Reuse "-cpu,tsc-frequency=" to get user wanted tsc frequency and call VM
scope VM_SET_TSC_KHZ to set the tsc frequency of TD before KVM_TDX_INIT_VM.

Besides, sanity check the tsc frequency to be in the legal range and
legal granularity (required by TDX module).

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
---
Changes in v3:
- use @errp to report error info; (Daniel)

Changes in v1:
- Use VM scope VM_SET_TSC_KHZ to set the TSC frequency of TD since KVM
  side drop the @tsc_khz field in struct kvm_tdx_init_vm
---
 target/i386/kvm/kvm.c |  9 +++++++++
 target/i386/kvm/tdx.c | 26 ++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index fc840653ceb6..d09d9f4eee94 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -795,6 +795,15 @@ static int kvm_arch_set_tsc_khz(CPUState *cs)
     int r, cur_freq;
     bool set_ioctl = false;
 
+    /*
+     * TSC of TD vcpu is immutable, it cannot be set/changed via vcpu scope
+     * VM_SET_TSC_KHZ, but only be initialized via VM scope VM_SET_TSC_KHZ
+     * before ioctl KVM_TDX_INIT_VM in tdx_pre_create_vcpu()
+     */
+    if (is_tdx_vm()) {
+        return 0;
+    }
+
     if (!env->tsc_khz) {
         return 0;
     }
diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index b70efbcab738..05ca841d0b66 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -33,6 +33,9 @@
                                      (1U << KVM_FEATURE_PV_SCHED_YIELD) | \
                                      (1U << KVM_FEATURE_MSI_EXT_DEST_ID))
 
+#define TDX_MIN_TSC_FREQUENCY_KHZ   (100 * 1000)
+#define TDX_MAX_TSC_FREQUENCY_KHZ   (10 * 1000 * 1000)
+
 #define TDX_TD_ATTRIBUTES_DEBUG             BIT_ULL(0)
 #define TDX_TD_ATTRIBUTES_SEPT_VE_DISABLE   BIT_ULL(28)
 #define TDX_TD_ATTRIBUTES_PKS               BIT_ULL(30)
@@ -559,6 +562,29 @@ int tdx_pre_create_vcpu(CPUState *cpu, Error **errp)
         goto out_free;
     }
 
+    r = -EINVAL;
+    if (env->tsc_khz && (env->tsc_khz < TDX_MIN_TSC_FREQUENCY_KHZ ||
+                         env->tsc_khz > TDX_MAX_TSC_FREQUENCY_KHZ)) {
+        error_setg(errp, "Invalid TSC %ld KHz, must specify cpu_frequency between [%d, %d] kHz",
+                   env->tsc_khz, TDX_MIN_TSC_FREQUENCY_KHZ,
+                   TDX_MAX_TSC_FREQUENCY_KHZ);
+        goto out;
+    }
+
+    if (env->tsc_khz % (25 * 1000)) {
+        error_setg(errp, "Invalid TSC %ld KHz, it must be multiple of 25MHz",
+                   env->tsc_khz);
+        goto out;
+    }
+
+    /* it's safe even env->tsc_khz is 0. KVM uses host's tsc_khz in this case */
+    r = kvm_vm_ioctl(kvm_state, KVM_SET_TSC_KHZ, env->tsc_khz);
+    if (r < 0) {
+        error_setg_errno(errp, -r, "Unable to set TSC frequency to %" PRId64 " kHz",
+                         env->tsc_khz);
+        goto out;
+    }
+
     r = setup_td_guest_attributes(x86cpu, errp);
     if (r) {
         goto out;
-- 
2.34.1