[PATCH v9 2/7] KVM: VMX: Define CET VMCS fields and #CP flag

[Yang Weijiang]

CET(Control-flow Enforcement Technology) is an upcoming Intel(R)
processor feature that blocks Return/Jump-Oriented Programming(ROP)
attacks. It provides the following capabilities to defend
against ROP/JOP style control-flow subversion attacks:

Shadow Stack (SHSTK):
  A second stack for program which is used exclusively for
  control transfer operations.

Indirect Branch Tracking (IBT):
  Code branching protection to defend against jump/call oriented
  programming.

Several new CET MSRs are defined in kernel to support CET:
  MSR_IA32_{U,S}_CET: Controls the CET settings for user
                      mode and suervisor mode respectively.

  MSR_IA32_PL{0,1,2,3}_SSP: Stores shadow stack pointers for
                            CPL-0,1,2,3 level respectively.

  MSR_IA32_INT_SSP_TAB: Stores base address of shadow stack
                        pointer table.

Two XSAVES state bits are introduced for CET:
  IA32_XSS:[bit 11]: For saving/restoring user mode CET states
  IA32_XSS:[bit 12]: For saving/restoring supervisor mode CET states.

Six VMCS fields are introduced for CET:
  {HOST,GUEST}_S_CET: Stores CET settings for supervisor mode.
  {HOST,GUEST}_SSP: Stores shadow stack pointer for supervisor mode.
  {HOST,GUEST}_INTR_SSP_TABLE: Stores base address of shadow stack pointer
                               table.

If VM_EXIT_LOAD_HOST_CET_STATE = 1, the host's CET MSRs are restored
from below VMCS fields at VM-Exit:
  HOST_S_CET
  HOST_SSP
  HOST_INTR_SSP_TABLE

If VM_ENTRY_LOAD_GUEST_CET_STATE = 1, the guest's CET MSRs are loaded
from below VMCS fields at VM-Entry:
  GUEST_S_CET
  GUEST_SSP
  GUEST_INTR_SSP_TABLE

Co-developed-by: Zhang Yi Z <yi.z.zhang@xxxxxxxxxxxxxxx>
Signed-off-by: Zhang Yi Z <yi.z.zhang@xxxxxxxxxxxxxxx>
Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
 arch/x86/include/asm/vmx.h      | 8 ++++++++
 arch/x86/include/uapi/asm/kvm.h | 1 +
 arch/x86/kvm/x86.c              | 1 +
 arch/x86/kvm/x86.h              | 5 +++--
 4 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 1835767aa335..5b641c30e1b8 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -91,6 +91,7 @@
 #define VM_EXIT_CLEAR_BNDCFGS                   0x00800000
 #define VM_EXIT_PT_CONCEAL_PIP			0x01000000
 #define VM_EXIT_CLEAR_IA32_RTIT_CTL		0x02000000
+#define VM_EXIT_LOAD_HOST_CET_STATE             0x10000000
 
 #define VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR	0x00036dff
 
@@ -104,6 +105,7 @@
 #define VM_ENTRY_LOAD_BNDCFGS                   0x00010000
 #define VM_ENTRY_PT_CONCEAL_PIP			0x00020000
 #define VM_ENTRY_LOAD_IA32_RTIT_CTL		0x00040000
+#define VM_ENTRY_LOAD_GUEST_CET_STATE           0x00100000
 
 #define VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR	0x000011ff
 
@@ -323,6 +325,9 @@ enum vmcs_field {
 	GUEST_PENDING_DBG_EXCEPTIONS    = 0x00006822,
 	GUEST_SYSENTER_ESP              = 0x00006824,
 	GUEST_SYSENTER_EIP              = 0x00006826,
+	GUEST_S_CET                     = 0x00006828,
+	GUEST_SSP                       = 0x0000682a,
+	GUEST_INTR_SSP_TABLE            = 0x0000682c,
 	HOST_CR0                        = 0x00006c00,
 	HOST_CR3                        = 0x00006c02,
 	HOST_CR4                        = 0x00006c04,
@@ -335,6 +340,9 @@ enum vmcs_field {
 	HOST_IA32_SYSENTER_EIP          = 0x00006c12,
 	HOST_RSP                        = 0x00006c14,
 	HOST_RIP                        = 0x00006c16,
+	HOST_S_CET                      = 0x00006c18,
+	HOST_SSP                        = 0x00006c1a,
+	HOST_INTR_SSP_TABLE             = 0x00006c1c
 };
 
 /*
diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index 503d3f42da16..e68d6b448730 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -31,6 +31,7 @@
 #define MC_VECTOR 18
 #define XM_VECTOR 19
 #define VE_VECTOR 20
+#define CP_VECTOR 21
 
 /* Select x86 specific features in <linux/kvm.h> */
 #define __KVM_HAVE_PIT
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5d530521f11d..a9b1140d0508 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -379,6 +379,7 @@ static int exception_class(int vector)
 	case NP_VECTOR:
 	case SS_VECTOR:
 	case GP_VECTOR:
+	case CP_VECTOR:
 		return EXCPT_CONTRIBUTORY;
 	default:
 		break;
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index c29783afebed..402dea669619 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -114,7 +114,7 @@ static inline bool x86_exception_has_error_code(unsigned int vector)
 {
 	static u32 exception_has_error_code = BIT(DF_VECTOR) | BIT(TS_VECTOR) |
 			BIT(NP_VECTOR) | BIT(SS_VECTOR) | BIT(GP_VECTOR) |
-			BIT(PF_VECTOR) | BIT(AC_VECTOR);
+			BIT(PF_VECTOR) | BIT(AC_VECTOR) | BIT(CP_VECTOR);
 
 	return (1U << vector) & exception_has_error_code;
 }
@@ -298,7 +298,8 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, unsigned long cr2,
  * In future, applicable XSS state bits can be added here
  * to make them available to KVM and guest.
  */
-#define KVM_SUPPORTED_XSS	0
+#define KVM_SUPPORTED_XSS	(XFEATURE_MASK_CET_USER \
+				| XFEATURE_MASK_CET_KERNEL)
 
 extern u64 host_xcr0;
 
-- 
2.17.2