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Re: [PATCH v2 00/27] Enable PV backends with Xen/KVM emulation
- To: David Woodhouse <dwmw2@xxxxxxxxxxxxx>, qemu-devel@xxxxxxxxxx
- From: Paul Durrant <xadimgnik@xxxxxxxxx>
- Date: Tue, 7 Mar 2023 17:57:29 +0000
- Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>, Joao Martins <joao.m.martins@xxxxxxxxxx>, Ankur Arora <ankur.a.arora@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, vikram.garhwal@xxxxxxx, Anthony Perard <anthony.perard@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Juan Quintela <quintela@xxxxxxxxxx>, "Dr . David Alan Gilbert" <dgilbert@xxxxxxxxxx>, Peter Maydell <peter.maydell@xxxxxxxxxx>
- Delivery-date: Tue, 07 Mar 2023 17:57:36 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 07/03/2023 17:17, David Woodhouse wrote:
Following on from the basic platform support which has already been
merged, here's phase 2 which wires up the XenBus and PV back ends.
It starts with a basic single-tenant internal implementation of a
XenStore, with a copy-on-write tree, watches, transactions, quotas.
Then we introduce operations tables for the grant table, event channel,
foreignmen and xenstore operations so that in addition to using the Xen
libraries for those, QEMU can use its internal emulated versions.
A little bit of cleaning up of header files, and we can enable the build
of xen-bus in the CONFIG_XEN_EMU build, and run a Xen guest with an
actual PV disk...
qemu-system-x86_64 -serial mon:stdio -M q35 -display none -m 1G -smp 2 \
-accel kvm,xen-version=0x4000e,kernel-irqchip=split \
-kernel bzImage -append "console=ttyS0 root=/dev/xvda1 selinux=0" \
-drive file=/var/lib/libvirt/images/fedora28.qcow2,if=none,id=disk \
-device xen-disk,drive=disk,vdev=xvda
The main thing that isn't working here is migration. I've implemented it
for the internal xenstore and the unit tests exercise it, but the
existing PV back ends don't support it, perhaps partly because support
for guest transparent live migration support isn't upstream in Xen yet.
So the disk doesn't come back correctly after migration. I'm content
with that for 8.0 though, and we just mark the emulated XenStore device
as unmigratable to prevent users from trying.
The other pre-existing constraint is that only the block back end has
yet been ported to the "new" XenBus infrastructure, and is actually
capable of creating its own backend nodes. Again, I can live with
that for 8.0. Maybe this will motivate us to finally get round to
converting the rest off XenLegacyBackend and killing it.
We also don't have a simple way to perform grant mapping of multiple
guest pages to contiguous addresses, as we can under real Xen. So we
don't advertise max-ring-page-order for xen-disk in the emulated mode.
Fixing that — if we actually want to — would probably require mapping
RAM from an actual backing store object, so that it can be mapped again
at a different location for the PV back end to see.
v2: https://git.infradead.org/users/dwmw2/qemu.git/shortlog/refs/heads/xenfv-2
• Full set of reviewed-by tags from Paul (and associated minor fixes).
• Disable migration for emulated XenStore device.
• Update docs and add MAINTAINERS entry.
