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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [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
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