On 03.02.20 17:13, Cornelia Huck wrote: > On Mon, 3 Feb 2020 08:19:49 -0500 > Christian Borntraeger <borntraeger@xxxxxxxxxx> wrote: > >> From: Janosch Frank <frankja@xxxxxxxxxxxxx> >> >> Description of changes that are necessary to move a KVM VM into >> Protected Virtualization mode. > > Maybe move this up to the top of the series, so that new reviewers can > get a quick idea about the architecture as a whole? It might also make Will do. > sense to make the two documents link to each other... I added both files to the kvm index file and changed the title to contain s390. I also added a link to the base doc. > >> >> 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 >> +========================= > > ...especially as the reader will have no idea what a "Protected VM" is, > unless they have read the other document before. > > >> + >> +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. > > s/it/the PVM/ ? ack This section looks now: --- Protected Virtual Machines (PVM) are not accessible by I/O or the hypervisor. When the hypervisor wants to access the memory of PVMs the memory needs to be made accessible. When doing so, the memory will be encrypted. See :doc:`s390-pv` for details. On IPL a.... --- > >> + >> +Based on this data, KVM will make the PV known to the Ultravisor and > > I think the other document uses 'PVM'... probably better to keep that > consistent. The feature name might change to secure execution (SE). I will need to go over this again. But I think we can continue to name the virtual machines protected virtual machines as this is more a description than a brand name. > >> +instruct it to secure its memory, decrypt the components and verify > > Too many it and its here... maybe use the abbreviations instead? fixed > >> +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: > > s/continued/extended/ ? yes. > >> + >> +Subcode 8: Set an IPL Information Block of type 5. > > "type 5" == information block for PVMs? Better spell that out. ack > >> +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 > > s/kernel cmd/kernel command line/ ? ack > >> +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. > > "non-PV guest" == "the guest before it switches to protected > virtualization mode" ? ack > >> + >> + >> +When running in a protected mode some subcodes will result in > > s/in a/in/ ack > >> +exceptions or return error codes. >> + >> +Subcodes 4 and 7 will result in specification exceptions. > > "Subcodes 4 and 7, which would not clear the guest memory, ..." ? Subcodes 4 and 7 will result in specification exceptions as they would not clear out the guest memory. > >> +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. > > In general, this looks like a good overview about how the guest can > move into protected virt mode. > > Some information I'm missing in this doc: Where do the keys come from? > I assume from the machine... is there one key per CEC? Can keys be > transferred? Can an image be introspected to find out if it is possible > to run it on a given system? > > (Not sure if there is a better resting place for that kind of > information.) There will be tooling as part of the s390-tools. I will add --- Keys ---- Every CEC will have a unique public key to enable tooling to build encrypted images. See `s390-tools <https://github.com/ibm-s390-tools/s390-tools/>`_ for the tooling. --- The s390 tools part is not yet upstream but it will be soon.
