Re: [PATCH v4 00/21] virtio-mem: Paravirtualized memory hot(un)plug

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jun 10, 2020 at 01:53:58PM +0200, David Hildenbrand wrote:
> This is the very basic, initial version of virtio-mem. More info on
> virtio-mem in general can be found in the Linux kernel driver v2 posting
> [1] and in patch #10. The Linux driver is currently on its way upstream.
> 
> This series is based on [3]:
>     "[PATCH v1] pc: Support coldplugging of virtio-pmem-pci devices on all
>      buses"
> And [4]:
>     "[PATCH v2] hmp: Make json format optional for qom-set"
> 
> The patches can be found at:
>     https://github.com/davidhildenbrand/qemu.git virtio-mem-v4


OK so looks sane to me.
IIUC there are a couple of minor tweaks still so I'm expecting v5
of this.
You want me to merge this, right?


> "The basic idea of virtio-mem is to provide a flexible,
> cross-architecture memory hot(un)plug solution that avoids many limitations
> imposed by existing technologies, architectures, and interfaces."
> 
> There are a lot of addons in the works (esp. protection of unplugged
> memory, better hugepage support (esp. when reading unplugged memory),
> resizeable memory backends, support for more architectures, ...), this is
> the very basic version to get the ball rolling.
> 
> The first 8 patches make sure we don't have any sudden surprises e.g., if
> somebody tries to pin all memory in RAM blocks, resulting in a higher
> memory consumption than desired. The remaining patches add basic virtio-mem
> along with support for x86-64. The last patch indicates to the guest OS
> the maximum possible PFN using ACPI SRAT, such that Linux can properly
> enable the swiotlb when booting only with DMA memory.
> 
> [1] https://lkml.kernel.org/r/20200311171422.10484-1-david@redhat.com
> [2] https://lkml.kernel.org/r/20200507140139.17083-1-david@redhat.com
> [3] https://lkml.kernel.org/r/20200525084511.51379-1-david@redhat.com
> [3] https://lkml.kernel.org/r/20200610075153.33892-1-david@redhat.com
> 
> Based-on: <20200525084511.51379-1-david@redhat.com>
> Based-on: <20200610075153.33892-1-david@redhat.com>
> Cc: teawater <teawaterz@linux.alibaba.com>
> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> 
> v3 -> v4
> - Adapt to virtio-mem config layout change (block size now is 64bit)
> - Added "numa: Auto-enable NUMA when any memory devices are possible"
> 
> v2 -> v3:
> - Rebased on upstream/[3]
> - "virtio-mem: Exclude unplugged memory during migration"
> -- Added
> - "virtio-mem: Paravirtualized memory hot(un)plug"
> -- Simplify bitmap operations, find consecutive areas
> -- Tweak error messages
> -- Reshuffle some checks
> -- Minor cleanups
> - "accel/kvm: Convert to ram_block_discard_disable()"
> - "target/i386: sev: Use ram_block_discard_disable()"
> -- Keep asserts clean of functional things
> 
> v1 -> v2:
> - Rebased to object_property_*() changes
> - "exec: Introduce ram_block_discard_(disable|require)()"
> -- Change the function names and rephrase/add comments
> - "virtio-balloon: Rip out qemu_balloon_inhibit()"
> -- Add and use "migration_in_incoming_postcopy()"
> - "migration/rdma: Use ram_block_discard_disable()"
> -- Add a comment regarding pin_all vs. !pin_all
> - "virtio-mem: Paravirtualized memory hot(un)plug"
> -- Replace virtio_mem_discard_inhibited() by
>    migration_in_incoming_postcopy()
> -- Drop some asserts
> -- Drop virtio_mem_bad_request(), use virtio_error() directly, printing
>    more information
> -- Replace "Note: Discarding should never fail ..." comments by
>    error_report()
> -- Replace virtio_stw_p() by cpu_to_le16()
> -- Drop migration_addr and migration_block_size
> -- Minor cleanups
> - "linux-headers: update to contain virtio-mem"
> -- Updated to latest v4 in Linux
> - General changes
> -- Fixup the users of the renamed ram_block_discard_(disable|require)
