# linux-5.15/arch/x86/kvm/vmx/vmx_ops.h

static __always_inline unsigned long __vmcs_readl(unsigned long field)
{
	unsigned long value;

	asm volatile("1: vmread %2, %1\n\t"
		     ".byte 0x3e\n\t" /* branch taken hint */
		     "ja 3f\n\t"

		     /*
		      * VMREAD failed.  Push '0' for @fault, push the failing
		      * @field, and bounce through the trampoline to preserve
		      * volatile registers.
		      */
		     "push $0\n\t"
		     "push %2\n\t"
		     "2:call vmread_error_trampoline\n\t"

		     /*
		      * Unwind the stack.  Note, the trampoline zeros out the
		      * memory for @fault so that the result is '0' on error.
		      */
		     "pop %2\n\t"
		     "pop %1\n\t"
		     "3:\n\t"

		     /* VMREAD faulted.  As above, except push '1' for @fault. */
		     ".pushsection .fixup, \"ax\"\n\t"
		     "4: push $1\n\t"
		     "push %2\n\t"
		     "jmp 2b\n\t"
		     ".popsection\n\t"
		     _ASM_EXTABLE(1b, 4b)
		     : ASM_CALL_CONSTRAINT, "=r"(value) : "r"(field) : "cc");
	return value;
}

static __always_inline u16 vmcs_read16(unsigned long field)
{
	vmcs_check16(field);
	if (static_branch_unlikely(&enable_evmcs))
		return evmcs_read16(field);
	return __vmcs_readl(field);
}
static __always_inline unsigned long vmcs_readl(unsigned long field)
{
	vmcs_checkl(field);
	if (static_branch_unlikely(&enable_evmcs))
		return evmcs_read64(field);
	return __vmcs_readl(field);
}

# linux-5.15/arch/x86/kvm/vmx/vmx.c

static int vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
{
	int ret = __vmx_handle_exit(vcpu, exit_fastpath);

    // 获取当前VMCS的guest_rip和guest_cs字段
	printk(KERN_NOTICE "GUEST CS:RIP=%04x:0x%016lx\n",
	       vmcs_read16(GUEST_CS_SELECTOR), vmcs_readl(GUEST_RIP));
	...
}

# linux-5.15/arch/x86/kvm/cpuid.c

bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
	       u32 *ecx, u32 *edx, bool exact_only)
{
	u32 orig_function = *eax, function = *eax, index = *ecx;
	struct kvm_cpuid_entry2 *entry;
	bool exact, used_max_basic = false;

	entry = kvm_find_cpuid_entry(vcpu, function, index);
	exact = !!entry;

	if (!entry && !exact_only) {
		entry = get_out_of_range_cpuid_entry(vcpu, &function, index);
		used_max_basic = !!entry;
	}

	if (entry) {
		*eax = entry->eax;
		*ebx = entry->ebx;
		*ecx = entry->ecx;
		*edx = entry->edx;
		if (function == 7 && index == 0) {
			u64 data;
		        if (!__kvm_get_msr(vcpu, MSR_IA32_TSX_CTRL, &data, true) &&
			    (data & TSX_CTRL_CPUID_CLEAR))
				*ebx &= ~(F(RTM) | F(HLE));
		}
	} else {
		*eax = *ebx = *ecx = *edx = 0;
		/*
		 * When leaf 0BH or 1FH is defined, CL is pass-through
		 * and EDX is always the x2APIC ID, even for undefined
		 * subleaves. Index 1 will exist iff the leaf is
		 * implemented, so we pass through CL iff leaf 1
		 * exists. EDX can be copied from any existing index.
		 */
		if (function == 0xb || function == 0x1f) {
			entry = kvm_find_cpuid_entry(vcpu, function, 1);
			if (entry) {
				*ecx = index & 0xff;
				*edx = entry->edx;
			}
		}
	}
	trace_kvm_cpuid(orig_function, index, *eax, *ebx, *ecx, *edx, exact,
			used_max_basic);
	return exact;
}

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_rax_read(vcpu);
	ecx = kvm_rcx_read(vcpu);
	kvm_cpuid(vcpu, &eax, &ebx, &ecx, &edx, false);
	kvm_rax_write(vcpu, eax);
	kvm_rbx_write(vcpu, ebx);
	kvm_rcx_write(vcpu, ecx);
	kvm_rdx_write(vcpu, edx);
	return kvm_skip_emulated_instruction(vcpu);
}

bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
	       u32 *ecx, u32 *edx, bool exact_only)
{
	u32 orig_function = *eax, function = *eax, index = *ecx;
	struct kvm_cpuid_entry2 *entry;
	bool exact, used_max_basic = false;

	/*set model_id fake value*/
	const char *model_id = "modify cpuid-model for test";
	u32 cpuid_model[12];
	int c, len, i;
	len = strlen(model_id);
    memset(cpuid_model, 0, 48);
    for (i = 0; i < 48; i++) {
        if (i >= len) {
            c = '\0';
        } else {
            c = (unsigned char)model_id[i];
        }
        cpuid_model[i >> 2] |= c << (8 * (i & 3));
    }
	/*set cpuid_model fake value*/

	entry = kvm_find_cpuid_entry(vcpu, function, index);
	exact = !!entry;

	if (!entry && !exact_only) {
		entry = get_out_of_range_cpuid_entry(vcpu, &function, index);
		used_max_basic = !!entry;
	}

	if (entry) {
		*eax = entry->eax;
		*ebx = entry->ebx;
		*ecx = entry->ecx;
		*edx = entry->edx;

		/*****case model-id modify test*/
		if(function == 0x80000002 || function == 0x80000003 || function == 0x80000004){
			printk("index:0x%x, cpuid_model=0x%x", index, cpuid_model[(function - 0x80000002) * 4 + 0]);
			*eax = cpuid_model[(function - 0x80000002) * 4 + 0];
			*ebx = cpuid_model[(function - 0x80000002) * 4 + 1];
			*ecx = cpuid_model[(function - 0x80000002) * 4 + 2];
			*edx = cpuid_model[(function - 0x80000002) * 4 + 3];
		}
		/*****case model-id modify test*/
		...
}