80000008, 0); if (best) return best->eax & 0xff;not_found: return 36;}EXPORT_SYMBOL_GPL(cpuid_query_maxphyaddr);/* when an old userspace process fills a new kernel module */int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid *cpuid, struct kvm_cpuid_entry __user *entries){ int r, i; struct kvm_cpuid_entry *cpuid_entries = NULL; r = -E2BIG; if (cpuid->nent > KVM_MAX_CPUID_ENTRIES) goto out; r = -ENOMEM; if (cpuid->nent) { cpuid_entries = vmalloc(sizeof(struct kvm_cpuid_entry) * cpuid->nent); if (!cpuid_entries) goto out; r = -EFAULT; if (copy_from_user(cpuid_entries, entries, cpuid->nent * sizeof(struct kvm_cpuid_entry))) goto out; } for (i = 0; i < cpuid->nent; i++) { vcpu->arch.cpuid_entries[i].function = cpuid_entries[i].function; vcpu->arch.cpuid_entries[i].eax = cpuid_entries[i].eax; vcpu->arch.cpuid_entries[i].ebx = cpuid_entries[i].ebx; vcpu->arch.cpuid_entries[i].ecx = cpuid_entries[i].ecx; vcpu->arch.cpuid_entries[i].edx = cpuid_entries[i].edx; vcpu->arch.cpuid_entries[i].index = 0; vcpu->arch.cpuid_entries[i].flags = 0; vcpu->arch.cpuid_entries[i].padding[0] = 0; vcpu->arch.cpuid_entries[i].padding[1] = 0; vcpu->arch.cpuid_entries[i].padding[2] = 0; } vcpu->arch.cpuid_nent = cpuid->nent; cpuid_fix_nx_cap(vcpu); kvm_apic_set_version(vcpu); kvm_x86_ops->cpuid_update(vcpu); r = kvm_update_cpuid(vcpu);out: vfree(cpuid_entries); return r;}int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid, struct kvm_cpuid_entry2 __user *entries){ int r; r = -E2BIG; if (cpuid->nent > KVM_MAX_CPUID_ENTRIES) goto out; r = -EFAULT; if (copy_from_user(&vcpu->arch.cpuid_entries, entries, cpuid->nent * sizeof(struct kvm_cpuid_entry2))) goto out; vcpu->arch.cpuid_nent = cpuid->nent; kvm_apic_set_version(vcpu); kvm_x86_ops->cpuid_update(vcpu); r = kvm_update_cpuid(vcpu);out: return r;}int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid, struct kvm_cpuid_entry2 __user *entries){ int r; r = -E2BIG; if (cpuid->nent < vcpu->arch.cpuid_nent) goto out; r = -EFAULT; if (copy_to_user(entries, &vcpu->arch.cpuid_entries, vcpu->arch.cpuid_nent * sizeof(struct kvm_cpuid_entry2))) goto out; return 0;out: cpuid->nent = vcpu->arch.cpuid_nent; return r;}static void cpuid_mask(u32 *word, int wordnum){ *word &= boot_cpu_data.x86_capability[wordnum];}static void do_cpuid_1_ent(struct kvm_cpuid_entry2 *entry, u32 function, u32 index){ entry->function = function; entry->index = index; cpuid_count(entry->function, entry->index,&entry->eax, &entry->ebx, &entry->ecx, &entry->edx); entry->flags = 0;}static int __do_cpuid_ent_emulated(struct kvm_cpuid_entry2 *entry, u32 func, u32 index, int *nent, int maxnent){ switch (func) { case 0: entry->eax = 1; /* only one leaf currently */++*nent; break; case 1: entry->ecx = F(MOVBE);++*nent; break; default: break; } entry->function = func; entry->index = index; return 0;}static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, u32 index, int *nent, int maxnent){ int r; unsigned f_nx = is_efer_nx() ? F(NX) : 0;#ifdef CONFIG_X86_64 unsigned f_gbpages = (kvm_x86_ops->get_lpage_level() == PT_PDPE_LEVEL) ? F(GBPAGES) : 0; unsigned f_lm = F(LM);#else unsigned