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Re: [Qemu-ppc] [PATCH v3] virtio-pci: fix migration for pci bus master

From: Alexander Graf
Subject: Re: [Qemu-ppc] [PATCH v3] virtio-pci: fix migration for pci bus master
Date: Mon, 20 Oct 2014 18:08:56 +0200
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:31.0) Gecko/20100101 Thunderbird/31.1.2

On 20.10.14 08:58, Michael S. Tsirkin wrote:
> Current support for bus master (clearing OK bit) together with the need to
> support guests which do not enable PCI bus mastering, leads to extra state in
> VIRTIO_PCI_FLAG_BUS_MASTER_BUG bit, which isn't robust in case of 
> cross-version
> migration for the case when guests use the device before setting DRIVER_OK.
> Rip out this code, and replace it:
> -   Modern QEMU doesn't need VIRTIO_PCI_FLAG_BUS_MASTER_BUG
>     so just drop it for latest machine type.
> -   For compat machine types, set PCI_COMMAND if DRIVER_OK
>     is set.
> As this is needed for 2.1 for both pc and ppc, move PC_COMPAT macros from pc.h
> to a new common header.
> Reviewed-by: Greg Kurz <address@hidden>
> Tested-by: Greg Kurz <address@hidden>
> Signed-off-by: Michael S. Tsirkin <address@hidden>
> ---
> Alexander, could you pls ack me merging this?
> Thanks!

Have you tried whether this works with old kernel versions? We
introduced the broken flag for very specific old kernel versions that
got their flags wrong IIRC.


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