Merge remote-tracking branch 'remotes/cohuck/tags/s390x-20200430' into staging

- update Linux headers to 5.7-rc3 (and virtio-net fixup)
- support for protected virtualization aka secure execution

# gpg: Signature made Thu 30 Apr 2020 10:41:31 BST
# gpg:                using RSA key C3D0D66DC3624FF6A8C018CEDECF6B93C6F02FAF
# gpg:                issuer "cohuck@redhat.com"
# gpg: Good signature from "Cornelia Huck <conny@cornelia-huck.de>" [marginal]
# gpg:                 aka "Cornelia Huck <huckc@linux.vnet.ibm.com>" [full]
# gpg:                 aka "Cornelia Huck <cornelia.huck@de.ibm.com>" [full]
# gpg:                 aka "Cornelia Huck <cohuck@kernel.org>" [marginal]
# gpg:                 aka "Cornelia Huck <cohuck@redhat.com>" [marginal]
# Primary key fingerprint: C3D0 D66D C362 4FF6 A8C0  18CE DECF 6B93 C6F0 2FAF

* remotes/cohuck/tags/s390x-20200430:
  s390x/s390-virtio-ccw: Fix build on systems without KVM
  s390x/pv: Retry ioctls on -EINTR
  s390x: protvirt: Fix stray error_report_err in s390_machine_protect
  s390x: Add unpack facility feature to GA1
  docs: system: Add protvirt docs
  s390x: protvirt: Handle SIGP store status correctly
  s390x: protvirt: Move IO control structures over SIDA
  s390x: protvirt: Disable address checks for PV guest IO emulation
  s390x: protvirt: Move diag 308 data over SIDA
  s390x: protvirt: Set guest IPL PSW
  s390x: protvirt: SCLP interpretation
  s390x: protvirt: Move STSI data over SIDAD
  s390x: Add SIDA memory ops
  s390x: protvirt: KVM intercept changes
  s390x: protvirt: Inhibit balloon when switching to protected mode
  s390x: protvirt: Add migration blocker
  s390x: protvirt: Support unpack facility
  s390x: Move diagnose 308 subcodes and rcs into ipl.h
  linux-headers: update against Linux 5.7-rc3
  virtio-net: fix rsc_ext compat handling

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 60 insertions, 0 deletions

diff --git a/docs/system/s390x/protvirt.rst b/docs/system/s390x/protvirt.rst
new file mode 100644
index 0000000000..712974ad87
--- /dev/null
+++ b/docs/system/s390x/protvirt.rst
@@ -0,0 +1,60 @@
+Protected Virtualization on s390x
+=================================
+
+The memory and most of the registers of Protected Virtual Machines
+(PVMs) are encrypted or inaccessible to the hypervisor, effectively
+prohibiting VM introspection when the VM is running. At rest, PVMs are
+encrypted and can only be decrypted by the firmware, represented by an
+entity called Ultravisor, of specific IBM Z machines.
+
+
+Prerequisites
+-------------
+
+To run PVMs, a machine with the Protected Virtualization feature, as
+indicated by the Ultravisor Call facility (stfle bit 158), is
+required. The Ultravisor needs to be initialized at boot by setting
+`prot_virt=1` on the host's kernel command line.
+
+Running PVMs requires using the KVM hypervisor.
+
+If those requirements are met, the capability `KVM_CAP_S390_PROTECTED`
+will indicate that KVM can support PVMs on that LPAR.
+
+
+QEMU Settings
+-------------
+
+To indicate to the VM that it can transition into protected mode, the
+`Unpack facility` (stfle bit 161 represented by the feature
+`unpack`/`S390_FEAT_UNPACK`) needs to be part of the cpu model of
+the VM.
+
+All I/O devices need to use the IOMMU.
+Passthrough (vfio) devices are currently not supported.
+
+Host huge page backings are not supported. However guests can use huge
+pages as indicated by its facilities.
+
+
+Boot Process
+------------
+
+A secure guest image can either be loaded from disk or supplied on the
+QEMU command line. Booting from disk is done by the unmodified
+s390-ccw BIOS. I.e., the bootmap is interpreted, multiple components
+are read into memory and control is transferred to one of the
+components (zipl stage3). Stage3 does some fixups and then transfers
+control to some program residing in guest memory, which is normally
+the OS kernel. The secure image has another component prepended
+(stage3a) that uses the new diag308 subcodes 8 and 10 to trigger the
+transition into secure mode.
+
+Booting from the image supplied on the QEMU command line requires that
+the file passed via -kernel has the same memory layout as would result
+from the disk boot. This memory layout includes the encrypted
+components (kernel, initrd, cmdline), the stage3a loader and
+metadata. In case this boot method is used, the command line
+options -initrd and -cmdline are ineffective. The preparation of a PVM
+image is done via the `genprotimg` tool from the s390-tools
+collection.