Re: [PATCH V3 00/23] IOREQ feature (+ virtio-mmio) on Arm

[Oleksandr <olekstysh@gmail.com>]

On 30.11.20 12:31, Oleksandr Tyshchenko wrote:
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

Hello all.

Added missed subject line. I am sorry for the inconvenience.


>
>
> Date: Sat, 28 Nov 2020 22:33:51 +0200
> Subject: [PATCH V3 00/23] IOREQ feature (+ virtio-mmio) on Arm
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>
> Hello all.
>
> The purpose of this patch series is to add IOREQ/DM support to Xen on Arm.
> You can find an initial discussion at [1] and RFC/V1/V2 series at [2]/[3]/[4].
> Xen on Arm requires some implementation to forward guest MMIO access to a device
> model in order to implement virtio-mmio backend or even mediator outside of hypervisor.
> As Xen on x86 already contains required support this series tries to make it common
> and introduce Arm specific bits plus some new functionality. Patch series is based on
> Julien's PoC "xen/arm: Add support for Guest IO forwarding to a device emulator".
> Besides splitting existing IOREQ/DM support and introducing Arm side, the series
> also includes virtio-mmio related changes (last 2 patches for toolstack)
> for the reviewers to be able to see how the whole picture could look like.
>
> According to the initial discussion there are a few open questions/concerns
> regarding security, performance in VirtIO solution:
> 1. virtio-mmio vs virtio-pci, SPI vs MSI, different use-cases require different
>     transport...
> 2. virtio backend is able to access all guest memory, some kind of protection
>     is needed: 'virtio-iommu in Xen' vs 'pre-shared-memory & memcpys in guest'
> 3. interface between toolstack and 'out-of-qemu' virtio backend, avoid using
>     Xenstore in virtio backend if possible.
> 4. a lot of 'foreing mapping' could lead to the memory exhaustion, Julien
>     has some idea regarding that.
>
> Looks like all of them are valid and worth considering, but the first thing
> which we need on Arm is a mechanism to forward guest IO to a device emulator,
> so let's focus on it in the first place.
>
> ***
>
> There are a lot of changes since RFC series, almost all TODOs were resolved on Arm,
> Arm code was improved and hardened, common IOREQ/DM code became really arch-agnostic
> (without HVM-ism), the "legacy" mechanism of mapping magic pages for the IOREQ servers
> was left x86 specific, etc. But one TODO still remains which is "PIO handling" on Arm.
> The "PIO handling" TODO is expected to left unaddressed for the current series.
> It is not an big issue for now while Xen doesn't have support for vPCI on Arm.
> On Arm64 they are only used for PCI IO Bar and we would probably want to expose
> them to emulator as PIO access to make a DM completely arch-agnostic. So "PIO handling"
> should be implemented when we add support for vPCI.
>
> I left interface untouched in the following patch
> "xen/dm: Introduce xendevicemodel_set_irq_level DM op"
> since there is still an open discussion what interface to use/what
> information to pass to the hypervisor.
>
> There is a patch on review this series depends on:
> https://patchwork.kernel.org/patch/11816689
>
> Please note, that IOREQ feature is disabled by default on Arm within current series.
>
> ***
>
> Patch series [5] was rebased on recent "staging branch"
> (181f2c2 evtchn: double per-channel locking can't hit identical channels) and tested on
> Renesas Salvator-X board + H3 ES3.0 SoC (Arm64) with virtio-mmio disk backend [6]
