Re: [PATCH v2 0/4] hw/arm/virt: Support dirty ring

[Gavin Shan <gshan@redhat.com>]

On 2/27/23 12:26 PM, Gavin Shan wrote:
> This series intends to support dirty ring for live migration for arm64. The
> dirty ring use discrete buffer to track dirty pages. For arm64, the speciality
> is to use backup bitmap to track dirty pages when there is no-running-vcpu
> context. It's known that the backup bitmap needs to be synchronized when
> KVM device "kvm-arm-gicv3" or "arm-its-kvm" has been enabled. The backup
> bitmap is collected in the last stage of migration. The policy here is to
> always enable the backup bitmap extension. The overhead to synchronize the
> backup bitmap in the last stage of migration, when those two devices aren't
> used, is introduced. However, the overhead should be very small and acceptable.
> The benefit is to support future cases where those two devices are used without
> modifying the code.
> 
> PATCH[1] add migration last stage indicator
> PATCH[2] synchronize the backup bitmap in the last stage of migration
> PATCH[3] add helper kvm_dirty_ring_init() to enable dirty ring
> PATCH[4] enable dirty ring for arm64
> 
>     v1: https://lists.nongnu.org/archive/html/qemu-arm/2023-02/msg00434.html
> RFCv1: https://lists.nongnu.org/archive/html/qemu-arm/2023-02/msg00171.html
> 
> Testing
> =======
> (1) kvm-unit-tests/its-pending-migration and kvm-unit-tests/its-migration with
>      dirty ring or normal dirty page tracking mechanism. All test cases passed.
> 
>      QEMU=./qemu.main/build/qemu-system-aarch64 ACCEL=kvm \
>      ./its-pending-migration
> 
>      QEMU=./qemu.main/build/qemu-system-aarch64 ACCEL=kvm \
>      ./its-migration
> 
>      QEMU=./qemu.main/build/qemu-system-aarch64 ACCEL=kvm,dirty-ring-size=65536 \
>      ./its-pending-migration
> 
>      QEMU=./qemu.main/build/qemu-system-aarch64 ACCEL=kvm,dirty-ring-size=65536 \
>      ./its-migration
> 
> (2) Combinations of migration, post-copy migration, e1000e and virtio-net
>      devices. All test cases passed.
> 
>      -netdev tap,id=net0,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown  \
>      -device e1000e,bus=pcie.5,netdev=net0,mac=52:54:00:f1:26:a0
> 
>      -netdev tap,id=vnet0,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown \
>      -device virtio-net-pci,bus=pcie.6,netdev=vnet0,mac=52:54:00:f1:26:b0
> 
> Changelog
> =========
> v2:
>    * Drop PATCH[v1 1/6] to synchronize linux-headers                            (Gavin)
>    * More restrictive comments about struct MemoryListener::log_sync_global     (PeterX)
>    * Always enable the backup bitmap extension                                  (PeterM)
> v1:
>    * Combine two patches into one PATCH[v1 2/6] for the last stage indicator    (PeterX)
>    * Drop the secondary bitmap and use the original one directly                (Juan)
>    * Avoid "goto out" in helper kvm_dirty_ring_init()                           (Juan)
> 

Ping, Paolo and Peter Maydell. Please take a look to see if it can be
merged, thanks!

> 
> Gavin Shan (4):
>    migration: Add last stage indicator to global dirty log
>      synchronization
>    kvm: Synchronize the backup bitmap in the last stage
>    kvm: Add helper kvm_dirty_ring_init()
>    kvm: Enable dirty ring for arm64
> 
>   accel/kvm/kvm-all.c      | 108 ++++++++++++++++++++++++++++-----------
>   include/exec/memory.h    |   7 ++-
>   include/sysemu/kvm_int.h |   1 +
>   migration/dirtyrate.c    |   4 +-
>   migration/ram.c          |  20 ++++----
>   softmmu/memory.c         |  10 ++--
>   6 files changed, 101 insertions(+), 49 deletions(-)
>