RE: [PATCH V6 00/24] IOREQ feature (+ virtio-mmio) on Arm

[Wei Chen <Wei.Chen@xxxxxxx>]

Hi Oleksandr,

I just tested the v6 and the latest backend service with the latest staging 
branch.
They work well. 

Tested-by: Wei Chen <Wei.Chen@xxxxxxx>

Cheers,
Wei Chen

> -----Original Message-----
> From: Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>
> Sent: 2021年1月29日 9:48
> To: xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>; Paul Durrant
> <paul@xxxxxxx>; Jan Beulich <jbeulich@xxxxxxxx>; Andrew Cooper
> <andrew.cooper3@xxxxxxxxxx>; Roger Pau Monné <roger.pau@xxxxxxxxxx>;
> Wei Liu <wl@xxxxxxx>; Julien Grall <Julien.Grall@xxxxxxx>; George Dunlap
> <george.dunlap@xxxxxxxxxx>; Ian Jackson <iwj@xxxxxxxxxxxxxx>; Julien Grall
> <julien@xxxxxxx>; Stefano Stabellini <sstabellini@xxxxxxxxxx>; Jun Nakajima
> <jun.nakajima@xxxxxxxxx>; Kevin Tian <kevin.tian@xxxxxxxxx>; Tim Deegan
> <tim@xxxxxxx>; Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>; Volodymyr
> Babchuk <Volodymyr_Babchuk@xxxxxxxx>; Bertrand Marquis
> <Bertrand.Marquis@xxxxxxx>; Wei Chen <Wei.Chen@xxxxxxx>; Kaly Xin
> <Kaly.Xin@xxxxxxx>; Artem Mygaiev <joculator@xxxxxxxxx>; Alex Bennée
> <alex.bennee@xxxxxxxxxx>
> Subject: [PATCH V6 00/24] IOREQ feature (+ virtio-mmio) on Arm
> 
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> 
> 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-V5 series at [2]-[7].
> 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
> and give it a try.
> 
> According to the initial/subsequent discussions there are a few open
> questions/concerns regarding security, performance in VirtIO solution:
> 1. virtio-mmio vs virtio-pci, SPI vs MSI, or even a composition of 
> virtio-mmio +
> 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',
> etc
>    (for these Alex have provided some input at [8])
> 3. interface between toolstack and 'out-of-qemu' virtio backend, avoid using
>    Xenstore in virtio backend if possible. Also, there is a desire to make 
> VirtIO
>    backend hypervisor-agnostic.
> 4. a lot of 'foreing mapping' could lead to the memory exhaustion at the host
> side,
>    as we are stealing the page from host memory in order to map the guest 
> page.
>    Julien has some idea regarding that.
> 5. Julien also has some ideas how to optimize the IOREQ code:
>    5.1 vcpu_ioreq_handle_completion (former handle_hvm_io_completion)
> which is called in
>        an hotpath on Arm (everytime we are re-entering to the guest):
>        Ideally, vcpu_ioreq_handle_completion should be a NOP (at max a few
> instructions)
>        if there is nothing to do (if we don't have I/O forwarded to an IOREQ 
> server).
>        Maybe we want to introduce a per-vCPU flag indicating if an I/O has 
> been
>        forwarded to an IOREQ server. This would allow us to bypass most of the
> function
>        if there is nothing to do.
>    5.2 The current way to handle MMIO is the following:
>        - Pause the vCPU
>        - Forward the access to the backend domain
>        - Schedule the backend domain
>        - Wait for the access to be handled
>        - Unpause the vCPU
>        The sequence is going to be fairly expensive on Xen.
>        It might be possible to optimize the ACK and avoid to wait for the 
> backend
>        to handle the access.
> 
> 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.
> 
> ***
> 
> IMPORTANT NOTES:
> 
> 1. Current patch series doesn't contain VirtIO related changes for the 
> toolstack
> (but they are still available at the GitHub repo [9]):
> - libxl: Introduce basic virtio-mmio support on Arm
> - [RFC] libxl: Add support for virtio-disk configuration
> I decided to skip these patches for now since they require some rework (not 
> Xen
> 4.15 materials),
> I will resume pushing them once we get *common* IOREQ in.
> 
> 2. There are two new patches (according to the recent discussion) which likely
> want Release-Ack:
> - xen/ioreq: Do not let bufioreq to be used on other than x86 arches
> - xen/ioreq: Make the IOREQ feature selectable on Arm
> Also it feels to me that
> - xen/dm: Introduce xendevicemodel_set_irq_level DM op
> doesn't have all required Acks (at least for toolstack part).
> 
> 3. I didn't manage to test patch-by-patch (in all possible modes for x86 and 
> Arm)
> for this version how I did for all previous versions (due to the limited 
> time),
> but I performed selective build-testing for patches touched and with the whole
> series
> applied.
> 
> ***
> 
> 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.
> 
> There are patches on review this series depends on (but it was agreed that 
> this
> series
> could go in without them):
> https://patchwork.kernel.org/patch/11816689
> https://patchwork.kernel.org/patch/11803383
> 
> Please note, that IOREQ feature is disabled by default on Arm within current
> series,
> but there is a possibility to enable it via menuconfig.
> 
> ***
> 
> Patch series [9] was rebased on recent "staging branch"
> (6ca5101 x86/boot: Drop 'noapic' suggestion from check_timer()) and tested on
