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Re: [PATCH 4/4] vl: Prioritize realizations of devices
From: |
Peter Xu |
Subject: |
Re: [PATCH 4/4] vl: Prioritize realizations of devices |
Date: |
Tue, 24 Aug 2021 15:52:41 -0400 |
On Tue, Aug 24, 2021 at 06:24:27PM +0200, David Hildenbrand wrote:
> > > Not so much; here's the list of priorities and the devices using it:
> > >
> > > |--------------------+---------|
> > > | priority | devices |
> > > |--------------------+---------|
> > > | MIG_PRI_IOMMU | 3 |
> > > | MIG_PRI_PCI_BUS | 7 |
> > > | MIG_PRI_VIRTIO_MEM | 1 |
> > > | MIG_PRI_GICV3_ITS | 1 |
> > > | MIG_PRI_GICV3 | 1 |
> > > |--------------------+---------|
> >
> > iommu is probably ok. I think virtio mem is ok too,
> > in that it is normally created by virtio-mem-pci ...
>
> IIRC:
>
> intel-iommu has to be created on the QEMU cmdline before creating
> virtio-mem-pci.
>
> -device intel-iommu,caching-mode=on,intremap=on,device-iotlb=on \
> ...
> -device
> virtio-mem-pci,disable-legacy=on,disable-modern=off,iommu_platform=on,ats=on,id=vm0,...
>
> Creating virtio-mem-pci will implicitly create virtio-mem. virtio-mem device
> state has to be migrated before migrating intel-iommu state.
Since we're at it.. frankly I didn't fully digest why virtio-mem needs to be
migrated before when reading commit 0fd7616e0f1171b. It gives me the feeling
more like that virtio-mem has a ordering dependency with vfio-pci not
virtio-mem, but I could be wrong.
E.g., the IOMMU unit shouldn't be walking page table if without a device using
it, then it won't fail until the device walks it in region_add() hooks when
memory replay happens.
>
> I do wonder if migration priorities are really what we want to reuse here. I
> guess it works right, but just by pure luck (because we ignore the implicit
> dependency regarding priorities)
Yep, that's probably not what we want. I'll make it a new list of priorities
as I've stated in the other thread.
Thanks,
--
Peter Xu
- Re: [PATCH 4/4] vl: Prioritize realizations of devices, (continued)
- Re: [PATCH 4/4] vl: Prioritize realizations of devices, Eduardo Habkost, 2021/08/23
- Re: [PATCH 4/4] vl: Prioritize realizations of devices, Peter Xu, 2021/08/23
- Re: [PATCH 4/4] vl: Prioritize realizations of devices, Michael S. Tsirkin, 2021/08/23
- Re: [PATCH 4/4] vl: Prioritize realizations of devices, Peter Xu, 2021/08/23
- Re: [PATCH 4/4] vl: Prioritize realizations of devices, Jason Wang, 2021/08/23
- Re: [PATCH 4/4] vl: Prioritize realizations of devices, Peter Xu, 2021/08/24
- Re: [PATCH 4/4] vl: Prioritize realizations of devices, Jason Wang, 2021/08/25
- Re: [PATCH 4/4] vl: Prioritize realizations of devices, David Hildenbrand, 2021/08/24
- Re: [PATCH 4/4] vl: Prioritize realizations of devices,
Peter Xu <=
- Re: [PATCH 4/4] vl: Prioritize realizations of devices, David Hildenbrand, 2021/08/25
- Re: [PATCH 4/4] vl: Prioritize realizations of devices, Jason Wang, 2021/08/23