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 sense to make the two documents link to each other... > > 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/ ? > + > +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. > +instruct it to secure its memory, decrypt the components and verify Too many it and its here... maybe use the abbreviations instead? > +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/ ? > + > +Subcode 8: Set an IPL Information Block of type 5. "type 5" == information block for PVMs? Better spell that out. > +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/ ? > +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" ? > + > + > +When running in a protected mode some subcodes will result in s/in a/in/ > +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, ..." ? > +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.)
