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Re: [Qemu-devel] [PATCH 10/12] spapr_pci: (Mostly) remove spapr-pci-vfio
From: |
David Gibson |
Subject: |
Re: [Qemu-devel] [PATCH 10/12] spapr_pci: (Mostly) remove spapr-pci-vfio-host-bridge |
Date: |
Mon, 29 Feb 2016 14:06:44 +1100 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
On Mon, Feb 29, 2016 at 12:42:28PM +1100, Alexey Kardashevskiy wrote:
> On 02/26/2016 10:32 PM, David Gibson wrote:
> >Now that the regular spapr-pci-host-bridge can handle EEH, there are only
> >two things that spapr-pci-vfio-host-bridge does differently:
> > 1. automatically sizes its DMA window to match the host IOMMU
> > 2. checks if the attached VFIO container is backed by the
> > VFIO_SPAPR_TCE_IOMMU type on the host
> >
> >(1) is not particularly useful, since the default window used by the
> >regular host bridge will work with the host IOMMU configuration on all
> >current systems anyway.
> >
> >Plus, automatically changing guest visible configuration (such as the DMA
> >window) based on host settings is generally a bad idea.
>
> btw why exactly is it a bad idea?
So, as noted, in this case it's probably ok. But in general changing
configuration based on host state will break migration, because the
source and destination VMs, with apparently identical setup won't
actually be the same.
It also makes it more difficult for management layers to know exactly
what they're constructing, which is potentially an issue even for this
non-migratable device.
>
>
> Anyway,
> Reviewed-by: Alexey Kardashevskiy <address@hidden>
>
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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- [Qemu-devel] [PATCH 02/12] spapr_pci: Switch to vfio_eeh_as_op() interface, (continued)
- [Qemu-devel] [PATCH 02/12] spapr_pci: Switch to vfio_eeh_as_op() interface, David Gibson, 2016/02/26
- [Qemu-devel] [PATCH 11/12] spapr_pci: Remove finish_realize hook, David Gibson, 2016/02/26
- [Qemu-devel] [PATCH 03/12] spapr_pci: Eliminate class callbacks, David Gibson, 2016/02/26
- [Qemu-devel] [PATCH 10/12] spapr_pci: (Mostly) remove spapr-pci-vfio-host-bridge, David Gibson, 2016/02/26
- [Qemu-devel] [PATCH 06/12] spapr_pci: Fold spapr_phb_vfio_eeh_get_state() into spapr_pci code, David Gibson, 2016/02/26
- [Qemu-devel] [PATCH 04/12] spapr_pci: Fold spapr_phb_vfio_eeh_configure() into spapr_pci code, David Gibson, 2016/02/26
Re: [Qemu-devel] [PATCH 00/12] Allow EEH on spapr-pci-host-bridge devices, David Gibson, 2016/02/26