Re: [PATCH v2 14/58] i386/tdx: Initialize TDX before creating TD vcpus

["Daniel P. Berrangé" <berrange@redhat.com>]

On Fri, Aug 18, 2023 at 05:49:57AM -0400, Xiaoyao Li wrote:
> 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>
> ---
>  accel/kvm/kvm-all.c        |  9 +++++++-
>  target/i386/kvm/kvm.c      |  8 +++++++
>  target/i386/kvm/tdx-stub.c |  5 +++++
>  target/i386/kvm/tdx.c      | 45 ++++++++++++++++++++++++++++++++++++++
>  target/i386/kvm/tdx.h      |  4 ++++
>  5 files changed, 70 insertions(+), 1 deletion(-)
> 
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index 5071af917ae0..fceec7f2a83f 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -435,10 +435,17 @@ 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);
>      if (ret < 0) {
>          error_setg_errno(errp, -ret, "%s: kvm_arch_pre_create_vcpu() failed",
>                          __func__);
> +        cpu->kvm_state = NULL;
>          goto err;
>      }
>  
> @@ -446,11 +453,11 @@ 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 9ee41fffc445..d51067fdc12a 100644
> --- a/target/i386/kvm/kvm.c
> +++ b/target/i386/kvm/kvm.c
> @@ -2331,6 +2331,14 @@ int kvm_arch_init_vcpu(CPUState *cs)
>      return r;
>  }
>  
> +int kvm_arch_pre_create_vcpu(CPUState *cpu)
> +{
> +    if (is_tdx_vm())
> +        return tdx_pre_create_vcpu(cpu);

Curly braces needed for coding style - run 'scripts/checkpatch.pl'
to validate it.

> +
> +    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..61f70cc0d1d9 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)
> +{
> +    return -EINVAL;
> +}
> diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
> index 29f50fb9529e..3d313ed46bd1 100644
> --- a/target/i386/kvm/tdx.c
> +++ b/target/i386/kvm/tdx.c
> @@ -458,6 +458,49 @@ int tdx_kvm_init(MachineState *ms, Error **errp)
>      return 0;
>  }
>  
> +int tdx_pre_create_vcpu(CPUState *cpu)

Add 'Error **errp' to this method

> +{
> +    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_report("Unable to set MAX VCPUS to %d", ms->smp.cpus);

Use error_setg / error_setg_errno in this method.

> +        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_report("KVM_TDX_INIT_VM failed %s", strerror(-r));
> +        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,
> @@ -470,6 +513,8 @@ 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..46a24ee8c7cc 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);
>  
>  #endif /* QEMU_I386_TDX_H */
> -- 
> 2.34.1
> 

With regards,
Daniel
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