[v7,46/52] i386/tdx: Mark the configurable bit not reported by KVM as unsupported

Commit Message

Xiaoyao Li Jan. 24, 2025, 1:20 p.m. UTC

There is no interface in KVM to report the support bits of TD guest.
QEMU has to maintain the knowledge itself. E.g., fixed0 and fixed1 are
already hardcoded in tdx_fixed0_bits and tdx_fixed1_bits.

For configurable bits, KVM might filer some due to KVM lacks the support
currently. The filtered bits need to be marked as unsupported as well.
However, there is no interface to report which configurable bit is
turned unconfigurable.

Maintain the configurable bits of TDX module in QEMU and compare with
KVM reported configurable to find the ones being turned unconfigurable
by KVM and mark them as unsupported.

Signed-off-by: Xiaoyao Li <[e-mail]>
---
 target/i386/kvm/tdx.c | 61 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 60 insertions(+), 1 deletion(-)

Patch

diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index b46e581bb40e..2b9a47020934 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -529,6 +529,50 @@  KvmCpuidInfo tdx_fixed1_bits = {
     },
 };
 
+/* TDX module 1.5.08.04.0784 on EMR */
+KvmCpuidInfo tdx_configurable_bits = {
+    .cpuid.nent = 6,
+    .entries[0] = {
+        .function = 0x1,
+        .index = 0,
+        .eax = 0x0fff3fff,
+        .ebx = 0x00ff0000,
+        .ecx = 0x31044988,
+        .edx = 0xb8400000,
+    },
+    .entries[1] = {
+        .function = 0x7,
+        .index = 0,
+        .flags = KVM_CPUID_FLAG_SIGNIFCANT_INDEX,
+        .ebx = 0xd02b9b18,
+        .ecx = 0x02417f64,
+        .edx = 0x00054010,
+    },
+    .entries[2] = {
+        .function = 0x7,
+        .index = 0x1,
+        .flags = KVM_CPUID_FLAG_SIGNIFCANT_INDEX,
+        .eax = 0x00001c30,
+    },
+    .entries[3] = {
+        .function = 0x7,
+        .index = 0x2,
+        .flags = KVM_CPUID_FLAG_SIGNIFCANT_INDEX,
+        .edx = 0x00000008,
+    },
+    .entries[4] = {
+        .function = 0x1c,
+        .index = 0x0,
+        .eax = 0x0000000b,
+    },
+    .entries[5] = {
+        .function = 0x80000008,
+        .index = 0,
+        .eax = 0x000000ff,
+        .ebx = 0x00000200,
+    },
+};
+
 typedef struct TdxAttrsMap {
     uint32_t attr_index;
     uint32_t cpuid_leaf;
@@ -621,7 +665,7 @@  static uint32_t tdx_adjust_cpuid_features(X86ConfidentialGuest *cg,
                                           uint32_t feature, uint32_t index,
                                           int reg, uint32_t value)
 {
-    struct kvm_cpuid_entry2 *e;
+    struct kvm_cpuid_entry2 *e, *e1;
     uint32_t fixed0, fixed1;
 
     switch (feature) {
@@ -653,6 +697,21 @@  static uint32_t tdx_adjust_cpuid_features(X86ConfidentialGuest *cg,
     tdx_mask_cpuid_by_attrs(feature, index, reg, &value);
     tdx_mask_cpuid_by_xfam(feature, index, reg, &value);
 
+    e = cpuid_find_entry(&tdx_caps->cpuid, feature, index);
+    if (e) {
+        e1 = cpuid_find_entry(&tdx_configurable_bits.cpuid, feature, index);
+        if (e1) {
+            uint32_t kvm_configurable = cpuid_entry_get_reg(e, reg);
+            uint32_t tdx_module_configurable = cpuid_entry_get_reg(e1, reg);
+            for (int i = 0; i < 32; i++) {
+                uint32_t f = 1U << i;
+                if (f & tdx_module_configurable && !(f & kvm_configurable)) {
+                    value &= ~f;
+                }
+            }
+        }
+    }
+
     e = cpuid_find_entry(&tdx_fixed0_bits.cpuid, feature, index);
     if (e) {
         fixed0 = cpuid_entry_get_reg(e, reg);