f_gbpages = 0; unsigned f_lm = 0;#endif unsigned f_rdtscp = kvm_x86_ops->rdtscp_supported() ? F(RDTSCP) : 0; unsigned f_invpcid = kvm_x86_ops->invpcid_supported() ? F(INVPCID) : 0; unsigned f_mpx = kvm_mpx_supported() ? F(MPX) : 0; unsigned f_xsaves = kvm_x86_ops->xsaves_supported() ? F(XSAVES) : 0; /* cpuid 1.edx */ const u32 kvm_cpuid_1_edx_x86_features = F(FPU) | F(VME) | F(DE) | F(PSE) | F(TSC) | F(MSR) | F(PAE) | F(MCE) | F(CX8) | F(APIC) | 0 /* Reserved */ | F(SEP) | F(MTRR) | F(PGE) | F(MCA) | F(CMOV) | F(PAT) | F(PSE36) | 0 /* PSN */ | F(CLFLUSH) | 0 /* Reserved, DS, ACPI */ | F(MMX) | F(FXSR) | F(XMM) | F(XMM2) | F(SELFSNOOP) | 0 /* HTT, TM, Reserved, PBE */; /* cpuid 0x80000001.edx */ const u32 kvm_cpuid_8000_0001_edx_x86_features = F(FPU) | F(VME) | F(DE) | F(PSE) | F(TSC) | F(MSR) | F(PAE) | F(MCE) | F(CX8) | F(APIC) | 0 /* Reserved */ | F(SYSCALL) | F(MTRR) | F(PGE) | F(MCA) | F(CMOV) | F(PAT) | F(PSE36) | 0 /* Reserved */ | f_nx | 0 /* Reserved */ | F(MMXEXT) | F(MMX) | F(FXSR) | F(FXSR_OPT) | f_gbpages | f_rdtscp | 0 /* Reserved */ | f_lm | F(3DNOWEXT) | F(3DNOW); /* cpuid 1.ecx */ const u32 kvm_cpuid_1_ecx_x86_features = /* NOTE: MONITOR (and MWAIT) are emulated as NOP, * but *not* advertised to guests via CPUID ! */ F(XMM3) | F(PCLMULQDQ) | 0 /* DTES64, MONITOR */ | 0 /* DS-CPL, VMX, SMX, EST */ | 0 /* TM2 */ | F(SSSE3) | 0 /* CNXT-ID */ | 0 /* Reserved */ | F(FMA) | F(CX16) | 0 /* xTPR Update, PDCM */ | F(PCID) | 0 /* Reserved, DCA */ | F(XMM4_1) | F(XMM4_2) | F(X2APIC) | F(MOVBE) | F(POPCNT) | 0 /* Reserved*/ | F(AES) | F(XSAVE) | 0 /* OSXSAVE */ | F(AVX) | F(F16C) | F(RDRAND); /* cpuid 0x80000001.ecx */ const u32 kvm_cpuid_8000_0001_ecx_x86_features = F(LAHF_LM) | F(CMP_LEGACY) | 0 /*SVM*/ | 0 /* ExtApicSpace */ | F(CR8_LEGACY) | F(ABM) | F(SSE4A) | F(MISALIGNSSE) | F(3DNOWPREFETCH) | F(OSVW) | 0 /* IBS */ | F(XOP) | 0 /* SKINIT, WDT, LWP */ | F(FMA4) | F(TBM); /* cpuid 0xC0000001.edx */ const u32 kvm_cpuid_C000_0001_edx_x86_features = F(XSTORE) | F(XSTORE_EN) | F(XCRYPT) | F(XCRYPT_EN) | F(ACE2) | F(ACE2_EN) | F(PHE) | F(PHE_EN) | F(PMM) | F(PMM_EN); /* cpuid 7.0.ebx */ const u32 kvm_cpuid_7_0_ebx_x86_features = F(FSGSBASE) | F(BMI1) | F(HLE) | F(AVX2) | F(SMEP) | F(BMI2) | F(ERMS) | f_invpcid | F(RTM) | f_mpx | F(RDSEED) | F(ADX) | F(SMAP) | F(AVX512IFMA) | F(AVX512F) | F(AVX512PF) | F(AVX512ER) | F(AVX512CD) | F(CLFLUSHOPT) | F(CLWB) | F(AVX512DQ) | F(SHA_NI) | F(AVX512BW) | F(AVX512VL); /* cpuid 0xD.1.eax */ const u32 kvm_cpuid_D_1_eax_x86_features = F(XSAVEOPT) | F(XSAVEC) | F(XGETBV1) | f_xsaves; /* cpuid 7.0.ecx*/ const u32 kvm_cpuid_7_0_ecx_x86_features = F(AVX512VBMI) | F(LA57) | F(PKU) | 0 /*OSPKE*/ | F(AVX512_VPOPCNTDQ); /* cpuid 7.0.edx*/ const u32 kvm_cpuid_7_0_edx_x86_features = KF(AVX512_4VNNIW) | KF(AVX512_4FMAPS); /* all calls to cpuid_count() should be made on the same cpu */ get_cpu(); r = -E2BIG; if (*nent >= maxnent) goto out; do_cpuid_1_ent(entry, function, index);++*nent; switch (function) { case 0: entry->eax = min(entry->eax, (u32)0xd); break; case 1: entry->edx &= kvm_cpuid_1_edx_x86_features; cpuid_mask(&entry->edx, CPUID_1_EDX); entry->ecx &= kvm_cpuid_1_ecx_x86_features; cpuid_mask(&entry->ecx, CPUID_1_ECX); /* we support x2apic emulation even if host does not support * it since we emulate x2apic in software */ entry->ecx |= F(X2APIC); break; /* function 2 entries are STATEFUL. That is, repeated cpuid commands * may return different values. This forces us to get_cpu() before * issuing the first command, and also to emulate this annoying behavior * in kvm_emulate_cpuid() using KVM_CPUID_FLAG_STATE_READ_NEXT */ case 2: { int t, times = entry->eax & 0xff; entry->flags |= KVM_CPUID_FLAG_STATEFUL_FUNC; entry->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT; for (t = 1; t < times; ++t) { if (*nent >= maxnent) goto out; do_cpuid_1_ent(&entry[t], function, 0); entry[t].flags |= KVM_CPUID_FLAG_STATEFUL_FUNC;++*nent; } break; } /* function 4 has additional index. */ case 4: { int i, cache_type; entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX; /* read more entries until cache_type is zero */ for (i = 1; ; ++i) { if (*nent >= maxnent) goto out; cache_type = entry[i - 1].eax & 0x1f; if (!cache_type) break; do_cpuid_1_ent(&entry[i], function, i); entry[i].flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;++*nent; } break; } case 6: /* Thermal management */ entry->eax = 0x4; /* allow ARAT */ entry->ebx = 0; entry->ecx = 0; entry->edx = 0; break; case 7: { entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX; /* Mask ebx against host capability word 9 */ if (index == 0) { entry->ebx &= kvm_cpuid_7_0_ebx_x86_features; cpuid_mask(&entry->ebx, CPUID_7_0_EBX); // TSC_ADJUST is emulated entry->ebx |= F(TSC_ADJUST); entry->ecx &= kvm_cpuid_7_0_ecx_x86_features; cpuid_mask(&entry->ecx, CPUID_7_ECX); /* PKU is not yet implemented for shadow paging. */ if (!tdp_enabled || !boot_cpu_has(X86_FEATURE_OSPKE)) entry->ecx &= ~F(PKU); entry->edx &= kvm_cpuid_7_0_edx_x86_features; entry->edx &= get_scattered_cpuid_leaf(7, 0, CPUID_EDX); } else { entry->ebx = 0; entry->ecx = 0; entry->edx = 0; } entry->eax = 0; break; } case 9: break; case 0xa: { /* Architectural Performance Monitoring */ struct x86_pmu_capability cap; union cpuid10_eax eax; union cpuid10_edx edx; perf_get_x86_pmu_capability(&cap); /* * Only support guest architectural pmu on a host * with architectural pmu. */ if (!cap.version) memset(&cap, 0, sizeof(cap)); eax.split.version_id = min(cap.version, 2); eax.split.num_counters = cap.num_counters_gp; eax.split.bit_width = cap.bit_width_gp; eax.split.mask_length = cap.events_mask_len; edx.split.num_counters_fixed = cap.num_counters_fixed; edx.split.bit_width_fixed = cap.bit_width_fixed; edx.split.reserved = 0; entry->eax = eax.full; entry->ebx = cap.events_mask; entry->ecx = 0; entry->edx = edx.full; break; } /* function 0xb has additional index. */ case 0xb: { int i, level_type; entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX; /* read more entries until level_type is zero */ for (i = 1; ; ++i) { if (*nent >= maxnent) goto out; level_type = entry[i - 1].ecx & 0xff00; if (!level_type) break; do_cpuid_1_ent(&entry[i], function, i); entry[i].flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;++*nent; } break; } case 