On Sun, Jun 13, 2010 at 03:29:13PM +0300, Nadav Har'El wrote:
> Implement the VMREAD and VMWRITE instructions. With these instructions, L1
> can read and write to the VMCS it is holding. The values are read or written
> to the fields of the shadow_vmcs structure introduced in the previous patch.
>
> Signed-off-by: Nadav Har'El <[email protected]>
> ---
> --- .before/arch/x86/kvm/vmx.c 2010-06-13 15:01:29.000000000 +0300
> +++ .after/arch/x86/kvm/vmx.c 2010-06-13 15:01:29.000000000 +0300
> @@ -299,6 +299,42 @@ struct nested_vmx {
> int l2_vmcs_num;
> };
>
> +enum vmcs_field_type {
> + VMCS_FIELD_TYPE_U16 = 0,
> + VMCS_FIELD_TYPE_U64 = 1,
> + VMCS_FIELD_TYPE_U32 = 2,
> + VMCS_FIELD_TYPE_ULONG = 3
> +};
> +
> +#define VMCS_FIELD_LENGTH_OFFSET 13
> +#define VMCS_FIELD_LENGTH_MASK 0x6000
> +
> +static inline int vmcs_field_type(unsigned long field)
> +{
> + if (0x1 & field) /* one of the *_HIGH fields, all are 32 bit */
> + return VMCS_FIELD_TYPE_U32;
> + return (VMCS_FIELD_LENGTH_MASK & field) >> 13;
> +}
> +
> +static inline int vmcs_field_size(int field_type, struct kvm_vcpu *vcpu)
> +{
> + switch (field_type) {
> + case VMCS_FIELD_TYPE_U16:
> + return 2;
> + case VMCS_FIELD_TYPE_U32:
> + return 4;
> + case VMCS_FIELD_TYPE_U64:
> + return 8;
> + case VMCS_FIELD_TYPE_ULONG:
> +#ifdef CONFIG_X86_64
> + if (is_long_mode(vcpu))
> + return 8;
> +#endif
> + return 4;
> + }
> + return 0; /* should never happen */
> +}
> +
> struct vcpu_vmx {
> struct kvm_vcpu vcpu;
> struct list_head local_vcpus_link;
> @@ -4184,6 +4220,189 @@ static int handle_vmclear(struct kvm_vcp
> return 1;
> }
>
> +static inline bool nested_vmcs_read_any(struct kvm_vcpu *vcpu,
> + unsigned long field, u64 *ret)
> +{
> + short offset = vmcs_field_to_offset(field);
> + char *p;
> +
> + if (offset < 0)
> + return 0;
> + if (!to_vmx(vcpu)->nested.current_l2_page)
> + return 0;
> +
> + p = ((char *)(get_shadow_vmcs(vcpu))) + offset;
> +
> + switch (vmcs_field_type(field)) {
> + case VMCS_FIELD_TYPE_ULONG:
> + *ret = *((unsigned long *)p);
> + return 1;
> + case VMCS_FIELD_TYPE_U16:
> + *ret = (u16) *((unsigned long *)p);
> + return 1;
> + case VMCS_FIELD_TYPE_U32:
> + *ret = (u32) *((unsigned long *)p);
> + return 1;
> + case VMCS_FIELD_TYPE_U64:
> + *ret = *((u64 *)p);
> + return 1;
> + default:
> + return 0; /* can never happen. */
> + }
> +}
> +
> +static int handle_vmread_reg(struct kvm_vcpu *vcpu, int reg,
> + unsigned long field)
> +{
> + u64 field_value;
> + if (!nested_vmcs_read_any(vcpu, field, &field_value))
> + return 0;
> +
> +#ifdef CONFIG_X86_64
> + switch (vmcs_field_type(field)) {
> + case VMCS_FIELD_TYPE_U64: case VMCS_FIELD_TYPE_ULONG:
> + if (!is_long_mode(vcpu)) {
> + kvm_register_write(vcpu, reg+1, field_value >> 32);
> + field_value = (u32)field_value;
> + }
> + }
> +#endif
> + kvm_register_write(vcpu, reg, field_value);
> + return 1;
> +}
> +
> +static int handle_vmread_mem(struct kvm_vcpu *vcpu, gva_t gva,
> + unsigned long field)
> +{
> + u64 field_value;
> + if (!nested_vmcs_read_any(vcpu, field, &field_value))
> + return 0;
> +
> + /* It's ok to use *_system, because handle_vmread verifies cpl=0 */
> + kvm_write_guest_virt_system(gva, &field_value,
> + vmcs_field_size(vmcs_field_type(field), vcpu),
> + vcpu, NULL);
> + return 1;
> +}
> +
> +static int handle_vmread(struct kvm_vcpu *vcpu)
> +{
> + unsigned long field;
> + unsigned long exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
> + u32 vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
> + gva_t gva = 0;
> + int read_succeed;
> +
> + if (!nested_vmx_check_permission(vcpu))
> + return 1;
> +
> + if (!nested_map_current(vcpu)) {
> + printk(KERN_INFO "%s invalid shadow vmcs\n", __func__);
> + set_rflags_to_vmx_fail_invalid(vcpu);
> + return 1;
> + }
> +
> + /* decode instruction info to get the field to read and where to store
> + * its value */
> + field = kvm_register_read(vcpu, VMX_OPERAND_REG2(vmx_instruction_info));
> + if (VMX_OPERAND_IS_REG(vmx_instruction_info)) {
> + read_succeed = handle_vmread_reg(vcpu,
> + VMX_OPERAND_REG(vmx_instruction_info), field);
> + } else {
> + gva = get_vmx_mem_address(vcpu, exit_qualification,
> + vmx_instruction_info);
> + if (gva == 0)
> + return 1;
> + read_succeed = handle_vmread_mem(vcpu, gva, field);
> + }
> +
> + if (read_succeed) {
> + clear_rflags_cf_zf(vcpu);
> + skip_emulated_instruction(vcpu);
> + } else {
> + set_rflags_to_vmx_fail_valid(vcpu);
> + vmcs_write32(VM_INSTRUCTION_ERROR, 12);
VM_INSTRUCTION_ERROR is read only and when do you transfer it to vmcs12 anyway?.
