Re: [PATCH v8 11/18] KVM: x86: Introduce KVM_SET_PAGE_ENC_BITMAP ioctl

[Steve Rutherford <srutherford@google.com>]

On Tue, May 5, 2020 at 2:18 PM Ashish Kalra <Ashish.Kalra@amd.com> wrote:
>
> From: Brijesh Singh <Brijesh.Singh@amd.com>
>
> The ioctl can be used to set page encryption bitmap for an
> incoming guest.
>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: "Radim Krčmář" <rkrcmar@redhat.com>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: x86@kernel.org
> Cc: kvm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
> ---
>  Documentation/virt/kvm/api.rst  | 44 +++++++++++++++++++++++++++++
>  arch/x86/include/asm/kvm_host.h |  2 ++
>  arch/x86/kvm/svm/sev.c          | 50 +++++++++++++++++++++++++++++++++
>  arch/x86/kvm/svm/svm.c          |  1 +
>  arch/x86/kvm/svm/svm.h          |  1 +
>  arch/x86/kvm/x86.c              | 12 ++++++++
>  include/uapi/linux/kvm.h        |  1 +
>  7 files changed, 111 insertions(+)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index ecad84086892..fa70017ee693 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -4663,6 +4663,28 @@ or shared. The bitmap can be used during the guest migration. If the page
>  is private then the userspace need to use SEV migration commands to transmit
>  the page.
>
> +4.126 KVM_SET_PAGE_ENC_BITMAP (vm ioctl)
> +---------------------------------------
> +
> +:Capability: basic
> +:Architectures: x86
> +:Type: vm ioctl
> +:Parameters: struct kvm_page_enc_bitmap (in/out)
> +:Returns: 0 on success, -1 on error
> +
> +/* for KVM_SET_PAGE_ENC_BITMAP */
> +struct kvm_page_enc_bitmap {
> +       __u64 start_gfn;
> +       __u64 num_pages;
> +       union {
> +               void __user *enc_bitmap; /* one bit per page */
> +               __u64 padding2;
> +       };
> +};
> +
> +During the guest live migration the outgoing guest exports its page encryption
> +bitmap, the KVM_SET_PAGE_ENC_BITMAP can be used to build the page encryption
> +bitmap for an incoming guest.
>
>  4.125 KVM_S390_PV_COMMAND
>  -------------------------
> @@ -4717,6 +4739,28 @@ KVM_PV_VM_VERIFY
>    Verify the integrity of the unpacked image. Only if this succeeds,
>    KVM is allowed to start protected VCPUs.
>
> +4.126 KVM_SET_PAGE_ENC_BITMAP (vm ioctl)
> +---------------------------------------
> +
> +:Capability: basic
> +:Architectures: x86
> +:Type: vm ioctl
> +:Parameters: struct kvm_page_enc_bitmap (in/out)
> +:Returns: 0 on success, -1 on error
> +
> +/* for KVM_SET_PAGE_ENC_BITMAP */
> +struct kvm_page_enc_bitmap {
> +       __u64 start_gfn;
> +       __u64 num_pages;
> +       union {
> +               void __user *enc_bitmap; /* one bit per page */
> +               __u64 padding2;
> +       };
> +};
> +
> +During the guest live migration the outgoing guest exports its page encryption
> +bitmap, the KVM_SET_PAGE_ENC_BITMAP can be used to build the page encryption
> +bitmap for an incoming guest.
>
>  5. The kvm_run structure
>  ========================
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 9e428befb6a4..fc74144d5ab0 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1258,6 +1258,8 @@ struct kvm_x86_ops {
>                                   unsigned long sz, unsigned long mode);
>         int (*get_page_enc_bitmap)(struct kvm *kvm,
>                                 struct kvm_page_enc_bitmap *bmap);
> +       int (*set_page_enc_bitmap)(struct kvm *kvm,
> +                               struct kvm_page_enc_bitmap *bmap);
>  };
>
>  struct kvm_x86_init_ops {
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 387045902470..30efc1068707 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1504,6 +1504,56 @@ int svm_get_page_enc_bitmap(struct kvm *kvm,
>         return ret;
>  }
>
> +int svm_set_page_enc_bitmap(struct kvm *kvm,
> +                                  struct kvm_page_enc_bitmap *bmap)
> +{
> +       struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> +       unsigned long gfn_start, gfn_end;
> +       unsigned long *bitmap;
> +       unsigned long sz;
> +       int ret;
> +
> +       if (!sev_guest(kvm))
> +               return -ENOTTY;
> +       /* special case of resetting the complete bitmap */
> +       if (!bmap->enc_bitmap) {
> +               mutex_lock(&kvm->lock);
> +               /* by default all pages are marked encrypted */
> +               if (sev->page_enc_bmap_size)
> +                       bitmap_fill(sev->page_enc_bmap,
> +                                   sev->page_enc_bmap_size);
> +               mutex_unlock(&kvm->lock);
> +               return 0;
> +       }
>
> +
> +       gfn_start = bmap->start_gfn;
> +       gfn_end = gfn_start + bmap->num_pages;
> +
> +       sz = ALIGN(bmap->num_pages, BITS_PER_LONG) / 8;
> +       bitmap = kmalloc(sz, GFP_KERNEL);
> +       if (!bitmap)
> +               return -ENOMEM;
> +
> +       ret = -EFAULT;
> +       if (copy_from_user(bitmap, bmap->enc_bitmap, sz))
> +               goto out;
> +
> +       mutex_lock(&kvm->lock);
> +       ret = sev_resize_page_enc_bitmap(kvm, gfn_end);
> +       if (ret)
> +               goto unlock;
> +
> +       bitmap_copy(sev->page_enc_bmap + BIT_WORD(gfn_start), bitmap,
> +                   (gfn_end - gfn_start));