> running in driver domain and unmodified Linux Guest running on existing
> virtio-blk driver (frontend). No issues were observed. Guest domain 'reboot/destroy'
> use-cases work properly. Patch series was only build-tested on x86.
>
> Please note, build-test passed for the following modes:
> 1. x86: CONFIG_HVM=y / CONFIG_IOREQ_SERVER=y (default)
> 2. x86: #CONFIG_HVM is not set / #CONFIG_IOREQ_SERVER is not set
> 3. Arm64: CONFIG_HVM=y / CONFIG_IOREQ_SERVER=y
> 4. Arm64: CONFIG_HVM=y / #CONFIG_IOREQ_SERVER is not set  (default)
> 5. Arm32: CONFIG_HVM=y / CONFIG_IOREQ_SERVER=y
> 6. Arm32: CONFIG_HVM=y / #CONFIG_IOREQ_SERVER is not set  (default)
>
> ***
>
> Any feedback/help would be highly appreciated.
>
> [1] https://lists.xenproject.org/archives/html/xen-devel/2020-07/msg00825.html
> [2] https://lists.xenproject.org/archives/html/xen-devel/2020-08/msg00071.html
> [3] https://lists.xenproject.org/archives/html/xen-devel/2020-09/msg00732.html
> [4] https://lists.xenproject.org/archives/html/xen-devel/2020-10/msg01077.html
> [5] https://github.com/otyshchenko1/xen/commits/ioreq_4.14_ml4
> [6] https://github.com/xen-troops/virtio-disk/commits/ioreq_ml1
>
> Julien Grall (5):
>    xen/dm: Make x86's DM feature common
>    xen/mm: Make x86's XENMEM_resource_ioreq_server handling common
>    arm/ioreq: Introduce arch specific bits for IOREQ/DM features
>    xen/dm: Introduce xendevicemodel_set_irq_level DM op
>    libxl: Introduce basic virtio-mmio support on Arm
>
> Oleksandr Tyshchenko (18):
>    x86/ioreq: Prepare IOREQ feature for making it common
>    x86/ioreq: Add IOREQ_STATUS_* #define-s and update code for moving
>    x86/ioreq: Provide out-of-line wrapper for the handle_mmio()
>    xen/ioreq: Make x86's IOREQ feature common
>    xen/ioreq: Make x86's hvm_ioreq_needs_completion() common
>    xen/ioreq: Make x86's hvm_mmio_first(last)_byte() common
>    xen/ioreq: Make x86's hvm_ioreq_(page/vcpu/server) structs common
>    xen/ioreq: Move x86's ioreq_server to struct domain
>    xen/ioreq: Move x86's io_completion/io_req fields to struct vcpu
>    xen/ioreq: Remove "hvm" prefixes from involved function names
>    xen/ioreq: Use guest_cmpxchg64() instead of cmpxchg()
>    xen/arm: Stick around in leave_hypervisor_to_guest until I/O has
>      completed
>    xen/mm: Handle properly reference in set_foreign_p2m_entry() on Arm
>    xen/ioreq: Introduce domain_has_ioreq_server()
>    xen/arm: io: Abstract sign-extension
>    xen/ioreq: Make x86's send_invalidate_req() common
>    xen/arm: Add mapcache invalidation handling
>    [RFC] libxl: Add support for virtio-disk configuration
>
>   MAINTAINERS                                  |    8 +-
>   tools/include/xendevicemodel.h               |    4 +
>   tools/libs/devicemodel/core.c                |   18 +
>   tools/libs/devicemodel/libxendevicemodel.map |    1 +
>   tools/libs/light/Makefile                    |    1 +
>   tools/libs/light/libxl_arm.c                 |   94 +-
>   tools/libs/light/libxl_create.c              |    1 +
>   tools/libs/light/libxl_internal.h            |    1 +
>   tools/libs/light/libxl_types.idl             |   16 +
>   tools/libs/light/libxl_types_internal.idl    |    1 +
>   tools/libs/light/libxl_virtio_disk.c         |  109 +++
>   tools/xl/Makefile                            |    2 +-
>   tools/xl/xl.h                                |    3 +
>   tools/xl/xl_cmdtable.c                       |   15 +
>   tools/xl/xl_parse.c                          |  116 +++
>   tools/xl/xl_virtio_disk.c                    |   46 +