I think set_rflags_to_vmx_fail_valid() should get vm_instruction_error
as a parameter and put it into vmcs12, that way you'll never forget to
provide error code on fail_valid case, compiler will remind you.
> + }
> +
> + nested_unmap_current(vcpu);
> + return 1;
> +}
> +
> +
> +static int handle_vmwrite(struct kvm_vcpu *vcpu)
> +{
> + unsigned long field;
> + u64 field_value = 0;
> + gva_t gva;
> + int field_type;
> + unsigned long exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
> + u32 vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
> + char *p;
> + short offset;
> +
> + if (!nested_vmx_check_permission(vcpu))
> + return 1;
> +
> + if (!nested_map_current(vcpu)) {
> + printk(KERN_INFO "%s invalid shadow vmcs\n", __func__);
> + set_rflags_to_vmx_fail_invalid(vcpu);
> + return 1;
> + }
> +
> + field = kvm_register_read(vcpu, VMX_OPERAND_REG2(vmx_instruction_info));
> + field_type = vmcs_field_type(field);
> +
> + offset = vmcs_field_to_offset(field);
> + if (offset < 0) {
> + set_rflags_to_vmx_fail_invalid(vcpu);
> + return 1;
> + }
> + p = ((char *) get_shadow_vmcs(vcpu)) + offset;
> +
> + if (VMX_OPERAND_IS_REG(vmx_instruction_info))
> + field_value = kvm_register_read(vcpu,
> + VMX_OPERAND_REG(vmx_instruction_info));
> + else {
> + gva = get_vmx_mem_address(vcpu, exit_qualification,
> + vmx_instruction_info);
> + if (gva == 0)
> + return 1;
> + kvm_read_guest_virt(gva, &field_value,
> + vmcs_field_size(field_type, vcpu), vcpu, NULL);
> + }
> +
What about checking that vmcs field is read only?
> + switch (field_type) {
> + case VMCS_FIELD_TYPE_U16:
> + *(u16 *)p = field_value;
> + break;
> + case VMCS_FIELD_TYPE_U32:
> + *(u32 *)p = field_value;
> + break;
> + case VMCS_FIELD_TYPE_U64:
> +#ifdef CONFIG_X86_64
> + *(unsigned long *)p = field_value;
> +#else
> + *(unsigned long *)p = field_value;
> + *(((unsigned long *)p)+1) = field_value >> 32;
> +#endif
> + break;
> + case VMCS_FIELD_TYPE_ULONG:
> + *(unsigned long *)p = field_value;
> + break;
> + default:
> + printk(KERN_INFO "%s invalid field\n", __func__);
> + set_rflags_to_vmx_fail_valid(vcpu);
> + vmcs_write32(VM_INSTRUCTION_ERROR, 12);
> + nested_unmap_current(vcpu);
> + return 1;
> + }
> +
> + clear_rflags_cf_zf(vcpu);
> + skip_emulated_instruction(vcpu);
> + nested_unmap_current(vcpu);
> + return 1;
> +}
> +
> static bool verify_vmcs12_revision(struct kvm_vcpu *vcpu, gpa_t
> guest_vmcs_addr)
> {
> bool ret;
> @@ -4548,9 +4767,9 @@ static int (*kvm_vmx_exit_handlers[])(st
> [EXIT_REASON_VMLAUNCH] = handle_vmx_insn,
> [EXIT_REASON_VMPTRLD] = handle_vmptrld,
> [EXIT_REASON_VMPTRST] = handle_vmptrst,
> - [EXIT_REASON_VMREAD] = handle_vmx_insn,
> + [EXIT_REASON_VMREAD] = handle_vmread,
> [EXIT_REASON_VMRESUME] = handle_vmx_insn,
> - [EXIT_REASON_VMWRITE] = handle_vmx_insn,
> + [EXIT_REASON_VMWRITE] = handle_vmwrite,
> [EXIT_REASON_VMOFF] = handle_vmoff,
> [EXIT_REASON_VMON] = handle_vmon,
> [EXIT_REASON_TPR_BELOW_THRESHOLD] = handle_tpr_below_threshold,
> --
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--
Gleb.
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