Re: [RFC PATCH 3/5] KVM: TDX: Add base implementation for tdx_vm_move_enc_context_from

[Zhi Wang <zhi.wang.linux@gmail.com>]

On Thu, 27 Apr 2023 14:25:41 -0700
Sagi Shahar <sagis@google.com> wrote:

> On Tue, Apr 18, 2023 at 11:34 PM Zhi Wang <zhi.wang.linux@gmail.com> wrote:
> >
> > On Tue, 18 Apr 2023 10:47:44 -0700
> > Sagi Shahar <sagis@google.com> wrote:
> >
> > > On Mon, Apr 17, 2023 at 11:28 PM Zhi Wang <zhi.wang.linux@gmail.com> wrote:
> > > >
> > > > On Fri,  7 Apr 2023 20:19:19 +0000
> > > > Sagi Shahar <sagis@google.com> wrote:
> > > >
> > > > Is there any reaon that TDX doesn't need .vm_copy_enc_context_from? Or it is
> > > > going to be deprecated? The patch comments needs to be refined according to
> > > > Sean's KVM x86 maintainer book.
> > >
> > > To clarify, there are 2 types of migrations. live migration (between
> > > different hosts) and intra-host (between kvm instances in the same
> > > host) migration. This patchset deals with intra-host migration and
> > > doesn't add support for live migration.
> > >
> > > vm_copy_enc_context_from is currently used for setting up the
> > > migration helper for SEV live migration and therefore it is currently
> > > not needed in this patcheset.
> >
> > Out of curiosity, Is this the migration helper you mentioned here also
> > a SEV VM?
> 
> I'm not that familiar with SEV migration but from what I understand
> the answer is "not exactly".
> It's a guest process that runs as part of the SEV VM firmware.
> 
> There's some public information about it here:
> https://lpc.events/event/11/contributions/958/attachments/769/1448/Live%20migration%20of%20confidential%20guests_LPC2021.pdf

Thanks so much for the information. I spent some time on reading and digging
around it didn't talk about how the callback will be used. It would be nice
to see the whole picture then I guess I will have more comments. 

