Re: [PATCH v10 039/108] KVM: VMX: Introduce test mode related to EPT violation VE

Binbin Wu
2022-11-03T13:42:52Z

On 2022/10/30 14:22, isaku.yamahata@intel.com wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
>
> To support TDX, KVM is enhanced to operate with #VE. For TDX, KVM programs
> to inject #VE conditionally and set #VE suppress bit in EPT entry. For VMX
> case, #VE isn't used. If #VE happens for VMX, it's a bug. To be
> defensive (test that VMX case isn't broken), introduce option
> ept_violation_ve_test and when it's set, set error.
>
> Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
> arch/x86/include/asm/vmx.h | 12 +++++++
> arch/x86/kvm/vmx/vmcs.h | 5 +++
> arch/x86/kvm/vmx/vmx.c | 69 +++++++++++++++++++++++++++++++++++++-
> arch/x86/kvm/vmx/vmx.h | 6 +++-
> 4 files changed, 90 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
> index cdbf12c1a83c..752d53652007 100644
> --- a/arch/x86/include/asm/vmx.h
> +++ b/arch/x86/include/asm/vmx.h
> @@ -68,6 +68,7 @@
> #define SECONDARY_EXEC_ENCLS_EXITING VMCS_CONTROL_BIT(ENCLS_EXITING)
> #define SECONDARY_EXEC_RDSEED_EXITING VMCS_CONTROL_BIT(RDSEED_EXITING)
> #define SECONDARY_EXEC_ENABLE_PML VMCS_CONTROL_BIT(PAGE_MOD_LOGGING)
> +#define SECONDARY_EXEC_EPT_VIOLATION_VE VMCS_CONTROL_BIT(EPT_VIOLATION_VE)
> #define SECONDARY_EXEC_PT_CONCEAL_VMX VMCS_CONTROL_BIT(PT_CONCEAL_VMX)
> #define SECONDARY_EXEC_XSAVES VMCS_CONTROL_BIT(XSAVES)
> #define SECONDARY_EXEC_MODE_BASED_EPT_EXEC VMCS_CONTROL_BIT(MODE_BASED_EPT_EXEC)
> @@ -223,6 +224,8 @@ enum vmcs_field {
> VMREAD_BITMAP_HIGH = 0x00002027,
> VMWRITE_BITMAP = 0x00002028,
> VMWRITE_BITMAP_HIGH = 0x00002029,
> + VE_INFORMATION_ADDRESS = 0x0000202A,
> + VE_INFORMATION_ADDRESS_HIGH = 0x0000202B,
> XSS_EXIT_BITMAP = 0x0000202C,
> XSS_EXIT_BITMAP_HIGH = 0x0000202D,
> ENCLS_EXITING_BITMAP = 0x0000202E,
> @@ -628,4 +631,13 @@ enum vmx_l1d_flush_state {
>
> extern enum vmx_l1d_flush_state l1tf_vmx_mitigation;
>
> +struct vmx_ve_information {
> + u32 exit_reason;
> + u32 delivery;
> + u64 exit_qualification;
> + u64 guest_linear_address;
> + u64 guest_physical_address;
> + u16 eptp_index;
> +};
> +
> #endif
> diff --git a/arch/x86/kvm/vmx/vmcs.h b/arch/x86/kvm/vmx/vmcs.h
> index ac290a44a693..9277676057a7 100644
> --- a/arch/x86/kvm/vmx/vmcs.h
> +++ b/arch/x86/kvm/vmx/vmcs.h
> @@ -140,6 +140,11 @@ static inline bool is_nm_fault(u32 intr_info)
> return is_exception_n(intr_info, NM_VECTOR);
> }
>
> +static inline bool is_ve_fault(u32 intr_info)
> +{
> + return is_exception_n(intr_info, VE_VECTOR);
> +}
> +
> /* Undocumented: icebp/int1 */
> static inline bool is_icebp(u32 intr_info)
> {
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index f890191e8580..dd3fde9d3c32 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -126,6 +126,9 @@ module_param(error_on_inconsistent_vmcs_config, bool, 0444);
> static bool __read_mostly dump_invalid_vmcs = 0;
> module_param(dump_invalid_vmcs, bool, 0644);
>
> +static bool __read_mostly ept_violation_ve_test;
> +module_param(ept_violation_ve_test, bool, 0444);
> +
> #define MSR_BITMAP_MODE_X2APIC 1
> #define MSR_BITMAP_MODE_X2APIC_APICV 2
>
> @@ -783,6 +786,13 @@ void vmx_update_exception_bitmap(struct kvm_vcpu *vcpu)
>
> eb = (1u << PF_VECTOR) | (1u << UD_VECTOR) | (1u << MC_VECTOR) |
> (1u << DB_VECTOR) | (1u << AC_VECTOR);
> + /*
> + * #VE isn't used for VMX, but for TDX. To test against unexpected
> + * change related to #VE for VMX, intercept unexpected #VE and warn on
> + * it.
