[PATCH v3 26/70] i386/tdx: Initialize TDX before creating TD vcpus

Xiaoyao Li
2023-11-15T07:18:27Z

Invoke KVM_TDX_INIT in kvm_arch_pre_create_vcpu() that KVM_TDX_INIT
configures global TD configurations, e.g. the canonical CPUID config,
and must be executed prior to creating vCPUs.

Use kvm_x86_arch_cpuid() to setup the CPUID settings for TDX VM.

Note, this doesn't address the fact that QEMU may change the CPUID
configuration when creating vCPUs, i.e. punts on refactoring QEMU to
provide a stable CPUID config prior to kvm_arch_init().

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
---
Changes in v3:
- Pass @errp in tdx_pre_create_vcpu() and pass error info to it. (Daniel)
---
accel/kvm/kvm-all.c | 9 +++++++-
target/i386/kvm/kvm.c | 9 ++++++++
target/i386/kvm/tdx-stub.c | 5 +++++
target/i386/kvm/tdx.c | 45 ++++++++++++++++++++++++++++++++++++++
target/i386/kvm/tdx.h | 4 ++++
5 files changed, 71 insertions(+), 1 deletion(-)

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 6b5f4d62f961..a92fff471b58 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -441,8 +441,15 @@ int kvm_init_vcpu(CPUState *cpu, Error **errp)

trace_kvm_init_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu));

+ /*
+ * tdx_pre_create_vcpu() may call cpu_x86_cpuid(). It in turn may call
+ * kvm_vm_ioctl(). Set cpu->kvm_state in advance to avoid NULL pointer
+ * dereference.
+ */
+ cpu->kvm_state = s;
ret = kvm_arch_pre_create_vcpu(cpu, errp);
if (ret < 0) {
+ cpu->kvm_state = NULL;
goto err;
}

@@ -450,11 +457,11 @@ int kvm_init_vcpu(CPUState *cpu, Error **errp)
if (ret < 0) {
error_setg_errno(errp, -ret, "kvm_init_vcpu: kvm_get_vcpu failed (%lu)",
kvm_arch_vcpu_id(cpu));
+ cpu->kvm_state = NULL;
goto err;
}

cpu->kvm_fd = ret;
- cpu->kvm_state = s;
cpu->vcpu_dirty = true;
cpu->dirty_pages = 0;
cpu->throttle_us_per_full = 0;
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index dafe4d262977..fc840653ceb6 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -2268,6 +2268,15 @@ int kvm_arch_init_vcpu(CPUState *cs)
return r;
}

+int kvm_arch_pre_create_vcpu(CPUState *cpu, Error **errp)
+{
+ if (is_tdx_vm()) {
+ return tdx_pre_create_vcpu(cpu, errp);
+ }
+
+ return 0;
+}
+
int kvm_arch_destroy_vcpu(CPUState *cs)
{
X86CPU *cpu = X86_CPU(cs);
diff --git a/target/i386/kvm/tdx-stub.c b/target/i386/kvm/tdx-stub.c
index 1d866d5496bf..3877d432a397 100644
--- a/target/i386/kvm/tdx-stub.c
+++ b/target/i386/kvm/tdx-stub.c
@@ -6,3 +6,8 @@ int tdx_kvm_init(MachineState *ms, Error **errp)
{
return -EINVAL;
}
+
+int tdx_pre_create_vcpu(CPUState *cpu, Error **errp)
+{
+ return -EINVAL;
+}
diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index 1f5d8117d1a9..122a37c93de3 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -467,6 +467,49 @@ int tdx_kvm_init(MachineState *ms, Error **errp)
return 0;
}

+int tdx_pre_create_vcpu(CPUState *cpu, Error **errp)
+{
+ MachineState *ms = MACHINE(qdev_get_machine());
+ X86CPU *x86cpu = X86_CPU(cpu);
+ CPUX86State *env = &x86cpu->env;
+ struct kvm_tdx_init_vm *init_vm;
+ int r = 0;
+
+ qemu_mutex_lock(&tdx_guest->lock);
+ if (tdx_guest->initialized) {
+ goto out;
+ }
+
+ init_vm = g_malloc0(sizeof(struct kvm_tdx_init_vm) +
+ sizeof(struct kvm_cpuid_entry2) * KVM_MAX_CPUID_ENTRIES);
+
+ r = kvm_vm_enable_cap(kvm_state, KVM_CAP_MAX_VCPUS, 0, ms->smp.cpus);
+ if (r < 0) {
+ error_setg(errp, "Unable to set MAX VCPUS to %d", ms->smp.cpus);
+ goto out_free;
+ }
+
+ init_vm->cpuid.nent = kvm_x86_arch_cpuid(env, init_vm->cpuid.entries, 0);
+
+ init_vm->attributes = tdx_guest->attributes;
+
+ do {
+ r = tdx_vm_ioctl(KVM_TDX_INIT_VM, 0, init_vm);
+ } while (r == -EAGAIN);
+ if (r < 0) {
+ error_setg_errno(errp, -r, "KVM_TDX_INIT_VM failed");
+ goto out_free;
+ }
+
+ tdx_guest->initialized = true;
+
+out_free:
+ g_free(init_vm);
+out:
+ qemu_mutex_unlock(&tdx_guest->lock);
+ return r;
+}
+
/* tdx guest */
OBJECT_DEFINE_TYPE_WITH_INTERFACES(TdxGuest,
tdx_guest,
@@ -479,6 +522,8 @@ static void tdx_guest_init(Object *obj)
{
TdxGuest *tdx = TDX_GUEST(obj);

+ qemu_mutex_init(&tdx->lock);
+
tdx->attributes = 0;
}

diff --git a/target/i386/kvm/tdx.h b/target/i386/kvm/tdx.h
index 06599b65b827..432077723ac5 100644
--- a/target/i386/kvm/tdx.h
+++ b/target/i386/kvm/tdx.h
@@ -17,6 +17,9 @@ typedef struct TdxGuestClass {
typedef struct TdxGuest {
ConfidentialGuestSupport parent_obj;

+ QemuMutex lock;
+
+ bool initialized;
uint64_t attributes; /* TD attributes */
} TdxGuest;

@@ -29,5 +32,6 @@ bool is_tdx_vm(void);
int tdx_kvm_init(MachineState *ms, Error **errp);
void tdx_get_supported_cpuid(uint32_t function, uint32_t index, int reg,
uint32_t *ret);
+int tdx_pre_create_vcpu(CPUState *cpu, Error **errp);

#endif /* QEMU_I386_TDX_H */
--
2.34.1