i386: kvm: Add support for exposing PROVISIONKEY to guest

If the guest want to fully use SGX, the guest needs to be able to
access provisioning key. Add a new KVM_CAP_SGX_ATTRIBUTE to KVM to
support provisioning key to KVM guests.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Message-Id: <20210719112136.57018-14-yang.zhong@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

target/i386/cpu.c

@@ -5542,7 +5542,10 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
             *ecx |= XSTATE_FP_MASK | XSTATE_SSE_MASK;
 
             /* Access to PROVISIONKEY requires additional credentials. */
-            *eax &= ~(1U << 4);
+            if ((*eax & (1U << 4)) &&
+                !kvm_enable_sgx_provisioning(cs->kvm_state)) {
+                *eax &= ~(1U << 4);
+            }
         }
 #endif
         break;

target/i386/kvm/kvm.c

@@ -4644,6 +4644,35 @@ void kvm_arch_update_guest_debug(CPUState *cpu, struct kvm_guest_debug *dbg)
     }
 }
 
+static bool has_sgx_provisioning;
+
+static bool __kvm_enable_sgx_provisioning(KVMState *s)
+{
+    int fd, ret;
+
+    if (!kvm_vm_check_extension(s, KVM_CAP_SGX_ATTRIBUTE)) {
+        return false;
+    }
+
+    fd = qemu_open_old("/dev/sgx_provision", O_RDONLY);
+    if (fd < 0) {
+        return false;
+    }
+
+    ret = kvm_vm_enable_cap(s, KVM_CAP_SGX_ATTRIBUTE, 0, fd);
+    if (ret) {
+        error_report("Could not enable SGX PROVISIONKEY: %s", strerror(-ret));
+        exit(1);
+    }
+    close(fd);
+    return true;
+}
+
+bool kvm_enable_sgx_provisioning(KVMState *s)
+{
+    return MEMORIZE(__kvm_enable_sgx_provisioning(s), has_sgx_provisioning);
+}
+
 static bool host_supports_vmx(void)
 {
     uint32_t ecx, unused;

target/i386/kvm/kvm_i386.h

@@ -51,4 +51,6 @@ bool kvm_hyperv_expand_features(X86CPU *cpu, Error **errp);
 
 uint64_t kvm_swizzle_msi_ext_dest_id(uint64_t address);
 
+bool kvm_enable_sgx_provisioning(KVMState *s);
+
 #endif