0xd: { int idx, i; u64 supported = kvm_supported_xcr0(); entry->eax &= supported; entry->ebx = xstate_required_size(supported, false); entry->ecx = entry->ebx; entry->edx &= supported >> 32; entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX; if (!supported) break; for (idx = 1, i = 1; idx < 64; ++idx) { u64 mask = ((u64)1 << idx); if (*nent >= maxnent) goto out; do_cpuid_1_ent(&entry[i], function, idx); if (idx == 1) { entry[i].eax &= kvm_cpuid_D_1_eax_x86_features; cpuid_mask(&entry[i].eax, CPUID_D_1_EAX); entry[i].ebx = 0; if (entry[i].eax & (F(XSAVES)|F(XSAVEC))) entry[i].ebx = xstate_required_size(supported, true); } else { if (entry[i].eax == 0 || !(supported & mask)) continue; if (WARN_ON_ONCE(entry[i].ecx & 1)) continue; } entry[i].ecx = 0; entry[i].edx = 0; entry[i].flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;++*nent;++i; } break; } case KVM_CPUID_SIGNATURE: { static const char signature[12] = "KVMKVMKVM\0\0"; const u32 *sigptr = (const u32 *)signature; entry->eax = KVM_CPUID_FEATURES; entry->ebx = sigptr[0]; entry->ecx = sigptr[1]; entry->edx = sigptr[2]; break; } case KVM_CPUID_FEATURES: entry->eax = (1 << KVM_FEATURE_CLOCKSOURCE) | (1 << KVM_FEATURE_NOP_IO_DELAY) | (1 << KVM_FEATURE_CLOCKSOURCE2) | (1 << KVM_FEATURE_ASYNC_PF) | (1 << KVM_FEATURE_PV_EOI) | (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT) | (1 << KVM_FEATURE_PV_UNHALT); if (sched_info_on()) entry->eax |= (1 << KVM_FEATURE_STEAL_TIME); entry->ebx = 0; entry->ecx = 0; entry->edx = 0; break; case 0x80000000: entry->eax = min(entry->eax, 0x8000001a); break; case 0x80000001: entry->edx &= kvm_cpuid_8000_0001_edx_x86_features; cpuid_mask(&entry->edx, CPUID_8000_0001_EDX); entry->ecx &= kvm_cpuid_8000_0001_ecx_x86_features; cpuid_mask(&entry->ecx, CPUID_8000_0001_ECX); break; case 0x80000007: /* Advanced power management */ /* invariant TSC is CPUID.80000007H:EDX[8] */ entry->edx &= (1 << 8); /* mask against host */ entry->edx &= boot_cpu_data.x86_power; entry->eax = entry->ebx = entry->ecx = 0; break; case 0x80000008: { unsigned g_phys_as = (entry->eax >> 16) & 0xff; unsigned virt_as = max((entry->eax >> 8) & 0xff, 48U); unsigned phys_as = entry->eax & 0xff; if (!g_phys_as) g_phys_as = phys_as; entry->eax = g_phys_as | (virt_as << 8); entry->ebx = entry->edx = 0; break; } case 0x80000019: entry->ecx = entry->edx = 0; break; case 0x8000001a: break; case 0x8000001d: break; /*Add support for Centaur's CPUID instruction*/ case 0xC0000000: /*Just support up to 0xC0000004 now*/ entry->eax = min(entry->eax, 0xC0000004); break; case 0xC0000001: entry->edx &= kvm_cpuid_C000_0001_edx_x86_features; cpuid_mask(&entry->edx, CPUID_C000_0001_EDX); break; case 3: /* Processor serial number */ case 5: /* MONITOR/MWAIT */ case 0xC0000002: case 0xC0000003: case 0xC0000004: default: entry->eax = entry->ebx = entry->ecx = entry->edx = 0; break; } kvm_x86_ops->set_supported_cpuid(function, entry); r = 0;out: put_cpu(); return r;}static int do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 func, u32 idx, int *nent, int maxnent, unsigned int type){ if (type == KVM_GET_EMULATED_CPUID) return __do_cpuid_ent_emulated(entry, func, idx, nent, maxnent); return __do_cpuid_ent(entry, func, idx, nent, maxnent);}#undef Fstruct kvm_cpuid_param { u32 func; u32 idx; bool has_leaf_count; bool (*qualifier)(const struct kvm_cpuid_param *param);};static bool is_centaur_cpu(const struct kvm_cpuid_param *param){ return boot_cpu_data.x86_vendor == X86_VENDOR_CENTAUR;}static bool sanity_check_entries(struct kvm_cpuid_entry2 __user *entries, __u32 num_entries, unsigned int ioctl_type){ int i; __u32 pad[3]; if (ioctl_type != KVM_GET_EMULATED_CPUID) return false; /* * We want to make sure that ->padding is being passed clean from * userspace in case we want to use it for something in the future. * * Sadly, this wasn't enforced for KVM_GET_SUPPORTED_CPUID and so we * have to give ourselves satisfied only with the emulated side. /me * sheds a tear. */ for (i = 0; i < num_entries; i++) { if (copy_from_user(pad, entries[i].padding, sizeof(pad))) return true; if (pad[0] || pad[1] || pad[2]) return true; } return false;}int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid, struct kvm_cpuid_entry2 __user *entries, unsigned int type){ struct kvm_cpuid_entry2 *cpuid_entries; int limit, nent = 0, r = -E2BIG, i; u32 func; static const struct kvm_cpuid_param param[] = { { .func = 0, .has_leaf_count = true }, { .func = 0x80000000, .has_leaf_count = true }, { .func = 0xC0000000, .qualifier = is_centaur_cpu, .has_leaf_count = true }, { .func = KVM_CPUID_SIGNATURE }, { .func = KVM_CPUID_FEATURES }, }; if (cpuid->nent < 1) goto out; if (cpuid->nent > KVM_MAX_CPUID_ENTRIES) cpuid->nent = KVM_MAX_CPUID_ENTRIES; if (sanity_check_entries(entries, cpuid->nent, type)) return -EINVAL; r = -ENOMEM; cpuid_entries = vzalloc(sizeof(struct kvm_cpuid_entry2) * cpuid->nent); if (!cpuid_entries) goto out; r = 0; for (i = 0; i < ARRAY_SIZE(param); i++) { const struct kvm_cpuid_param *ent = ¶m[i]; if (ent->qualifier && !ent->qualifier(ent)) continue; r = do_cpuid_ent(&cpuid_entries[nent], ent->func, ent->idx,&nent, cpuid->nent, type); if (r) goto out_free; if (!ent->has_leaf_count) continue; limit = cpuid_entries[nent - 1].eax; for (func = ent->func + 1; func <= limit && nent < cpuid->nent && r == 0; ++func) r = do_cpuid_ent(&cpuid_entries[nent], func, ent->idx,&nent, cpuid->nent, type); if (r) goto out_free; } r = -EFAULT; if (copy_to_user(entries, cpuid_entries, nent * sizeof(struct kvm_cpuid_entry2))) goto out_free; cpuid->nent = nent; r = 0;out_free: vfree(cpuid_entries);out: return r;}static int move_to_next_stateful_cpuid_entry(struct kvm_vcpu *vcpu, int i){ struct kvm_cpuid_entry2 *e = &vcpu->arch.cpuid_entries[i]; struct kvm_cpuid_entry2 *ej; int j = i; int nent = vcpu->arch.cpuid_nent; e->flags &= ~KVM_CPUID_FLAG_STATE_READ_NEXT; /* when no next entry is found, the current entry[i] is reselected */ do { j = (j + 1) % nent; ej = &vcpu->arch.cpuid_entries[j]; } while (ej->function != e->function); ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT; return j;}/* find an entry with matching function, matching index (if needed), and that * should be read next (if it's stateful) */static int is_matching_cpuid_entry(struct kvm_cpuid_entry2 *e, u32 function, u32 index){ if (e->function != function) return 0; if ((e->flags & KVM_CPUID_FLAG_SIGNIFCANT_INDEX) && e->index != index) return 0; if ((e->flags & KVM_CPUID_FLAG_STATEFUL_FUNC) && !