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

Xiaoyao Li
2024-11-05T06:37:30Z

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 | 25 +++++++++++++++++++++++++
2 files changed, 34 insertions(+)

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,
--
2.34.1