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[Xen-devel] [PATCH RFC 00/39] x86/KVM: Xen HVM guest support



Hey,

Presented herewith a series that allows KVM to boot Xen x86 HVM guests (with 
their
respective frontends and backends). On the hypervisor side, the approach is to 
keep
the implementation similar to how HyperV was done on x86 KVM. On the backend 
driver
side, the intent is to reuse Xen support.

Note that this is an RFC so there are bugs and room for improvement. The intent
is to get overall feedback before proceeding further.

Running Xen guests on KVM, enables the following use-cases:

 * Run unmodified Xen HVM images;

 * Facilitate development/testing of Xen guests and Xen PV drivers;

There has been a similar proposal in the past with Xenner, albeit this work
has the following advantages over it:

 * Allows use of existing Xen PV drivers such as block, net etc, both as
 frontends and backends;

 * Xen tooling will see the same UABI as on Xen. This means things like
 xenstored, xenstore-list, xenstore-read run unmodified. Optionally,
 userspace VMM can emulate xenstore operations;

 This work is divided in two parts:

 1. Xen HVM ABI support (patches 1 - 16)

 Support the necessary mechanisms to allow HVM guests to
 boot *without* PV frontends exposed to the guest.
 
 We start by intercepting hypercalls made by the guest, followed
 by event channel IPIs/VIRQs (for PV IPI, timers, spinlocks),
 pvclock and steal clock.

        Ankur Arora (1):
              KVM: x86/xen: support upcall vector

        Boris Ostrovsky (1):
              KVM: x86/xen: handle PV spinlocks slowpath

        Joao Martins (14):
              KVM: x86: fix Xen hypercall page msr handling
              KVM: x86/xen: intercept xen hypercalls if enabled
              KVM: x86/xen: register shared_info page
              KVM: x86/xen: setup pvclock updates
              KVM: x86/xen: update wallclock region
              KVM: x86/xen: register vcpu info
              KVM: x86/xen: register vcpu time info region
              KVM: x86/xen: register steal clock
              KVM: x86: declare Xen HVM guest capability
              KVM: x86/xen: evtchn signaling via eventfd
              KVM: x86/xen: store virq when assigning evtchn
              KVM: x86/xen: handle PV timers oneshot mode
              KVM: x86/xen: handle PV IPI vcpu yield
              KVM: x86: declare Xen HVM evtchn offload capability
         
         Documentation/virtual/kvm/api.txt |   23 ++
         arch/x86/include/asm/kvm_host.h   |   46 ++++
         arch/x86/kvm/Makefile             |    2 +-
         arch/x86/kvm/irq.c                |   25 ++-
         arch/x86/kvm/irq_comm.c           |   11 +
         arch/x86/kvm/trace.h              |   33 +++
         arch/x86/kvm/x86.c                |   60 +++++-
         arch/x86/kvm/x86.h                |    1 +
         arch/x86/kvm/xen.c                | 1025 +++++++++++++++++++++++++++++
         arch/x86/kvm/xen.h                |   48 +++++
         include/linux/kvm_host.h          |   24 +++
         include/uapi/linux/kvm.h          |   73 ++++++-
         12 files changed, 1361 insertions(+), 10 deletions(-)


 2. PV Driver support (patches 17 - 39)

 We start by redirecting hypercalls from the backend to routines
 which emulate the behaviour that PV backends expect i.e. grant
 table and interdomain events. Next, we add support for late
 initialization of xenbus, followed by implementing
 frontend/backend communication mechanisms (i.e. grant tables and
 interdomain event channels). Finally, introduce xen-shim.ko,
 which will setup a limited Xen environment. This uses the added
 functionality of Xen specific shared memory (grant tables) and
 notifications (event channels).

 Note that patch 19 is useful to Xen on its own.

         Ankur Arora (11):
              x86/xen: export vcpu_info and shared_info
              x86/xen: make hypercall_page generic
              KVM: x86/xen: backend hypercall support
              KVM: x86/xen: grant map support
              KVM: x86/xen: grant unmap support
              KVM: x86/xen: interdomain evtchn support
              KVM: x86/xen: evtchn unmask support
              KVM: x86/xen: add additional evtchn ops
              xen-shim: introduce shim domain driver
              xen/gntdev: xen_shim_domain() support
              xen/xenbus: xen_shim_domain() support

        Joao Martins (12):
              xen/xenbus: xenbus uninit support
              xen-blkback: module_exit support
              KVM: x86/xen: domid allocation
              KVM: x86/xen: grant table init
              KVM: x86/xen: grant table grow support
              KVM: x86/xen: grant copy support
              xen/balloon: xen_shim_domain() support
              xen/grant-table: xen_shim_domain() support
              drivers/xen: xen_shim_domain() support
              xen-netback: xen_shim_domain() support
              xen-blkback: xen_shim_domain() support
              KVM: x86: declare Xen HVM Dom0 capability

