[RFC PATCH v4 13/36] i386/tdx: Validate TD attributes

[Xiaoyao Li <xiaoyao.li@xxxxxxxxx>]

Validate TD attributes with tdx_caps that fixed-0 bits must be zero and
fixed-1 bits must be set.

Besides, sanity check the attribute bits that have not been supported by
QEMU yet. e.g., debug bit, it will be allowed in the future when debug
TD support lands in QEMU.

Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
---
 target/i386/kvm/tdx.c | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index e9c6e6fb396c..9f2cdf640b5c 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -31,6 +31,7 @@
                                      (1ULL << KVM_FEATURE_PV_SCHED_YIELD) | \
                                      (1ULL << KVM_FEATURE_MSI_EXT_DEST_ID))
 
+#define TDX_TD_ATTRIBUTES_DEBUG             BIT_ULL(0)
 #define TDX_TD_ATTRIBUTES_PKS               BIT_ULL(30)
 #define TDX_TD_ATTRIBUTES_PERFMON           BIT_ULL(63)
 
@@ -169,13 +170,32 @@ void tdx_get_supported_cpuid(uint32_t function, uint32_t index, int reg,
     }
 }
 
-static void setup_td_guest_attributes(X86CPU *x86cpu)
+static int tdx_validate_attributes(TdxGuest *tdx)
+{
+    if (((tdx->attributes & tdx_caps->attrs_fixed0) | tdx_caps->attrs_fixed1) !=
+        tdx->attributes) {
+            error_report("Invalid attributes 0x%lx for TDX VM (fixed0 0x%llx, fixed1 0x%llx)",
+                          tdx->attributes, tdx_caps->attrs_fixed0, tdx_caps->attrs_fixed1);
+            return -EINVAL;
+    }
+
+    if (tdx->attributes & TDX_TD_ATTRIBUTES_DEBUG) {
+        error_report("Current QEMU doesn't support attributes.debug[bit 0] for TDX VM");
+        return -EINVAL;
+    }
+
+    return 0;
+}
+
+static int setup_td_guest_attributes(X86CPU *x86cpu)
 {
     CPUX86State *env = &x86cpu->env;
 
     tdx_guest->attributes |= (env->features[FEAT_7_0_ECX] & CPUID_7_0_ECX_PKS) ?
                              TDX_TD_ATTRIBUTES_PKS : 0;
     tdx_guest->attributes |= x86cpu->enable_pmu ? TDX_TD_ATTRIBUTES_PERFMON : 0;
+
+    return tdx_validate_attributes(tdx_guest);
 }
 
 int tdx_pre_create_vcpu(CPUState *cpu)
@@ -191,7 +211,10 @@ int tdx_pre_create_vcpu(CPUState *cpu)
         goto out;
     }
 
-    setup_td_guest_attributes(x86cpu);
+    r = setup_td_guest_attributes(x86cpu);
+    if (r) {
+        goto out;
+    }
 
     memset(&init_vm, 0, sizeof(init_vm));
     init_vm.cpuid.nent = kvm_x86_arch_cpuid(env, init_vm.entries, 0);
-- 
2.27.0