Re: [RFC 30/37] DOCUMENTATION: protvirt: Diag 308 IPL

[Cornelia Huck <cohuck@redhat.com>]

On Thu, 24 Oct 2019 07:40:52 -0400
Janosch Frank <frankja@linux.ibm.com> wrote:

> Description of changes that are necessary to move a KVM VM into
> Protected Virtualization mode.
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> ---
>  Documentation/virtual/kvm/s390-pv-boot.txt | 62 ++++++++++++++++++++++
>  1 file changed, 62 insertions(+)
>  create mode 100644 Documentation/virtual/kvm/s390-pv-boot.txt
> 
> diff --git a/Documentation/virtual/kvm/s390-pv-boot.txt b/Documentation/virtual/kvm/s390-pv-boot.txt
> new file mode 100644
> index 000000000000..af883c928c08
> --- /dev/null
> +++ b/Documentation/virtual/kvm/s390-pv-boot.txt
> @@ -0,0 +1,62 @@
> +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 vor VM IPL. The VM can set and

s/vor/for/

> +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.

So... what do we IPL from? Is there still a need for the bios?

(Sorry, I'm a bit confused here.)