> > >
> > > >
> > > > > This should mostly match the logic in sev_vm_move_enc_context_from.
> > > > >
> > > > > Signed-off-by: Sagi Shahar <sagis@google.com>
> > > > > ---
> > > > >  arch/x86/kvm/vmx/main.c    | 10 +++++++
> > > > >  arch/x86/kvm/vmx/tdx.c     | 56 ++++++++++++++++++++++++++++++++++++++
> > > > >  arch/x86/kvm/vmx/tdx.h     |  2 ++
> > > > >  arch/x86/kvm/vmx/x86_ops.h |  5 ++++
> > > > >  4 files changed, 73 insertions(+)
> > > > >
> > > > > diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
> > > > > index 5b64fe5404958..9d5d0ac465bf6 100644
> > > > > --- a/arch/x86/kvm/vmx/main.c
> > > > > +++ b/arch/x86/kvm/vmx/main.c
> > > > > @@ -979,6 +979,14 @@ static int vt_vcpu_mem_enc_ioctl(struct kvm_vcpu *vcpu, void __user *argp)
> > > > >       return tdx_vcpu_ioctl(vcpu, argp);
> > > > >  }
> > > > >
> > > > > +static int vt_move_enc_context_from(struct kvm *kvm, unsigned int source_fd)
> > > > > +{
> > > > > +     if (!is_td(kvm))
> > > > > +             return -ENOTTY;
> > > > > +
> > > > > +     return tdx_vm_move_enc_context_from(kvm, source_fd);
> > > > > +}
> > > > > +
> > > > >  #define VMX_REQUIRED_APICV_INHIBITS                 \
> > > > >  (                                                   \
> > > > >         BIT(APICV_INHIBIT_REASON_DISABLE)|           \
> > > > > @@ -1141,6 +1149,8 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
> > > > >       .dev_mem_enc_ioctl = tdx_dev_ioctl,
> > > > >       .mem_enc_ioctl = vt_mem_enc_ioctl,
> > > > >       .vcpu_mem_enc_ioctl = vt_vcpu_mem_enc_ioctl,
> > > > > +
> > > > > +     .vm_move_enc_context_from = vt_move_enc_context_from,
> > > > >  };
> > > > >
> > > > >  struct kvm_x86_init_ops vt_init_ops __initdata = {
> > > > > diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> > > > > index 8af7e4e81c860..0999a6d827c99 100644
> > > > > --- a/arch/x86/kvm/vmx/tdx.c
> > > > > +++ b/arch/x86/kvm/vmx/tdx.c
> > > > > @@ -2826,3 +2826,59 @@ int __init tdx_init(void)
> > > > >               INIT_LIST_HEAD(&per_cpu(associated_tdvcpus, cpu));
> > > > >       return 0;
> > > > >  }
> > > > > +
> > > > > +static __always_inline bool tdx_guest(struct kvm *kvm)
> > > > > +{
> > > > > +     struct kvm_tdx *tdx_kvm = to_kvm_tdx(kvm);
> > > > > +
> > > > > +     return tdx_kvm->finalized;
> > > > > +}
> > > > > +
> > > > > +static int tdx_migrate_from(struct kvm *dst, struct kvm *src)
> > > > > +{
> > > > > +     return -EINVAL;
> > > > > +}
> > > > > +
> > > > > +int tdx_vm_move_enc_context_from(struct kvm *kvm, unsigned int source_fd)
> > > > > +{
> > > > > +     struct kvm_tdx *dst_tdx = to_kvm_tdx(kvm);
> > > > > +     struct file *src_kvm_file;
> > > > > +     struct kvm_tdx *src_tdx;
> > > > > +     struct kvm *src_kvm;
> > > > > +     int ret;
> > > > > +
> > > > > +     src_kvm_file = fget(source_fd);
> > > > > +     if (!file_is_kvm(src_kvm_file)) {
> > > > > +             ret = -EBADF;
> > > > > +             goto out_fput;
> > > > > +     }
> > > > > +     src_kvm = src_kvm_file->private_data;
> > > > > +     src_tdx = to_kvm_tdx(src_kvm);
> > > > > +
> > > > > +     ret = pre_move_enc_context_from(kvm, src_kvm,
> > > > > +                                     &dst_tdx->migration_in_progress,
> > > > > +                                     &src_tdx->migration_in_progress);
> > > > > +     if (ret)
> > > > > +             goto out_fput;
> > > > > +
> > > > > +     if (tdx_guest(kvm) || !tdx_guest(src_kvm)) {
> > > > > +             ret = -EINVAL;
> > > > > +             goto out_post;
> > > > > +     }
> > > > > +
> > > > > +     ret = tdx_migrate_from(kvm, src_kvm);
> > > > > +     if (ret)
> > > > > +             goto out_post;
> > > > > +
> > > > > +     kvm_vm_dead(src_kvm);
> > > > > +     ret = 0;
> > > > > +
> > > > > +out_post:
> > > > > +     post_move_enc_context_from(kvm, src_kvm,
> > > > > +                              &dst_tdx->migration_in_progress,
> > > > > +                              &src_tdx->migration_in_progress);
> > > > > +out_fput:
> > > > > +     if (src_kvm_file)
> > > > > +             fput(src_kvm_file);
> > > > > +     return ret;
> > > > > +}
> > > > > diff --git a/arch/x86/kvm/vmx/tdx.h b/arch/x86/kvm/vmx/tdx.h
> > > > > index 71818c5001862..21b7e710be1fd 100644
> > > > > --- a/arch/x86/kvm/vmx/tdx.h
> > > > > +++ b/arch/x86/kvm/vmx/tdx.h
> > > > > @@ -24,6 +24,8 @@ struct kvm_tdx {
> > > > >       atomic_t tdh_mem_track;
> > > > >
> > > > >       u64 tsc_offset;
> > > > > +
> > > > > +     atomic_t migration_in_progress;
> > > > >  };
> > > > >
> > > > >  union tdx_exit_reason {
> > > > > diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
> > > > > index d049e0c72ed0c..275f5d75e9bf1 100644
> > > > > --- a/arch/x86/kvm/vmx/x86_ops.h
> > > > > +++ b/arch/x86/kvm/vmx/x86_ops.h
> > > > > @@ -187,6 +187,8 @@ int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp);
> > > > >  void tdx_flush_tlb(struct kvm_vcpu *vcpu);
> > > > >  int tdx_sept_tlb_remote_flush(struct kvm *kvm);
> > > > >  void tdx_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa, int root_level);
> > > > > +
> > > > > +int tdx_vm_move_enc_context_from(struct kvm *kvm, unsigned int source_fd);
> > > > >  #else
> > > > >  static inline int tdx_init(void) { return 0; };
> > > > >  static inline int tdx_hardware_setup(struct kvm_x86_ops *x86_ops) { return -ENOSYS; }
> > > > > @@ -241,6 +243,9 @@ static inline int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp) { ret
> > > > >  static inline void tdx_flush_tlb(struct kvm_vcpu *vcpu) {}
> > > > >  static inline int tdx_sept_tlb_remote_flush(struct kvm *kvm) { return 0; }
> > > > >  static inline void tdx_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa, int root_level) {}
> > > > > +
> > > > > +static inline int tdx_vm_move_enc_context_from(struct kvm *kvm, u
> > > > > +                                            nsigned int source_fd) { return -EOPNOTSUPP; }
> > > > >  #endif
> > > > >
> > > > >  #if defined(CONFIG_INTEL_TDX_HOST) && defined(CONFIG_KVM_SMM)
> > > >
> >