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Re: [Qemu-devel] [PATCH qemu v7 00/14] spapr: vfio: Enable Dynamic DMA w

From: Alexey Kardashevskiy
Subject: Re: [Qemu-devel] [PATCH qemu v7 00/14] spapr: vfio: Enable Dynamic DMA windows (DDW)
Date: Tue, 05 May 2015 19:30:28 +1000
User-agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0

On 04/25/2015 10:24 PM, Alexey Kardashevskiy wrote:
(cut-n-paste from kernel patchset)

Anyone, ping? :)

Each Partitionable Endpoint (IOMMU group) has an address range on a PCI bus
where devices are allowed to do DMA. These ranges are called DMA windows.
By default, there is a single DMA window, 1 or 2GB big, mapped at zero
on a PCI bus.

PAPR defines a DDW RTAS API which allows pseries guests
querying the hypervisor about DDW support and capabilities (page size mask
for now). A pseries guest may request an additional (to the default)
DMA windows using this RTAS API.
The existing pseries Linux guests request an additional window as big as
the guest RAM and map the entire guest window which effectively creates
direct mapping of the guest memory to a PCI bus.

This patchset reworks PPC64 IOMMU code and adds necessary structures
to support big windows.

Once a Linux guest discovers the presence of DDW, it does:
1. query hypervisor about number of available windows and page size masks;
2. create a window with the biggest possible page size (today 4K/64K/16M);
3. map the entire guest RAM via H_PUT_TCE* hypercalls;
4. switche dma_ops to direct_dma_ops on the selected PE.

Once this is done, H_PUT_TCE is not called anymore for 64bit devices and
the guest does not waste time on DMA map/unmap operations.

Note that 32bit devices won't use DDW and will keep using the default
DMA window so KVM optimizations will be required (to be posted later).

This patchset adds DDW support for pseries. The host kernel changes are
required, posted as:

[PATCH kernel v9 00/32] powerpc/iommu/vfio: Enable Dynamic DMA windows

This patchset is based on git://github.com/dgibson/qemu.git spapr-next branch.
This is also pushed to address@hidden:aik/qemu.git
  + a64ff6f...64ac9a4 64ac9a4 -> vfio-for-github (forced update)

Please comment. Thanks!

* bunch of cleanups, renames after David+Thomas+Michael review
* patches are reorganized and those which do not need the host kernel headers
update are put first and can be pulled if these are good enough :)

* spapr-pci-vfio-host-bridge is now a synonim of spapr-pci-host-bridge -
same PHB can host emulated and VFIO devices
* changed patches order
* lot of small changes

* TCE tables got "enabled" state and are persistent, i.e. not recreated
every reboot
* added v2 of SPAPR_TCE_IOMMU
* fixed migration for emulated PHB with enabled DDW
* huge pile of other changes

* reimplemented the whole thing
* machine reset and ddw-reset RTAS call both remove all TCE tables and
create the default one
* IOMMU group id is not needed to use VFIO PHB anymore, multiple groups
are supported on the same VFIO container and virtual PHB

* removed "reset" from API now
* reworked machine versions
* applied multiple comments
* includes David's machine QOM rework as this patchset adds a new machine type

* tested on emulated PHB
* removed "ddw" machine property, now it is PHB property
* disabled by default
* defined "pseries-2.2" machine which enables DDW by default
* fixed reset() and reference counting

Alexey Kardashevskiy (14):
   spapr_pci: Finish making find_phb()/find_dev() public
   vmstate: Define VARRAY with VMS_ALLOC
   vfio: spapr: Move SPAPR-related code to a separate file
   spapr_pci_vfio: Enable multiple groups per container
   spapr_pci: Convert finish_realize() to
   spapr_iommu: Introduce "enabled" state for TCE table
   spapr_iommu: Add root memory region
   spapr_pci: Do complete reset of DMA config when resetting PHB
   spapr_vfio_pci: Remove redundant spapr-pci-vfio-host-bridge
   linux headers update for DDW on SPAPR
   vfio: spapr: Add SPAPR IOMMU v2 support (DMA memory preregistering)
   spapr: Add pseries-2.4 machine
   spapr_pci/spapr_pci_vfio: Support Dynamic DMA Windows (DDW)
   vfio: Enable DDW ioctls to VFIO IOMMU driver

  hw/ppc/Makefile.objs          |   3 +
  hw/ppc/spapr.c                |  32 ++++-
  hw/ppc/spapr_iommu.c          | 144 +++++++++++++------
  hw/ppc/spapr_pci.c            | 208 ++++++++++++++++++----------
  hw/ppc/spapr_pci_vfio.c       | 147 ++++++++++++--------
  hw/ppc/spapr_rtas_ddw.c       | 300 ++++++++++++++++++++++++++++++++++++++++
  hw/ppc/spapr_vio.c            |   9 +-
  hw/vfio/Makefile.objs         |   1 +
  hw/vfio/common.c              | 180 +++++-------------------
  hw/vfio/spapr.c               | 312 ++++++++++++++++++++++++++++++++++++++++++
  include/hw/pci-host/spapr.h   |  49 +++++--
  include/hw/ppc/spapr.h        |  30 +++-
  include/hw/vfio/vfio-common.h |  16 +++
  include/hw/vfio/vfio.h        |   2 +-
  include/migration/vmstate.h   |  10 ++
  linux-headers/linux/vfio.h    |  88 +++++++++++-
  trace-events                  |   5 +
  17 files changed, 1188 insertions(+), 348 deletions(-)
  create mode 100644 hw/ppc/spapr_rtas_ddw.c
  create mode 100644 hw/vfio/spapr.c


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