> Renesas Salvator-X board + H3 ES3.0 SoC (Arm64) with virtio-mmio disk backend
> [10]
> 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://lists.xenproject.org/archives/html/xen-devel/2020-
> 11/msg02188.html
> [6] https://lists.xenproject.org/archives/html/xen-devel/2021-
> 01/msg00749.html
> [7] https://lists.xenproject.org/archives/html/xen-devel/2021-
> 01/msg01899.html
> [8] https://lists.xenproject.org/archives/html/xen-devel/2020-
> 11/msg02212.html
> [9] https://github.com/otyshchenko1/xen/commits/ioreq_4.14_ml7
> [10] https://github.com/otyshchenko1/virtio-disk/commits/ioreq_ml2
> 
> Julien Grall (3):
>   xen/ioreq: Make x86's IOREQ related dm-op handling common
>   xen/mm: Make x86's XENMEM_resource_ioreq_server handling common
>   arm/ioreq: Introduce arch specific bits for IOREQ/DM features
> 
> Oleksandr Tyshchenko (21):
>   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: Call vcpu_ioreq_handle_completion() in check_for_vcpu_work()
>   xen/mm: Handle properly reference in set_foreign_p2m_entry() on Arm
>   xen/ioreq: Introduce domain_has_ioreq_server()
>   xen/dm: Introduce xendevicemodel_set_irq_level DM op
>   xen/arm: io: Abstract sign-extension
>   xen/arm: io: Harden sign extension check
>   xen/ioreq: Make x86's send_invalidate_req() common
>   xen/arm: Add mapcache invalidation handling
>   xen/ioreq: Do not let bufioreq to be used on other than x86 arches
>   xen/ioreq: Make the IOREQ feature selectable on Arm
> 
>  MAINTAINERS                                  |    9 +-
>  tools/include/xendevicemodel.h               |    4 +
>  tools/libs/devicemodel/core.c                |   18 +
>  tools/libs/devicemodel/libxendevicemodel.map |    1 +
>  xen/arch/arm/Makefile                        |    2 +
>  xen/arch/arm/dm.c                            |  149 +++
>  xen/arch/arm/domain.c                        |    9 +
>  xen/arch/arm/io.c                            |   30 +-
>  xen/arch/arm/ioreq.c                         |  196 ++++
>  xen/arch/arm/p2m.c                           |   51 +-
>  xen/arch/arm/traps.c                         |   55 +-
>  xen/arch/x86/Kconfig                         |    2 +-
>  xen/arch/x86/hvm/dm.c                        |  134 +--
>  xen/arch/x86/hvm/emulate.c                   |  220 ++--
>  xen/arch/x86/hvm/hvm.c                       |   14 +-
>  xen/arch/x86/hvm/hypercall.c                 |    9 +-
>  xen/arch/x86/hvm/intercept.c                 |    5 +-
>  xen/arch/x86/hvm/io.c                        |   52 +-
>  xen/arch/x86/hvm/ioreq.c                     | 1368 ++----------------------
>  xen/arch/x86/hvm/stdvga.c                    |   12 +-
>  xen/arch/x86/hvm/svm/nestedsvm.c             |    2 +-
>  xen/arch/x86/hvm/vmx/realmode.c              |    8 +-
>  xen/arch/x86/hvm/vmx/vvmx.c                  |    5 +-
>  xen/arch/x86/mm.c                            |   46 +-
>  xen/arch/x86/mm/p2m-ept.c                    |    1 +
>  xen/arch/x86/mm/p2m-pt.c                     |    1 +
>  xen/arch/x86/mm/p2m.c                        |   17 +-
>  xen/arch/x86/mm/shadow/common.c              |    2 +-
>  xen/common/Kconfig                           |   12 +-
>  xen/common/Makefile                          |    2 +
>  xen/common/dm.c                              |   55 +
>  xen/common/ioreq.c                           | 1429 
> ++++++++++++++++++++++++++
>  xen/common/memory.c                          |   72 +-
>  xen/include/asm-arm/domain.h                 |    2 +
>  xen/include/asm-arm/ioreq.h                  |   70 ++
>  xen/include/asm-arm/mmio.h                   |    1 +
>  xen/include/asm-arm/p2m.h                    |   19 +-
>  xen/include/asm-arm/traps.h                  |   25 +
>  xen/include/asm-x86/hvm/domain.h             |   45 -
>  xen/include/asm-x86/hvm/emulate.h            |    2 +-
>  xen/include/asm-x86/hvm/io.h                 |   17 -
>  xen/include/asm-x86/hvm/ioreq.h              |   39 +-
>  xen/include/asm-x86/hvm/vcpu.h               |   18 -
>  xen/include/asm-x86/ioreq.h                  |   39 +
>  xen/include/asm-x86/mm.h                     |    4 -
>  xen/include/asm-x86/p2m.h                    |   22 +-
>  xen/include/public/hvm/dm_op.h               |   16 +
>  xen/include/xen/dm.h                         |   44 +
>  xen/include/xen/ioreq.h                      |  140 +++
>  xen/include/xen/mm.h                         |    9 -
>  xen/include/xen/p2m-common.h                 |    4 +
>  xen/include/xen/sched.h                      |   34 +
>  xen/include/xsm/dummy.h                      |    4 +-
>  xen/include/xsm/xsm.h                        |    6 +-
>  xen/xsm/dummy.c                              |    2 +-
>  xen/xsm/flask/hooks.c                        |    5 +-
>  56 files changed, 2722 insertions(+), 1837 deletions(-)
>  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/ioreq.h
>  create mode 100644 xen/include/asm-x86/ioreq.h
>  create mode 100644 xen/include/xen/dm.h
>  create mode 100644 xen/include/xen/ioreq.h
> 
> --
> 2.7.4