[RFC PATCH v3 08/36] i386/tdx: Adjust get_supported_cpuid() for TDX VM

[Xiaoyao Li]

For TDX, the allowable CPUID configuration differs from what KVM
reports for KVM scope via KVM_GET_SUPPORTED_CPUID.

- Some CPUID bits are not supported for TDX VM while KVM reports the
  support. Mask them off for TDX VM. e.g., CPUID_EXT_VMX, some PV
  featues.

- The supported XCR0 and XSS bits needs to be caped by tdx_caps, because
  KVM uses them to setup XFAM of TD.

Introduce tdx_get_supported_cpuid() to adjust the
kvm_arch_get_supported_cpuid() for TDX VM.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
---
 target/i386/cpu.h     |  5 +++++
 target/i386/kvm/kvm.c |  4 ++++
 target/i386/kvm/tdx.c | 39 +++++++++++++++++++++++++++++++++++++++
 target/i386/kvm/tdx.h |  2 ++
 4 files changed, 50 insertions(+)

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 5e406088a91a..7fa30f4ed7db 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -566,6 +566,11 @@ typedef enum X86Seg {
 #define ESA_FEATURE_XFD_MASK            (1U << ESA_FEATURE_XFD_BIT)
 
 
+#define XCR0_MASK       (XSTATE_FP_MASK | XSTATE_SSE_MASK | XSTATE_YMM_MASK | \
+                         XSTATE_BNDREGS_MASK | XSTATE_BNDCSR_MASK | \
+                         XSTATE_OPMASK_MASK | XSTATE_ZMM_Hi256_MASK | \
+                         XSTATE_Hi16_ZMM_MASK | XSTATE_PKRU_MASK)
+
 /* CPUID feature words */
 typedef enum FeatureWord {
     FEAT_1_EDX,         /* CPUID[1].EDX */
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 26ed5faf07b8..ddbe8f64fadb 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -486,6 +486,10 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, 
uint32_t function,
         ret |= 1U << KVM_HINTS_REALTIME;
     }
 
+    if (is_tdx_vm()) {
+        tdx_get_supported_cpuid(function, index, reg, &ret);
+    }
+
     return ret;
 }
 
diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index 846511b299f4..e4ee55f30c79 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -14,6 +14,7 @@
 #include "qemu/osdep.h"
 #include "qapi/error.h"
 #include "qom/object_interfaces.h"
+#include "standard-headers/asm-x86/kvm_para.h"
 #include "sysemu/kvm.h"
 
 #include "hw/i386/x86.h"
@@ -110,6 +111,44 @@ int tdx_kvm_init(MachineState *ms, Error **errp)
     return 0;
 }
 
+void tdx_get_supported_cpuid(uint32_t function, uint32_t index, int reg,
+                             uint32_t *ret)
+{
+    switch (function) {
+    case 1:
+        if (reg == R_ECX) {
+            *ret &= ~CPUID_EXT_VMX;
+        }
+        break;
+    case 0xd:
+        if (index == 0) {
+            if (reg == R_EAX) {
+                *ret &= (uint32_t)tdx_caps->xfam_fixed0 & XCR0_MASK;
+                *ret |= (uint32_t)tdx_caps->xfam_fixed1 & XCR0_MASK;
+            } else if (reg == R_EDX) {
+                *ret &= (tdx_caps->xfam_fixed0 & XCR0_MASK) >> 32;
+                *ret |= (tdx_caps->xfam_fixed1 & XCR0_MASK) >> 32;
+            }
+        } else if (index == 1) {
+            /* TODO: Adjust XSS when it's supported. */
+        }
+        break;
+    case KVM_CPUID_FEATURES:
+        if (reg == R_EAX) {
+            *ret &= ~((1ULL << KVM_FEATURE_CLOCKSOURCE) |
+                      (1ULL << KVM_FEATURE_CLOCKSOURCE2) |
+                      (1ULL << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT) |
+                      (1ULL << KVM_FEATURE_ASYNC_PF) |
+                      (1ULL << KVM_FEATURE_ASYNC_PF_VMEXIT) |
+                      (1ULL << KVM_FEATURE_ASYNC_PF_INT));
+        }
+        break;
+    default:
+        /* TODO: Use tdx_caps to adjust CPUID leafs. */
+        break;
+    }
+}
+
 /* tdx guest */
 OBJECT_DEFINE_TYPE_WITH_INTERFACES(TdxGuest,
                                    tdx_guest,
diff --git a/target/i386/kvm/tdx.h b/target/i386/kvm/tdx.h
index 4036ca2f3f99..06599b65b827 100644
--- a/target/i386/kvm/tdx.h
+++ b/target/i386/kvm/tdx.h
@@ -27,5 +27,7 @@ bool is_tdx_vm(void);
 #endif /* CONFIG_TDX */
 
 int tdx_kvm_init(MachineState *ms, Error **errp);
+void tdx_get_supported_cpuid(uint32_t function, uint32_t index, int reg,
+                             uint32_t *ret);
 
 #endif /* QEMU_I386_TDX_H */
-- 
2.27.0