qemu-kvm/kvm-i386-tdx-Implement-user-specified-tsc-frequency.patch

From a71b4e5d1ce8bcb7cf076500a1fe8871a674b03c Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Fri, 18 Jul 2025 18:03:46 +0200
Subject: [PATCH 044/115] i386/tdx: Implement user specified tsc frequency
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

RH-Author: Paolo Bonzini <pbonzini@redhat.com>
RH-MergeRequest: 391: TDX support, including attestation and device assignment
RH-Jira: RHEL-15710 RHEL-20798 RHEL-49728
RH-Acked-by: Yash Mankad <None>
RH-Acked-by: Peter Xu <peterx@redhat.com>
RH-Acked-by: David Hildenbrand <david@redhat.com>
RH-Commit: [44/115] f12a5f1a60aa8bdd69d79e31b92dcf21380b7659 (bonzini/rhel-qemu-kvm)

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>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250508150002.689633-16-xiaoyao.li@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 0e73b843616e52882940ab89e1b0e86e22be2162)
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 target/i386/kvm/kvm.c |  9 +++++++++
 target/i386/kvm/tdx.c | 25 +++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 3b71c182ab..fa61221190 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -861,6 +861,15 @@ 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 c96e8eb7b8..56ad5f599d 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -20,6 +20,9 @@
 #include "kvm_i386.h"
 #include "tdx.h"
 
+#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)
@@ -267,6 +270,28 @@ int tdx_pre_create_vcpu(CPUState *cpu, Error **errp)
         return r;
     }
 
+    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);
+       return -EINVAL;
+    }
+
+    if (env->tsc_khz % (25 * 1000)) {
+        error_setg(errp, "Invalid TSC %ld KHz, it must be multiple of 25MHz",
+                   env->tsc_khz);
+        return -EINVAL;
+    }
+
+    /* 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 %ld kHz",
+                         env->tsc_khz);
+        return r;
+    }
+
     if (tdx_guest->mrconfigid) {
         g_autofree uint8_t *data = qbase64_decode(tdx_guest->mrconfigid,
                               strlen(tdx_guest->mrconfigid), &data_len, errp);
-- 
2.50.1