> -- Use "X: cannot disable RAM discard"-styled error messages
> - Added
> -- "virtio-mem: Migration sanity checks"
> -- "virtio-mem: Add trace events"
> 
> David Hildenbrand (21):
>   exec: Introduce ram_block_discard_(disable|require)()
>   vfio: Convert to ram_block_discard_disable()
>   accel/kvm: Convert to ram_block_discard_disable()
>   s390x/pv: Convert to ram_block_discard_disable()
>   virtio-balloon: Rip out qemu_balloon_inhibit()
>   target/i386: sev: Use ram_block_discard_disable()
>   migration/rdma: Use ram_block_discard_disable()
>   migration/colo: Use ram_block_discard_disable()
>   linux-headers: update to contain virtio-mem
>   virtio-mem: Paravirtualized memory hot(un)plug
>   virtio-pci: Proxy for virtio-mem
>   MAINTAINERS: Add myself as virtio-mem maintainer
>   hmp: Handle virtio-mem when printing memory device info
>   numa: Handle virtio-mem in NUMA stats
>   pc: Support for virtio-mem-pci
>   virtio-mem: Allow notifiers for size changes
>   virtio-pci: Send qapi events when the virtio-mem size changes
>   virtio-mem: Migration sanity checks
>   virtio-mem: Add trace events
>   virtio-mem: Exclude unplugged memory during migration
>   numa: Auto-enable NUMA when any memory devices are possible
> 
>  MAINTAINERS                                 |   8 +
>  accel/kvm/kvm-all.c                         |   4 +-
>  balloon.c                                   |  17 -
>  exec.c                                      |  52 ++
>  hw/arm/virt.c                               |   2 +
>  hw/core/numa.c                              |  17 +-
>  hw/i386/Kconfig                             |   1 +
>  hw/i386/microvm.c                           |   1 +
>  hw/i386/pc.c                                |  50 +-
>  hw/i386/pc_piix.c                           |   1 +
>  hw/i386/pc_q35.c                            |   1 +
>  hw/s390x/s390-virtio-ccw.c                  |  22 +-
>  hw/vfio/ap.c                                |  10 +-
>  hw/vfio/ccw.c                               |  11 +-
>  hw/vfio/common.c                            |  53 +-
>  hw/vfio/pci.c                               |   6 +-
>  hw/virtio/Kconfig                           |  11 +
>  hw/virtio/Makefile.objs                     |   2 +
>  hw/virtio/trace-events                      |  10 +
>  hw/virtio/virtio-balloon.c                  |   8 +-
>  hw/virtio/virtio-mem-pci.c                  | 157 ++++
>  hw/virtio/virtio-mem-pci.h                  |  34 +
>  hw/virtio/virtio-mem.c                      | 872 ++++++++++++++++++++
>  include/exec/memory.h                       |  41 +
>  include/hw/boards.h                         |   1 +
>  include/hw/pci/pci.h                        |   1 +
>  include/hw/vfio/vfio-common.h               |   4 +-
>  include/hw/virtio/virtio-mem.h              |  86 ++
>  include/migration/colo.h                    |   2 +-
>  include/migration/misc.h                    |   2 +
>  include/standard-headers/linux/virtio_ids.h |   1 +
>  include/standard-headers/linux/virtio_mem.h | 211 +++++
>  include/sysemu/balloon.h                    |   2 -
>  migration/migration.c                       |  15 +-
>  migration/postcopy-ram.c                    |  23 -
>  migration/rdma.c                            |  18 +-
>  migration/savevm.c                          |  11 +-
>  monitor/hmp-cmds.c                          |  16 +
>  monitor/monitor.c                           |   1 +
>  qapi/misc.json                              |  64 +-
>  target/i386/sev.c                           |   7 +
>  41 files changed, 1730 insertions(+), 126 deletions(-)
>  create mode 100644 hw/virtio/virtio-mem-pci.c
>  create mode 100644 hw/virtio/virtio-mem-pci.h
>  create mode 100644 hw/virtio/virtio-mem.c
>  create mode 100644 include/hw/virtio/virtio-mem.h
>  create mode 100644 include/standard-headers/linux/virtio_mem.h
> 
> -- 
> 2.26.2