[RFC,v2,00/11] Add AMD SEV guest live migration support

Message

Brijesh Singh June 20, 2019, 4:38 p.m. UTC

The series add support for AMD SEV guest live migration commands. To protect the
confidentiality of an SEV protected guest memory while in transit we need to
use the SEV commands defined in SEV API spec [1].

SEV guest VMs have the concept of private and shared memory. Private memory
is encrypted with the guest-specific key, while shared memory may be encrypted
with hypervisor key. The commands provided by the SEV FW are meant to be used
for the private memory only. The patch series introduces a new hypercall.
The guest OS can use this hypercall to notify the page encryption status.
If the page is encrypted with guest specific-key then we use SEV command during
the migration. If page is not encrypted then fallback to default.

The patch adds new ioctls KVM_{SET,GET}_PAGE_ENC_BITMAP. The ioctl can be used
by the qemu to get the page encrypted bitmap. Qemu can consult this bitmap
during the migration to know whether the page is encrypted.

[1] https://developer.amd.com/wp-content/resources/55766.PDF

While implementing the migration I stumbled on the follow question:

- Since there is a guest OS changes required to support the migration,
  so how do we know whether guest OS is updated? Should we extend KVM
  capabilities/feature bits to check this?

TODO:
 - reset the bitmap on guest reboot.

The complete tree with patch is available at:
https://github.com/codomania/kvm/tree/sev-migration-rfc-v2

Changes since v1:
 - Add support to share the page encryption between the source and target
   machine.
 - Fix review feedbacks from Tom Lendacky.
 - Add check to limit the session blob length.
 - Update KVM_GET_PAGE_ENC_BITMAP icotl to use the base_gfn instead of
   the memory slot when querying the bitmap.

Brijesh Singh (11):
  KVM: SVM: Add KVM_SEV SEND_START command
  KVM: SVM: Add KVM_SEND_UPDATE_DATA command
  KVM: SVM: Add KVM_SEV_SEND_FINISH command
  KVM: SVM: Add support for KVM_SEV_RECEIVE_START command
  KVM: SVM: Add KVM_SEV_RECEIVE_UPDATE_DATA command
  KVM: SVM: Add KVM_SEV_RECEIVE_FINISH command
  KVM: x86: Add AMD SEV specific Hypercall3
  KVM: X86: Introduce KVM_HC_PAGE_ENC_STATUS hypercall
  KVM: x86: Introduce KVM_GET_PAGE_ENC_BITMAP ioctl
  mm: x86: Invoke hypercall when page encryption status is changed
  KVM: x86: Introduce KVM_SET_PAGE_ENC_BITMAP ioctl

 .../virtual/kvm/amd-memory-encryption.rst     | 120 ++++
 Documentation/virtual/kvm/hypercalls.txt      |  14 +
 arch/x86/include/asm/kvm_host.h               |   4 +
 arch/x86/include/asm/kvm_para.h               |  12 +
 arch/x86/include/asm/mem_encrypt.h            |   3 +
 arch/x86/kvm/svm.c                            | 573 +++++++++++++++++-
 arch/x86/kvm/vmx/vmx.c                        |   1 +
 arch/x86/kvm/x86.c                            |  29 +
 arch/x86/mm/mem_encrypt.c                     |  45 +-
 arch/x86/mm/pageattr.c                        |  15 +
 include/uapi/linux/kvm.h                      |  52 ++
 include/uapi/linux/kvm_para.h                 |   1 +
 12 files changed, 864 insertions(+), 5 deletions(-)