[Xen-devel] [PATCH v2 13/17] xen: vmx: handle VMEXIT from SGX enclave

[Boqun Feng <boqun.feng@xxxxxxxxx>]

From: Kai Huang <kai.huang@xxxxxxxxxxxxxxx>

VMX adds new bit to both exit_reason and GUEST_INTERRUPT_STATE to indicate
whether VMEXIT happens in Enclave. Several instructions are also invalid or
behave differently in enclave according to SDM. This patch handles those
cases.

Signed-off-by: Kai Huang <kai.huang@xxxxxxxxxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vmx.c         | 29 +++++++++++++++++++++++++++++
 xen/include/asm-x86/hvm/vmx/vmcs.h |  2 ++
 xen/include/asm-x86/hvm/vmx/vmx.h  |  2 ++
 3 files changed, 33 insertions(+)

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index c48c44565fc5..280fc82ca1ff 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -58,6 +58,7 @@
 #include <asm/mce.h>
 #include <asm/monitor.h>
 #include <public/arch-x86/cpuid.h>
+#include <asm/sgx.h>
 
 static bool_t __initdata opt_force_ept;
 boolean_param("force-ept", opt_force_ept);
@@ -3536,6 +3537,7 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
     unsigned long exit_qualification, exit_reason, idtv_info, intr_info = 0;
     unsigned int vector = 0, mode;
     struct vcpu *v = current;
+    bool_t exit_from_sgx_enclave;
 
     __vmread(GUEST_RIP,    &regs->rip);
     __vmread(GUEST_RSP,    &regs->rsp);
@@ -3561,6 +3563,11 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
 
     perfc_incra(vmexits, exit_reason);
 
+    /* We need to handle several VMEXITs if VMEXIT is from enclave. Also clear
+     * bit 27 as it is further useless. */
+    exit_from_sgx_enclave = !!(exit_reason & VMX_EXIT_REASONS_FROM_ENCLAVE);
+    exit_reason &= ~VMX_EXIT_REASONS_FROM_ENCLAVE;
+
     /* Handle the interrupt we missed before allowing any more in. */
     switch ( (uint16_t)exit_reason )
     {
@@ -4062,6 +4069,18 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
         break;
 
     case EXIT_REASON_INVD:
+       /*
+        * SDM 39.6.5 INVD Handling when Enclave Are Enabled
+        *
+        * INVD cause #GP if EPC is enabled.
+        * FIXME: WBINVD??
+        */
+        if ( exit_from_sgx_enclave )
+        {
+            hvm_inject_hw_exception(TRAP_gp_fault, 0);
+            break;
+        }
+        /* Otherwise passthrough */
     case EXIT_REASON_WBINVD:
     {
         update_guest_eip(); /* Safe: INVD, WBINVD */
@@ -4073,6 +4092,16 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
     {
         paddr_t gpa;
 
+        /*
+         * Currently EPT violation from enclave is not possible as all EPC 
pages
+         * are statically allocated to guest when guest is created. We simply
+         * crash guest in this case.
+         */
+        if ( exit_from_sgx_enclave )
+        {
+            domain_crash(v->domain);
+            break;
+        }
         __vmread(GUEST_PHYSICAL_ADDRESS, &gpa);
         __vmread(EXIT_QUALIFICATION, &exit_qualification);
         ept_handle_violation(exit_qualification, gpa);
diff --git a/xen/include/asm-x86/hvm/vmx/vmcs.h 
b/xen/include/asm-x86/hvm/vmx/vmcs.h
index f68f3d0f6801..52f137437b97 100644
--- a/xen/include/asm-x86/hvm/vmx/vmcs.h
+++ b/xen/include/asm-x86/hvm/vmx/vmcs.h
@@ -338,6 +338,8 @@ extern u64 vmx_ept_vpid_cap;
 #define VMX_INTR_SHADOW_MOV_SS          0x00000002
 #define VMX_INTR_SHADOW_SMI             0x00000004
 #define VMX_INTR_SHADOW_NMI             0x00000008
+#define VMX_INTR_ENCLAVE_INTR           0x00000010  /* VMEXIT was incident to
+                                                       enclave mode */
 
 #define VMX_BASIC_REVISION_MASK         0x7fffffff
 #define VMX_BASIC_VMCS_SIZE_MASK        (0x1fffULL << 32)
diff --git a/xen/include/asm-x86/hvm/vmx/vmx.h 
b/xen/include/asm-x86/hvm/vmx/vmx.h
index 8547de9168eb..88d0dd600500 100644
--- a/xen/include/asm-x86/hvm/vmx/vmx.h
+++ b/xen/include/asm-x86/hvm/vmx/vmx.h
@@ -158,6 +158,8 @@ static inline void pi_clear_sn(struct pi_desc *pi_desc)
  * Exit Reasons
  */
 #define VMX_EXIT_REASONS_FAILED_VMENTRY 0x80000000
+/* Bit 27 is also set if VMEXIT is from SGX enclave mode */
+#define VMX_EXIT_REASONS_FROM_ENCLAVE   0x08000000
 
 #define EXIT_REASON_EXCEPTION_NMI       0
 #define EXIT_REASON_EXTERNAL_INTERRUPT  1
-- 
2.15.0


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