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author | Paolo Bonzini <pbonzini@redhat.com> | 2020-03-20 13:34:50 -0400 |
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committer | Paolo Bonzini <pbonzini@redhat.com> | 2020-03-20 13:47:52 -0400 |
commit | 2da1ed62d55c6cbebbdee924f6af4e87bb6666e5 (patch) | |
tree | 6d56bcc69e4cdde9b8ba48197b5f11492f32cc9f /Documentation/virt/kvm | |
parent | d33294541889b023068522270cd4153ddd8e4635 (diff) | |
download | linux-stable-2da1ed62d55c6cbebbdee924f6af4e87bb6666e5.tar.gz linux-stable-2da1ed62d55c6cbebbdee924f6af4e87bb6666e5.tar.bz2 linux-stable-2da1ed62d55c6cbebbdee924f6af4e87bb6666e5.zip |
KVM: SVM: document KVM_MEM_ENCRYPT_OP, let userspace detect if SEV is available
Userspace has no way to query if SEV has been disabled with the
sev module parameter of kvm-amd.ko. Actually it has one, but it
is a hack: do ioctl(KVM_MEM_ENCRYPT_OP, NULL) and check if it
returns EFAULT. Make it a little nicer by returning zero for
SEV enabled and NULL argument, and while at it document the
ioctl arguments.
Cc: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation/virt/kvm')
-rw-r--r-- | Documentation/virt/kvm/amd-memory-encryption.rst | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/Documentation/virt/kvm/amd-memory-encryption.rst b/Documentation/virt/kvm/amd-memory-encryption.rst index d18c97b4e140..c3129b9ba5cb 100644 --- a/Documentation/virt/kvm/amd-memory-encryption.rst +++ b/Documentation/virt/kvm/amd-memory-encryption.rst @@ -53,6 +53,29 @@ key management interface to perform common hypervisor activities such as encrypting bootstrap code, snapshot, migrating and debugging the guest. For more information, see the SEV Key Management spec [api-spec]_ +The main ioctl to access SEV is KVM_MEM_ENCRYPT_OP. If the argument +to KVM_MEM_ENCRYPT_OP is NULL, the ioctl returns 0 if SEV is enabled +and ``ENOTTY` if it is disabled (on some older versions of Linux, +the ioctl runs normally even with a NULL argument, and therefore will +likely return ``EFAULT``). If non-NULL, the argument to KVM_MEM_ENCRYPT_OP +must be a struct kvm_sev_cmd:: + + struct kvm_sev_cmd { + __u32 id; + __u64 data; + __u32 error; + __u32 sev_fd; + }; + + +The ``id`` field contains the subcommand, and the ``data`` field points to +another struct containing arguments specific to command. The ``sev_fd`` +should point to a file descriptor that is opened on the ``/dev/sev`` +device, if needed (see individual commands). + +On output, ``error`` is zero on success, or an error code. Error codes +are defined in ``<linux/psp-dev.h>`. + KVM implements the following commands to support common lifecycle events of SEV guests, such as launching, running, snapshotting, migrating and decommissioning. @@ -90,6 +113,8 @@ Returns: 0 on success, -negative on error On success, the 'handle' field contains a new handle and on error, a negative value. +KVM_SEV_LAUNCH_START requires the ``sev_fd`` field to be valid. + For more details, see SEV spec Section 6.2. 3. KVM_SEV_LAUNCH_UPDATE_DATA |