Re: [PATCH v5 0/8] s390: virtio: support protected virtualization

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Halil,

I just ran my toleration tests successfully on current HW for
this series.

Michael

On 12.06.19 13:12, Halil Pasic wrote:
Enhanced virtualization protection technology may require the use of
bounce buffers for I/O. While support for this was built into the virtio
core, virtio-ccw wasn't changed accordingly.

Some background on technology (not part of this series) and the
terminology used.

* Protected Virtualization (PV):

Protected Virtualization guarantees, that non-shared memory of a  guest
that operates in PV mode private to that guest. I.e. any attempts by the
hypervisor or other guests to access it will result in an exception. If
supported by the environment (machine, KVM, guest VM) a guest can decide
to change into PV mode by doing the appropriate ultravisor calls.

* Ultravisor:

A hardware/firmware entity that manages PV guests, and polices access to
their memory. A PV guest prospect needs to interact with the ultravisor,
to enter PV mode, and potentially to share pages (for I/O which should
be encrypted by the guest). A guest interacts with the ultravisor via so
called ultravisor calls. A hypervisor needs to interact with the
ultravisor to facilitate interpretation, emulation and swapping. A
hypervisor  interacts with the ultravisor via ultravisor calls and via
the SIE state description. Generally the ultravisor sanitizes hypervisor
inputs so that the guest can not be corrupted (except for denial of
service.


What needs to be done
=====================

Thus what needs to be done to bring virtio-ccw up to speed with respect
to protected virtualization is:
* use some 'new' common virtio stuff
* make sure that virtio-ccw specific stuff uses shared memory when
   talking to the hypervisor (except control/communication blocks like ORB,
   these are handled by the ultravisor)
* make sure the DMA API does what is necessary to talk through shared
   memory if we are a protected virtualization guest.
* make sure the common IO layer plays along as well (airqs, sense).


Important notes
================

* This patch set is based on Martins features branch
  (git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux.git branch
  'features').

* Documentation is still very sketchy. I'm committed to improving this,
   but I'm currently hampered by some dependencies currently.

* The existing naming in the common infrastructure (kernel internal
   interfaces) is pretty much based on the AMD SEV terminology. Thus the
   names aren't always perfect. There might be merit to changing these
   names to more abstract ones. I did not put much thought into that at
   the current stage.

* Testing: Please use iommu_platform=on for any virtio devices you are
   going to test this code with (so virtio actually uses the DMA API).

@Sebastian: I kept your r-b on patch 2 "s390/cio: introduce DMA pools to
cio" despite the small changes pointed out below. Please do complain if
it ain't OK for you!

Change log
==========

v4 --> v5:
* work around dma_pool API not tolerating NULL dma pool (patch 4)
* make the genpool based dma pools API  tolerate NULL genpool (patch 2)
* fix typo (patch 2)
* fix unintended code move (patch 7)
* add more r-b's



v3 --> v4
* fixed cleanup in css_bus_init() (Connie)
* made cio.h include genalloc.h instead of a forward declaration
   (Connie)
* added comments about dma_mask/coherent_dma_mask values (Connie)
* fixed error handling in virtio_ccw_init() (Connie)
* got rid of the *vc_dma* wrappers (Connie)
* added some Reviewed-bys
* rebased on top of current master, no changes were necessary

v2 --> v3:
* patch 2/8
     potential cio_dma_pool_init() returning NULL issue fixed
     potential cio_gp_dma_create() returning NULL issue fixed
     warning issues with doc type comments fixed
     unused define statement removed
* patch 3/8
     potential cio_gp_dma_create() returning NULL issue fixed
     whitespace issue fixed
     warning issues with doc type comments fixed
* patch 8/8
     potential cio_dma_zalloc() returning NULL issue fixed

v1 --> v2:
* patch "virtio/s390: use vring_create_virtqueue" went already upstream
* patch "virtio/s390: DMA support for virtio-ccw" went already upstream
* patch "virtio/s390: enable packed ring" went already upstream
* Made dev.dma_mask point to dev.coherent_dma_mask for css, subchannel
   and ccw devices.
* While rebasing 's390/airq: use DMA memory for adapter interrupts' the
   newly introduced kmem_cache  was replaced with an equivalent dma_pool;
   the kalloc() allocations are now replaced with cio_dma_zalloc()
   allocations to avoid wasting almost a full page.
* Made virtio-ccw use the new AIRQ_IV_CACHELINE flag.
* fixed all remaining checkpatch issues

RFC --> v1:
* Fixed bugs found by Connie (may_reduce and handling reduced,  warning,
   split move -- thanks Connie!).
* Fixed console bug found by Sebastian (thanks Sebastian!).
* Removed the completely useless duplicate of dma-mapping.h spotted by
   Christoph (thanks Christoph!).
* Don't use the global DMA pool for subchannel and ccw device
   owned memory as requested by Sebastian. Consequences:
	* Both subchannel and ccw devices have their dma masks
	now (both specifying 31 bit addressable)
	* We require at least 2 DMA pages per ccw device now, most of
	this memory is wasted though.
	* DMA memory allocated by virtio is also 31 bit addressable now
         as virtio uses the parent (which is the ccw device).
* Enabled packed ring.
* Rebased onto Martins feature branch; using the actual uv (ultravisor)
   interface instead of TODO comments.
* Added some explanations to the cover letter (Connie, David).
* Squashed a couple of patches together and fixed some text stuff.

Halil Pasic (8):
   s390/mm: force swiotlb for protected virtualization
   s390/cio: introduce DMA pools to cio
   s390/cio: add basic protected virtualization support
   s390/airq: use DMA memory for adapter interrupts
   virtio/s390: use cacheline aligned airq bit vectors
   virtio/s390: add indirection to indicators access
   virtio/s390: use DMA memory for ccw I/O and classic notifiers
   virtio/s390: make airq summary indicators DMA

  arch/s390/Kconfig                   |   5 +
  arch/s390/include/asm/airq.h        |   2 +
  arch/s390/include/asm/ccwdev.h      |   4 +
  arch/s390/include/asm/cio.h         |  11 ++
  arch/s390/include/asm/mem_encrypt.h |  18 ++
  arch/s390/mm/init.c                 |  47 ++++++
  drivers/s390/cio/airq.c             |  37 +++--
  drivers/s390/cio/ccwreq.c           |   9 +-
  drivers/s390/cio/cio.h              |   2 +
  drivers/s390/cio/css.c              | 134 ++++++++++++++-
  drivers/s390/cio/device.c           |  68 ++++++--
  drivers/s390/cio/device_fsm.c       |  49 +++---
  drivers/s390/cio/device_id.c        |  20 ++-
  drivers/s390/cio/device_ops.c       |  21 ++-
  drivers/s390/cio/device_pgid.c      |  22 +--
  drivers/s390/cio/device_status.c    |  24 +--
  drivers/s390/cio/io_sch.h           |  20 ++-
  drivers/s390/virtio/virtio_ccw.c    | 246 +++++++++++++++-------------
  18 files changed, 538 insertions(+), 201 deletions(-)
  create mode 100644 arch/s390/include/asm/mem_encrypt.h


--
Mit freundlichen Grüßen / Kind regards
Michael Müller

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