[PATCH v2 21/58] i386/tdx: Implement user specified tsc frequency

[Xiaoyao Li <xiaoyao.li@intel.com>]

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 from RFC v4:
  - 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 | 24 ++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index d51067fdc12a..4a146bc42f63 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -859,6 +859,15 @@ 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 33d015a08c34..a72badfbfd65 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -32,6 +32,9 @@
                                      (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)
@@ -513,6 +516,27 @@ int tdx_pre_create_vcpu(CPUState *cpu)
         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_report("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_report("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_report("Unable to set TSC frequency to %" PRId64 " kHz", env->tsc_khz);
+        goto out;
+    }
+
     r = setup_td_guest_attributes(x86cpu);
     if (r) {
         goto out;
-- 
2.34.1