From: Janosch Frank <frankja@xxxxxxxxxxxxx> Description of changes that are necessary to move a KVM VM into Protected Virtualization mode. Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx> --- Documentation/virt/kvm/s390-pv-boot.rst | 64 +++++++++++++++++++++++++ 1 file changed, 64 insertions(+) create mode 100644 Documentation/virt/kvm/s390-pv-boot.rst diff --git a/Documentation/virt/kvm/s390-pv-boot.rst b/Documentation/virt/kvm/s390-pv-boot.rst new file mode 100644 index 000000000000..431cd5d7f686 --- /dev/null +++ b/Documentation/virt/kvm/s390-pv-boot.rst @@ -0,0 +1,64 @@ +.. SPDX-License-Identifier: GPL-2.0 +========================= +Boot/IPL of Protected VMs +========================= + +Summary +------- +Protected VMs are encrypted while not running. On IPL a small +plaintext bootloader is started which provides information about the +encrypted components and necessary metadata to KVM to decrypt it. + +Based on this data, KVM will make the PV known to the Ultravisor and +instruct it to secure its memory, decrypt the components and verify +the data and address list hashes, to ensure integrity. Afterwards KVM +can run the PV via SIE which the UV will intercept and execute on +KVM's behalf. + +The switch into PV mode lets us load encrypted guest executables and +data via every available method (network, dasd, scsi, direct kernel, +...) without the need to change the boot process. + + +Diag308 +------- +This diagnose instruction is the basis for VM IPL. The VM can set and +retrieve IPL information blocks, that specify the IPL method/devices +and request VM memory and subsystem resets, as well as IPLs. + +For PVs this concept has been continued with new subcodes: + +Subcode 8: Set an IPL Information Block of type 5. +Subcode 9: Store the saved block in guest memory +Subcode 10: Move into Protected Virtualization mode + +The new PV load-device-specific-parameters field specifies all data, +that is necessary to move into PV mode. + +* PV Header origin +* PV Header length +* List of Components composed of + * AES-XTS Tweak prefix + * Origin + * Size + +The PV header contains the keys and hashes, which the UV will use to +decrypt and verify the PV, as well as control flags and a start PSW. + +The components are for instance an encrypted kernel, kernel cmd and +initrd. The components are decrypted by the UV. + +All non-decrypted data of the non-PV guest instance are zero on first +access of the PV. + + +When running in a protected mode some subcodes will result in +exceptions or return error codes. + +Subcodes 4 and 7 will result in specification exceptions. +When removing a secure VM, the UV will clear all memory, so we can't +have non-clearing IPL subcodes. + +Subcodes 8, 9, 10 will result in specification exceptions. +Re-IPL into a protected mode is only possible via a detour into non +protected mode. -- 2.24.0