        [See the entire series diffstat at the end]

There are additional Qemu patches to take advantage of this (and
they are available here[0][1]). An example on how you could run it would be:

$ ./x86_64-softmmu/qemu-system-x86_64 -nodefaults -serial mon:stdio \
  -machine xenfv,accel=kvm \
  -cpu 
host,-kvm,+xen,xen-major-version=4,xen-minor-version=4,+xen-vapic,+xen-pvclock \
  -kernel /path/to/kernel -m 16G -smp 
16,sockets=1,cores=16,threads=1,maxcpus=16 \
  -append "earlyprintk=ttyS0 console=tty0 console=ttyS0" \
  -device xen-platform -device usb-ehci -device usb-tablet,bus=usb-bus.0 -vnc 
:0 -k pt \
  -netdev type=tap,id=net1,ifname=vif1.0,script=qemu-ifup \
  -device xen-nic,netdev=net1,mac=52:54:00:12:34:56,backendtype=vif,backend=0 \
  -drive file=/path/to/image.img,format=raw,id=legacy,if=ide \
  -blockdev file,node-name=drive,filename=/path/to/image.img,locking=off \
  -device xen-disk,vdev=xvda,drive=drive,backendtype=vbd

Naturally other options are still at your disposal (e.g. booting with q35
platform, or with virtio, etc).

Thoughts? 

Cheers,
        Joao

[0] https://www.github.com/jpemartins/qemu xen-shim-rfc
[1] https://www.github.com/jpemartins/linux xen-shim-rfc

 Documentation/virtual/kvm/api.txt        |   33 +
 arch/x86/include/asm/kvm_host.h          |   88 ++
 arch/x86/include/asm/xen/hypercall.h     |   12 +-
 arch/x86/kvm/Kconfig                     |   10 +
 arch/x86/kvm/Makefile                    |    3 +-
 arch/x86/kvm/irq.c                       |   25 +-
 arch/x86/kvm/irq_comm.c                  |   11 +
 arch/x86/kvm/trace.h                     |   33 +
 arch/x86/kvm/x86.c                       |   66 +-
 arch/x86/kvm/x86.h                       |    1 +
 arch/x86/kvm/xen-asm.S                   |   66 +
 arch/x86/kvm/xen-shim.c                  |  138 ++
 arch/x86/kvm/xen.c                       | 2262 ++++++++++++++++++++++++++++++
 arch/x86/kvm/xen.h                       |   55 +
 arch/x86/xen/enlighten.c                 |   49 +
 arch/x86/xen/enlighten_hvm.c             |    3 +-
 arch/x86/xen/enlighten_pv.c              |    1 +
 arch/x86/xen/enlighten_pvh.c             |    3 +-
 arch/x86/xen/xen-asm_32.S                |    2 +-
 arch/x86/xen/xen-asm_64.S                |    2 +-
 arch/x86/xen/xen-head.S                  |    8 +-
 drivers/block/xen-blkback/blkback.c      |   27 +-
 drivers/block/xen-blkback/common.h       |    2 +
 drivers/block/xen-blkback/xenbus.c       |   19 +-
 drivers/net/xen-netback/netback.c        |   25 +-
 drivers/xen/balloon.c                    |   15 +-
 drivers/xen/events/events_2l.c           |    4 +-
 drivers/xen/events/events_base.c         |    6 +-
 drivers/xen/events/events_fifo.c         |    2 +-
 drivers/xen/evtchn.c                     |    4 +-
 drivers/xen/features.c                   |    1 +
 drivers/xen/gntdev.c                     |   10 +-
 drivers/xen/grant-table.c                |   15 +-
 drivers/xen/privcmd.c                    |    5 +-
 drivers/xen/xenbus/xenbus.h              |    2 +
 drivers/xen/xenbus/xenbus_client.c       |   28 +-
 drivers/xen/xenbus/xenbus_dev_backend.c  |    4 +-
 drivers/xen/xenbus/xenbus_dev_frontend.c |    6 +-
 drivers/xen/xenbus/xenbus_probe.c        |   57 +-
 drivers/xen/xenbus/xenbus_xs.c           |   40 +-
 drivers/xen/xenfs/super.c                |    7 +-
 drivers/xen/xenfs/xensyms.c              |    4 +
 include/linux/kvm_host.h                 |   24 +
 include/uapi/linux/kvm.h                 |  104 +-
 include/xen/balloon.h                    |    7 +
 include/xen/xen-ops.h                    |    2 +-
 include/xen/xen.h                        |    5 +
 include/xen/xenbus.h                     |    3 +
 48 files changed, 3232 insertions(+), 67 deletions(-)
 create mode 100644 arch/x86/kvm/xen-asm.S
 create mode 100644 arch/x86/kvm/xen-shim.c
 create mode 100644 arch/x86/kvm/xen.c
 create mode 100644 arch/x86/kvm/xen.h

-- 
2.11.0


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