> + */
> + if (ept_violation_ve_test)
> + eb |= 1u << VE_VECTOR;
> /*
> * Guest access to VMware backdoor ports could legitimately
> * trigger #GP because of TSS I/O permission bitmap.
> @@ -2644,6 +2654,9 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
> &_cpu_based_2nd_exec_control))
> return -EIO;
> }
> + if (!ept_violation_ve_test)
> + _cpu_based_exec_control &= ~SECONDARY_EXEC_EPT_VIOLATION_VE;

should be _cpu_based_2nd_exec_control

> +
> #ifndef CONFIG_X86_64
> if (!(_cpu_based_2nd_exec_control &
> SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES))
> @@ -2668,6 +2681,7 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
> return -EIO;
>
> vmx_cap->ept = 0;
> + _cpu_based_2nd_exec_control &= ~SECONDARY_EXEC_EPT_VIOLATION_VE;
> }
> if (!(_cpu_based_2nd_exec_control & SECONDARY_EXEC_ENABLE_VPID) &&
> vmx_cap->vpid) {
> @@ -4510,6 +4524,7 @@ static u32 vmx_secondary_exec_control(struct vcpu_vmx *vmx)
> exec_control &= ~SECONDARY_EXEC_ENABLE_VPID;
> if (!enable_ept) {
> exec_control &= ~SECONDARY_EXEC_ENABLE_EPT;
> + exec_control &= ~SECONDARY_EXEC_EPT_VIOLATION_VE;
> enable_unrestricted_guest = 0;
> }
> if (!enable_unrestricted_guest)
> @@ -4637,8 +4652,40 @@ static void init_vmcs(struct vcpu_vmx *vmx)
>
> exec_controls_set(vmx, vmx_exec_control(vmx));
>
> - if (cpu_has_secondary_exec_ctrls())
> + if (cpu_has_secondary_exec_ctrls()) {
> secondary_exec_controls_set(vmx, vmx_secondary_exec_control(vmx));
> + if (secondary_exec_controls_get(vmx) &
> + SECONDARY_EXEC_EPT_VIOLATION_VE) {
> + if (!vmx->ve_info) {
> + /* ve_info must be page aligned. */
> + struct page *page;
> +
> + BUILD_BUG_ON(sizeof(*vmx->ve_info) > PAGE_SIZE);
> + page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
> + if (page)
> + vmx->ve_info = page_to_virt(page);
> + }
> + if (vmx->ve_info) {
> + /*
> + * Allow #VE delivery. CPU sets this field to
> + * 0xFFFFFFFF on #VE delivery. Another #VE can
> + * occur only if software clears the field.
> + */
> + vmx->ve_info->delivery = 0;
> + vmcs_write64(VE_INFORMATION_ADDRESS,
> + __pa(vmx->ve_info));
> + } else {
> + /*
> + * Because SECONDARY_EXEC_EPT_VIOLATION_VE is
> + * used only when ept_violation_ve_test is true,
> + * it's okay to go with the bit disabled.