I *think* this assumes that gfn_start is a multiple of 8. I'm not
certain I have a clean suggestion for fixing this, other than
advertising that this is an expectation, and returning an error if
that is not true.

If I'm reading bitmap_copy correctly, I also think it assumes all
bitmaps have lengths that are unsigned long aligned, which surprised
me.
>
> +
> +       ret = 0;
> +unlock:
> +       mutex_unlock(&kvm->lock);
> +out:
> +       kfree(bitmap);
> +       return ret;
> +}
> +
>  int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
>  {
>         struct kvm_sev_cmd sev_cmd;
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 588709a9f68e..501e82f5593c 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4017,6 +4017,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
>
>         .page_enc_status_hc = svm_page_enc_status_hc,
>         .get_page_enc_bitmap = svm_get_page_enc_bitmap,
> +       .set_page_enc_bitmap = svm_set_page_enc_bitmap,
>  };
>
>  static struct kvm_x86_init_ops svm_init_ops __initdata = {
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index f087fa7b380c..2ebdcce50312 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -405,6 +405,7 @@ int nested_svm_exit_special(struct vcpu_svm *svm);
>  int svm_page_enc_status_hc(struct kvm *kvm, unsigned long gpa,
>                                   unsigned long npages, unsigned long enc);
>  int svm_get_page_enc_bitmap(struct kvm *kvm, struct kvm_page_enc_bitmap *bmap);
> +int svm_set_page_enc_bitmap(struct kvm *kvm, struct kvm_page_enc_bitmap *bmap);
>
>  /* avic.c */
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 937797cfaf9a..c4166d7a0493 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5220,6 +5220,18 @@ long kvm_arch_vm_ioctl(struct file *filp,
>                         r = kvm_x86_ops.get_page_enc_bitmap(kvm, &bitmap);
>                 break;
>         }
> +       case KVM_SET_PAGE_ENC_BITMAP: {
> +               struct kvm_page_enc_bitmap bitmap;
> +
> +               r = -EFAULT;
> +               if (copy_from_user(&bitmap, argp, sizeof(bitmap)))
> +                       goto out;
> +
> +               r = -ENOTTY;
> +               if (kvm_x86_ops.set_page_enc_bitmap)
> +                       r = kvm_x86_ops.set_page_enc_bitmap(kvm, &bitmap);
> +               break;
> +       }
>         default:
>                 r = -ENOTTY;
>         }
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index af62f2afaa5d..2798b17484d0 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1529,6 +1529,7 @@ struct kvm_pv_cmd {
>  #define KVM_S390_PV_COMMAND            _IOWR(KVMIO, 0xc5, struct kvm_pv_cmd)
>
>  #define KVM_GET_PAGE_ENC_BITMAP        _IOW(KVMIO, 0xc6, struct kvm_page_enc_bitmap)
> +#define KVM_SET_PAGE_ENC_BITMAP        _IOW(KVMIO, 0xc7, struct kvm_page_enc_bitmap)
>
>  /* Secure Encrypted Virtualization command */
>  enum sev_cmd_id {
> --
> 2.17.1
>

Otherwise, this looks good to me. Thanks for merging the ioctls together.

Reviewed-by: Steve Rutherford <srutherford@google.com>