[RFC PATCH v3 15/36] i386/tdx: Implement user specified tsc frequency

[Xiaoyao Li]

Reuse "-cpu,tsc-frequency=" to get user wanted tsc frequency and pass it
to 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>
---
 target/i386/kvm/kvm.c |  8 ++++++++
 target/i386/kvm/tdx.c | 18 ++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index f2d71359b59d..4a8b6e2c8797 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -806,6 +806,14 @@ static int kvm_arch_set_tsc_khz(CPUState *cs)
     int r, cur_freq;
     bool set_ioctl = false;
 
+    /*
+     * TD guest's TSC is immutable, it cannot be set/changed via
+     * KVM_SET_TSC_KHZ, but only be initialized via KVM_TDX_INIT_VM
+     */
+    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 a76c41fe5724..94a9c1ea7e9c 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -26,6 +26,9 @@
 #define TDX_TD_ATTRIBUTES_PKS               BIT_ULL(30)
 #define TDX_TD_ATTRIBUTES_PERFMON           BIT_ULL(63)
 
+#define TDX_MIN_TSC_FREQUENCY_KHZ   (100 * 1000)
+#define TDX_MAX_TSC_FREQUENCY_KHZ   (10 * 1000 * 1000)
+
 static TdxGuest *tdx_guest;
 
 /* It's valid after kvm_confidential_guest_init()->kvm_tdx_init() */
@@ -209,6 +212,20 @@ int tdx_pre_create_vcpu(CPUState *cpu)
         goto out;
     }
 
+    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;
+    }
+
     r = setup_td_guest_attributes(x86cpu);
     if (r) {
         goto out;
@@ -219,6 +236,7 @@ int tdx_pre_create_vcpu(CPUState *cpu)
 
     init_vm.cpuid = (__u64)(&cpuid_data);
     init_vm.max_vcpus = ms->smp.cpus;
+    init_vm.tsc_khz = env->tsc_khz;
     init_vm.attributes = tdx_guest->attributes;
 
     r = tdx_vm_ioctl(KVM_TDX_INIT_VM, 0, &init_vm);
-- 
2.27.0