> + */
> + pr_err("Failed to allocate ve_info. disabling EPT_VIOLATION_VE.\n");
> + secondary_exec_controls_clearbit(vmx,
> + SECONDARY_EXEC_EPT_VIOLATION_VE);
> + }
> + }
> + }
>
> if (cpu_has_tertiary_exec_ctrls())
> tertiary_exec_controls_set(vmx, vmx_tertiary_exec_control(vmx));
> @@ -5118,6 +5165,12 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
> if (is_invalid_opcode(intr_info))
> return handle_ud(vcpu);
>
> + /*
> + * #VE isn't supposed to happen. Although vcpu can send
> + */
> + if (KVM_BUG_ON(is_ve_fault(intr_info), vcpu->kvm))
> + return -EIO;
> +
> error_code = 0;
> if (intr_info & INTR_INFO_DELIVER_CODE_MASK)
> error_code = vmcs_read32(VM_EXIT_INTR_ERROR_CODE);
> @@ -6306,6 +6359,18 @@ void dump_vmcs(struct kvm_vcpu *vcpu)
> if (secondary_exec_control & SECONDARY_EXEC_ENABLE_VPID)
> pr_err("Virtual processor ID = 0x%04x\n",
> vmcs_read16(VIRTUAL_PROCESSOR_ID));
> + if (secondary_exec_control & SECONDARY_EXEC_EPT_VIOLATION_VE) {
> + struct vmx_ve_information *ve_info;
> +
> + pr_err("VE info address = 0x%016llx\n",
> + vmcs_read64(VE_INFORMATION_ADDRESS));
> + ve_info = __va(vmcs_read64(VE_INFORMATION_ADDRESS));
> + pr_err("ve_info: 0x%08x 0x%08x 0x%016llx 0x%016llx 0x%016llx 0x%04x\n",
> + ve_info->exit_reason, ve_info->delivery,
> + ve_info->exit_qualification,
> + ve_info->guest_linear_address,
> + ve_info->guest_physical_address, ve_info->eptp_index);
> + }
> }
>
> /*
> @@ -7302,6 +7367,8 @@ void vmx_vcpu_free(struct kvm_vcpu *vcpu)
> free_vpid(vmx->vpid);
> nested_vmx_free_vcpu(vcpu);
> free_loaded_vmcs(vmx->loaded_vmcs);
> + if (vmx->ve_info)
> + free_page((unsigned long)vmx->ve_info);
> }
>
> int vmx_vcpu_create(struct kvm_vcpu *vcpu)
> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
> index d49d0ace9fb8..1813caeb24d8 100644
> --- a/arch/x86/kvm/vmx/vmx.h
> +++ b/arch/x86/kvm/vmx/vmx.h
> @@ -359,6 +359,9 @@ struct vcpu_vmx {
> DECLARE_BITMAP(read, MAX_POSSIBLE_PASSTHROUGH_MSRS);
> DECLARE_BITMAP(write, MAX_POSSIBLE_PASSTHROUGH_MSRS);
> } shadow_msr_intercept;
> +
> + /* ve_info must be page aligned. */
> + struct vmx_ve_information *ve_info;
> };
>
> struct kvm_vmx {
> @@ -570,7 +573,8 @@ static inline u8 vmx_get_rvi(void)
> SECONDARY_EXEC_ENABLE_VMFUNC | \
> SECONDARY_EXEC_BUS_LOCK_DETECTION | \
> SECONDARY_EXEC_NOTIFY_VM_EXITING | \
> - SECONDARY_EXEC_ENCLS_EXITING)
> + SECONDARY_EXEC_ENCLS_EXITING | \
> + SECONDARY_EXEC_EPT_VIOLATION_VE)
>
> #define KVM_REQUIRED_VMX_TERTIARY_VM_EXEC_CONTROL 0
> #define KVM_OPTIONAL_VMX_TERTIARY_VM_EXEC_CONTROL \