v1:
https://lore.kernel.org/qemu-devel/20230302153435.1170111-1-dwmw2@xxxxxxxxxxxxx/
https://git.infradead.org/users/dwmw2/qemu.git/shortlog/refs/heads/xenfv-1
David Woodhouse (23):
hw/xen: Add xenstore wire implementation and implementation stubs
hw/xen: Add basic XenStore tree walk and write/read/directory support
hw/xen: Implement XenStore watches
hw/xen: Implement XenStore transactions
hw/xen: Watches on XenStore transactions
hw/xen: Implement core serialize/deserialize methods for xenstore_impl
hw/xen: Add evtchn operations to allow redirection to internal emulation
hw/xen: Add gnttab operations to allow redirection to internal emulation
hw/xen: Pass grant ref to gnttab unmap operation
hw/xen: Add foreignmem operations to allow redirection to internal
emulation
hw/xen: Move xenstore_store_pv_console_info to xen_console.c
hw/xen: Use XEN_PAGE_SIZE in PV backend drivers
hw/xen: Rename xen_common.h to xen_native.h
hw/xen: Build PV backend drivers for CONFIG_XEN_BUS
hw/xen: Only advertise ring-page-order for xen-block if gnttab supports
it
hw/xen: Hook up emulated implementation for event channel operations
hw/xen: Add emulated implementation of grant table operations
hw/xen: Add emulated implementation of XenStore operations
hw/xen: Map guest XENSTORE_PFN grant in emulated Xenstore
hw/xen: Implement soft reset for emulated gnttab
i386/xen: Initialize Xen backends from pc_basic_device_init() for
emulation
MAINTAINERS: Add entry for Xen on KVM emulation
docs: Update Xen-on-KVM documentation for PV disk support
Paul Durrant (4):
hw/xen: Implement XenStore permissions
hw/xen: Create initial XenStore nodes
hw/xen: Add xenstore operations to allow redirection to internal
emulation
hw/xen: Avoid crash when backend watch fires too early
MAINTAINERS | 9 +
accel/xen/xen-all.c | 69 +-
docs/system/i386/xen.rst | 30 +-
hw/9pfs/meson.build | 2 +-
hw/9pfs/xen-9p-backend.c | 32 +-
hw/block/dataplane/meson.build | 2 +-
hw/block/dataplane/xen-block.c | 12 +-
hw/block/meson.build | 2 +-
hw/block/xen-block.c | 12 +-
hw/char/meson.build | 2 +-
hw/char/xen_console.c | 57 +-
hw/display/meson.build | 2 +-
hw/display/xenfb.c | 32 +-
hw/i386/kvm/meson.build | 1 +
hw/i386/kvm/trace-events | 15 +
hw/i386/kvm/xen_evtchn.c | 15 +
hw/i386/kvm/xen_gnttab.c | 325 ++++-
hw/i386/kvm/xen_gnttab.h | 1 +
hw/i386/kvm/xen_xenstore.c | 1251 +++++++++++++++-
hw/i386/kvm/xenstore_impl.c | 1927 +++++++++++++++++++++++++
hw/i386/kvm/xenstore_impl.h | 63 +
hw/i386/pc.c | 7 +
hw/i386/pc_piix.c | 4 +-
hw/i386/xen/xen-hvm.c | 38 +-
hw/i386/xen/xen-mapcache.c | 2 +-
hw/i386/xen/xen_platform.c | 7 +-
hw/net/xen_nic.c | 25 +-
hw/usb/meson.build | 2 +-
hw/usb/xen-usb.c | 29 +-
hw/xen/meson.build | 6 +-
hw/xen/trace-events | 2 +-
hw/xen/xen-bus-helper.c | 62 +-
hw/xen/xen-bus.c | 411 +-----
hw/xen/xen-legacy-backend.c | 254 +---
hw/xen/xen-operations.c | 478 ++++++
hw/xen/xen_devconfig.c | 4 +-
hw/xen/xen_pt.c | 2 +-
hw/xen/xen_pt.h | 2 +-
hw/xen/xen_pt_config_init.c | 2 +-
hw/xen/xen_pt_graphics.c | 1 -
hw/xen/xen_pt_msi.c | 4 +-
hw/xen/xen_pvdev.c | 63 +-
include/hw/xen/xen-bus-helper.h | 26 +-
include/hw/xen/xen-bus.h | 21 +-
include/hw/xen/xen-legacy-backend.h | 24 +-
include/hw/xen/xen.h | 24 +-
include/hw/xen/xen_backend_ops.h | 408 ++++++
include/hw/xen/{xen_common.h => xen_native.h} | 75 +-
include/hw/xen/xen_pvdev.h | 6 +-
softmmu/globals.c | 4 +
target/i386/kvm/xen-emu.c | 5 +
tests/unit/meson.build | 1 +
tests/unit/test-xs-node.c | 871 +++++++++++
53 files changed, 5804 insertions(+), 927 deletions(-)
I think the series is good to go now so time to send a PR.
Cheers,
Paul
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