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Re: [Qemu-devel] [RFC PATCH V2 00/10] Qemu: Add live migration support f
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [RFC PATCH V2 00/10] Qemu: Add live migration support for SRIOV NIC |
Date: |
Mon, 30 Nov 2015 10:01:18 +0200 |
On Tue, Nov 24, 2015 at 09:35:17PM +0800, Lan Tianyu wrote:
> This patchset is to propose a solution of adding live migration
> support for SRIOV NIC.
>
> During migration, Qemu needs to let VF driver in the VM to know
> migration start and end. Qemu adds faked PCI migration capability
> to help to sync status between two sides during migration.
>
> Qemu triggers VF's mailbox irq via sending MSIX msg when migration
> status is changed. VF driver tells Qemu its mailbox vector index
> via the new PCI capability. In some cases(NIC is suspended or closed),
> VF mailbox irq is freed and VF driver can disable irq injecting via
> new capability.
>
> VF driver will put down nic before migration and put up again on
> the target machine.
It is still not very clear what it is you are trying to achieve, and
whether your patchset achieves it. You merely say "adding live
migration" but it seems pretty clear this isn't about being able to
migrate a guest transparently, since you are adding a host/guest
handshake.
This isn't about functionality either: I think that on KVM, it isn't
hard to live migrate if you can do a host/guest handshake, even today,
with no kernel changes:
1. before migration, expose a pv nic to guest (can be done directly on
boot)
2. use e.g. a serial connection to move IP from an assigned device to pv nic
3. maybe move the mac as well
4. eject the assigned device
5. detect eject on host (QEMU generates a DEVICE_DELETED event when this
happens) and start migration
Is this patchset a performance optimization then?
If yes it needs to be accompanied with some performance numbers.
--
MST
- [Qemu-devel] [RFC PATCH V2 04/10] Qemu/VFIO: Add vfio_find_free_cfg_reg() to find free PCI config space regs, (continued)
- [Qemu-devel] [RFC PATCH V2 04/10] Qemu/VFIO: Add vfio_find_free_cfg_reg() to find free PCI config space regs, Lan Tianyu, 2015/11/24
- [Qemu-devel] [RFC PATCH V2 05/10] Qemu/VFIO: Expose PCI config space read/write and msix functions, Lan Tianyu, 2015/11/24
- [Qemu-devel] [RFC PATCH V2 07/10] Qemu: Add post_load_state() to run after restoring CPU state, Lan Tianyu, 2015/11/24
- [Qemu-devel] [RFC PATCH V2 06/10] Qemu/PCI: Add macros for faked PCI migration capability, Lan Tianyu, 2015/11/24
- [Qemu-devel] [RFC PATCH V2 08/10] Qemu: Add save_before_stop callback to run just before stopping VCPU during migration, Lan Tianyu, 2015/11/24
- [Qemu-devel] [RFC PATCH V2 09/10] Qemu/VFIO: Add SRIOV VF migration support, Lan Tianyu, 2015/11/24
- [Qemu-devel] [RFC PATCH V2 10/10] Qemu/VFIO: Misc change for enable migration with VFIO, Lan Tianyu, 2015/11/24
- Re: [Qemu-devel] [RFC PATCH V2 00/10] Qemu: Add live migration support for SRIOV NIC,
Michael S. Tsirkin <=