>   xen/arch/arm/Makefile                        |    2 +
>   xen/arch/arm/dm.c                            |   89 ++
>   xen/arch/arm/domain.c                        |    9 +
>   xen/arch/arm/hvm.c                           |    4 +
>   xen/arch/arm/io.c                            |   29 +-
>   xen/arch/arm/ioreq.c                         |  126 +++
>   xen/arch/arm/p2m.c                           |   48 +-
>   xen/arch/arm/traps.c                         |   58 +-
>   xen/arch/x86/Kconfig                         |    1 +
>   xen/arch/x86/hvm/dm.c                        |  295 +-----
>   xen/arch/x86/hvm/emulate.c                   |   80 +-
>   xen/arch/x86/hvm/hvm.c                       |   12 +-
>   xen/arch/x86/hvm/hypercall.c                 |    9 +-
>   xen/arch/x86/hvm/intercept.c                 |    5 +-
>   xen/arch/x86/hvm/io.c                        |   26 +-
>   xen/arch/x86/hvm/ioreq.c                     | 1357 ++------------------------
>   xen/arch/x86/hvm/stdvga.c                    |   10 +-
>   xen/arch/x86/hvm/svm/nestedsvm.c             |    2 +-
>   xen/arch/x86/hvm/vmx/realmode.c              |    6 +-
>   xen/arch/x86/hvm/vmx/vvmx.c                  |    2 +-
>   xen/arch/x86/mm.c                            |   46 +-
>   xen/arch/x86/mm/p2m.c                        |   13 +-
>   xen/arch/x86/mm/shadow/common.c              |    2 +-
>   xen/common/Kconfig                           |    3 +
>   xen/common/Makefile                          |    2 +
>   xen/common/dm.c                              |  292 ++++++
>   xen/common/ioreq.c                           | 1307 +++++++++++++++++++++++++
>   xen/common/memory.c                          |   73 +-
>   xen/include/asm-arm/domain.h                 |    3 +
>   xen/include/asm-arm/hvm/ioreq.h              |  139 +++
>   xen/include/asm-arm/mm.h                     |    8 -
>   xen/include/asm-arm/mmio.h                   |    1 +
>   xen/include/asm-arm/p2m.h                    |   19 +-
>   xen/include/asm-arm/traps.h                  |   24 +
>   xen/include/asm-x86/hvm/domain.h             |   43 -
>   xen/include/asm-x86/hvm/emulate.h            |    2 +-
>   xen/include/asm-x86/hvm/io.h                 |   17 -
>   xen/include/asm-x86/hvm/ioreq.h              |   58 +-
>   xen/include/asm-x86/hvm/vcpu.h               |   18 -
>   xen/include/asm-x86/mm.h                     |    4 -
>   xen/include/asm-x86/p2m.h                    |   24 +-
>   xen/include/public/arch-arm.h                |    5 +
>   xen/include/public/hvm/dm_op.h               |   16 +
>   xen/include/xen/dm.h                         |   44 +
>   xen/include/xen/ioreq.h                      |  146 +++
>   xen/include/xen/p2m-common.h                 |    4 +
>   xen/include/xen/sched.h                      |   32 +
>   xen/include/xsm/dummy.h                      |    4 +-
>   xen/include/xsm/xsm.h                        |    6 +-
>   xen/xsm/dummy.c                              |    2 +-
>   xen/xsm/flask/hooks.c                        |    5 +-
>   67 files changed, 3084 insertions(+), 1884 deletions(-)
>   create mode 100644 tools/libs/light/libxl_virtio_disk.c
>   create mode 100644 tools/xl/xl_virtio_disk.c
>   create mode 100644 xen/arch/arm/dm.c
>   create mode 100644 xen/arch/arm/ioreq.c
>   create mode 100644 xen/common/dm.c
>   create mode 100644 xen/common/ioreq.c
>   create mode 100644 xen/include/asm-arm/hvm/ioreq.h
>   create mode 100644 xen/include/xen/dm.h
>   create mode 100644 xen/include/xen/ioreq.h
>
-- 
Regards,

Oleksandr Tyshchenko