Re: [PATCH V4 00/24] IOREQ feature (+ virtio-mmio) on Arm

[Oleksandr <olekstysh@gmail.com>]

On 14.01.21 05:55, Wei Chen wrote:
> Hi Oleksandr,

Hi Wei.


>
> I have tested this series with latest master and staging branches.
> The virtio function works well for Arm as v3.

Thank you! This is good news.


>
> For latest staging branch, it needs a tiny rebase for:
> 0011 xen/mm: Make x86's XENMEM_resource_ioreq_server handling common
> As staging branch changes rapidly, I had done it manually and done the test.
> It should not affect review.

Yes, very rapidly I would say) Yes, I will need to rebase due to the 
recent "xen/memory: Introduce CONFIG_ARCH_ACQUIRE_RESOURCE" patch


>
> Tested-by: Wei Chen <Wei.Chen@arm.com>

Thanks.


>
>> -----Original Message-----
>> From: Xen-devel <xen-devel-bounces@lists.xenproject.org> On Behalf Of
>> Oleksandr Tyshchenko
>> Sent: 2021年1月13日 5:52
>> To: xen-devel@lists.xenproject.org
>> Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>; Paul Durrant
>> <paul@xen.org>; Jan Beulich <jbeulich@suse.com>; Andrew Cooper
>> <andrew.cooper3@citrix.com>; Roger Pau Monné <roger.pau@citrix.com>;
>> Wei Liu <wl@xen.org>; Julien Grall <Julien.Grall@arm.com>; George Dunlap
>> <george.dunlap@citrix.com>; Ian Jackson <iwj@xenproject.org>; Julien Grall
>> <julien@xen.org>; Stefano Stabellini <sstabellini@kernel.org>; Jun Nakajima
>> <jun.nakajima@intel.com>; Kevin Tian <kevin.tian@intel.com>; Tim Deegan
>> <tim@xen.org>; Daniel De Graaf <dgdegra@tycho.nsa.gov>; Volodymyr
>> Babchuk <Volodymyr_Babchuk@epam.com>; Anthony PERARD
>> <anthony.perard@citrix.com>; Bertrand Marquis <Bertrand.Marquis@arm.com>;
>> Wei Chen <Wei.Chen@arm.com>; Kaly Xin <Kaly.Xin@arm.com>; Artem
>> Mygaiev <joculator@gmail.com>; Alex Bennée <alex.bennee@linaro.org>
>> Subject: [PATCH V4 00/24] IOREQ feature (+ virtio-mmio) on Arm
>>
>> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
>>
>> 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-V3 series at [2]-[5].
>> 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 the first two Alex have provided valuable input at [6])
>> 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.
>>
>> ***
>>
>> 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. Also patch that makes DM code public was reworked
>> to have
>> the top level dm-op handling arch-specific and call into ioreq_server_dm_op()
>> for otherwise unhandled ops.
>> 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 are patches on review this series depends on:
>> 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.
>>
>> ***
>>
>> Patch series [7] was rebased on recent "staging branch"
>> (7ba2ab4 x86/p2m: Fix paging_gva_to_gfn() for nested virt) and tested on
>> Renesas Salvator-X board + H3 ES3.0 SoC (Arm64) with virtio-mmio disk backend
>> [8]
>> 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/2020-
>> 11/msg02212.html
>> [7] https://github.com/otyshchenko1/xen/commits/ioreq_4.14_ml5
>> [8] https://github.com/xen-troops/virtio-disk/commits/ioreq_ml1
>>
>> Julien Grall (5):
>>    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
>>    xen/dm: Introduce xendevicemodel_set_irq_level DM op
>>    libxl: Introduce basic virtio-mmio support on Arm
>>
>> Oleksandr Tyshchenko (19):
>>    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/arm: io: Harden sign extension check
>>    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                            |  174 ++++
>>   xen/arch/arm/domain.c                        |    9 +
>>   xen/arch/arm/io.c                            |   30 +-
>>   xen/arch/arm/ioreq.c                         |  198 ++++
>>   xen/arch/arm/p2m.c                           |   51 +-
>>   xen/arch/arm/traps.c                         |   72 +-
>>   xen/arch/x86/Kconfig                         |    1 +
>>   xen/arch/x86/hvm/dm.c                        |  107 +-
>>   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                     | 1375 ++-----------------------
>>   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.c                        |   17 +-
>>   xen/arch/x86/mm/shadow/common.c              |    2 +-
>>   xen/common/Kconfig                           |    3 +
>>   xen/common/Makefile                          |    1 +
>>   xen/common/ioreq.c                           | 1426 ++++++++++++++++++++++++++
>>   xen/common/memory.c                          |   72 +-
>>   xen/include/asm-arm/domain.h                 |    3 +
>>   xen/include/asm-arm/hvm/ioreq.h              |   72 ++
>>   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                  |   25 +
>>   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              |   39 +-
>>   xen/include/asm-x86/hvm/vcpu.h               |   18 -
>>   xen/include/asm-x86/mm.h                     |    4 -
>>   xen/include/asm-x86/p2m.h                    |   27 +-
>>   xen/include/public/arch-arm.h                |    5 +
>>   xen/include/public/hvm/dm_op.h               |   16 +
>>   xen/include/xen/dm.h                         |   39 +
>>   xen/include/xen/ioreq.h                      |  140 +++
>>   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 +-
>>   65 files changed, 3073 insertions(+), 1809 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/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
>>
>> --
>> 2.7.4
>>
-- 
Regards,

Oleksandr Tyshchenko