[v6,16/60] i386/tdx: Implement user specified tsc frequency

Commit Message

Xiaoyao Li Nov. 5, 2024, 6:23 a.m. UTC

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 <[e-mail]>
Acked-by: Gerd Hoffmann <[e-mail]>
---
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 | 25 +++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

Patch

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index db676c1336ab..4fafc003e9a7 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -872,6 +872,15 @@  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 94b9be62c5dd..4193211c3190 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -21,6 +21,9 @@ 
 #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)
@@ -247,6 +250,28 @@  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;
+    }
+
 #define SHA384_DIGEST_SIZE  48
     if (tdx_guest->mrconfigid) {
         g_autofree uint8_t *data = qbase64_decode(tdx_guest->mrconfigid,