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Re: [Xen-devel] [PATCH v2] libxl: change default QEMU machine to pc-i440fx-1.6




On 07/11/14 11:08, Ian Campbell wrote:
On Fri, 2014-07-11 at 15:54 +0100, Stefano Stabellini wrote:
On Fri, 11 Jul 2014, Ian Campbell wrote:
On Fri, 2014-07-11 at 12:14 +0100, Stefano Stabellini wrote:
On Thu, 10 Jul 2014, Ian Jackson wrote:
Stefano Stabellini writes ("Re: [PATCH v2] libxl: change default QEMU machine to 
pc-i440fx-1.6"):

If we use -M pc or -M pc-i440fx-1.6, the xen-platform-pci device is
created slightly later in the QEMU boot sequence. The Intel HDA device
is able to "steal" its slot on the PCI bus.

On the other hand it is worth pointing out that currently libxl switches
from -M xenfv to -M pc silently depending on whether the
xen_platform_pci option is enabled or disabled. If it is disabled we get
pc, that is a moving target and not guaranteed to be compatible with
anything.
Changing that option is a guest reboot scenario, which is completely
different to a migration. I think it is (just about) OK for the PCI id
to change on a reboot, but it certainly isn't OK on migrate.

If you can't get the platform device created earlier then perhaps you
can find a way to influence the slot used by the hda device?

Ian.

I see 2 options:

1) change only the -M pc to -M pc-i440fx-1.6 (I.E. continue to use xenfv)

2) Add ",addr=0x1.0x0" to the xen platform device.  (Which will cause
    QEMU to abort in this case.)  Also fix soundhw handling to stop using
    "-soundhw", and switch to "--device intel-hda,addr=0x12.0x0 -device
    hda-duplex" etc.


As a side note on #1, I do have a hack to allow adjusting the placement
of the xen platform device (adding a new xl.cfg option for it), but is not
ready to be a patch.  It would allow still using "-soundhw" "hda" but would
require a config change.

   -Don Slutz



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