(e->flags & KVM_CPUID_FLAG_STATE_READ_NEXT)) return 0; return 1;}struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu, u32 function, u32 index){ int i; struct kvm_cpuid_entry2 *best = NULL; for (i = 0; i < vcpu->arch.cpuid_nent; ++i) { struct kvm_cpuid_entry2 *e; e = &vcpu->arch.cpuid_entries[i]; if (is_matching_cpuid_entry(e, function, index)) { if (e->flags & KVM_CPUID_FLAG_STATEFUL_FUNC) move_to_next_stateful_cpuid_entry(vcpu, i); best = e; break; } } return best;}EXPORT_SYMBOL_GPL(kvm_find_cpuid_entry);/* * If no match is found, check whether we exceed the vCPU's limit * and return the content of the highest valid _standard_ leaf instead. * This is to satisfy the CPUID specification. */static struct kvm_cpuid_entry2* check_cpuid_limit(struct kvm_vcpu *vcpu, u32 function, u32 index){ struct kvm_cpuid_entry2 *maxlevel; maxlevel = kvm_find_cpuid_entry(vcpu, function & 0x80000000, 0); if (!maxlevel || maxlevel->eax >= function) return NULL; if (function & 0x80000000) { maxlevel = kvm_find_cpuid_entry(vcpu, 0, 0); if (!maxlevel) return NULL; } return kvm_find_cpuid_entry(vcpu, maxlevel->eax, index);}bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx, bool check_limit){ u32 function = *eax, index = *ecx; struct kvm_cpuid_entry2 *best; bool entry_found = true; best = kvm_find_cpuid_entry(vcpu, function, index); if (!best) { entry_found = false; if (!check_limit) goto out; best = check_cpuid_limit(vcpu, function, index); }out: if (best) { *eax = best->eax; *ebx = best->ebx; *ecx = best->ecx; *edx = best->edx; } else *eax = *ebx = *ecx = *edx = 0; trace_kvm_cpuid(function, *eax, *ebx, *ecx, *edx, entry_found); return entry_found;}EXPORT_SYMBOL_GPL(kvm_cpuid);int kvm_emulate_cpuid(struct kvm_vcpu *vcpu){ u32 eax, ebx, ecx, edx; if (cpuid_fault_enabled(vcpu) && !kvm_require_cpl(vcpu, 0)) return 1; eax = kvm_register_read(vcpu, VCPU_REGS_RAX); ecx = kvm_register_read(vcpu, VCPU_REGS_RCX); kvm_cpuid(vcpu, &eax, &ebx, &ecx, &edx, true); kvm_register_write(vcpu, VCPU_REGS_RAX, eax); kvm_register_write(vcpu, VCPU_REGS_RBX, ebx); kvm_register_write(vcpu, VCPU_REGS_RCX, ecx); kvm_register_write(vcpu, VCPU_REGS_RDX, edx); return kvm_skip_emulated_instruction(vcpu);}EXPORT_SYMBOL_GPL(kvm_emulate_cpuid);I want to add/edit the code to KVM inside your linux tree (Iv cloned kernel from github) , rebuild the kernel and boot into the modified kernel and run a user mode c program like
#include <stdio.h>#include <cpuid.h>#include <stdint.h> int main(int argc, char **argv) { uint32_t eax, ebx, ecx, edx; __cpuid(0x0, eax, ebx, ecx, edx); printf("CPUID(0x0).EAX=0x%x\n", eax); printf("CPUID(0x0).EBX=0x%x\n", ebx); printf("CPUID(0x0).ECX=0x%x\n", ecx); printf("CPUID(0x0).EDX=0x%x\n", edx); return 0; }To get a output like
CPUID(0x0) Brand String = GenuineIntelCPUID(0x4FFFFFFF)CPUID(0x0) Brand String = SOME TEXTCPUID(0x4FFFFFFF)