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

[Fabio Fantoni <fabio.fantoni@xxxxxxx>]

Il 26/05/2014 10:00, Fabio Fantoni ha scritto:
> Il 25/05/2014 16:14, Stefano Stabellini ha scritto:
> > On Fri, 23 May 2014, Fabio Fantoni wrote:
> > > Il 23/05/2014 18:07, Stefano Stabellini ha scritto:
> > > > Choose pc-i440fx-1.6 instead of pc for HVM guests, so that we know for
> > > > sure what is the machine that we are emulating.
> > > >
> > > > Use pc-i440fx-1.6 regardless of the xen_platform_pci option. Add the
> > > > xen-platform device if requested. Choose slot 2 for the xen-platform
> > > > device for compatibility with current installations. In case of Intel
> > > > graphic passthrough, slot 2 might be needed by the grafic card. 
> > > > However
> > > > now that we can specify the slot explicitly, it is easy to change the
> > > > position of the xen-platform device on the PCI bus if graphic
> > > > passthrough is enabled.
> > > >
> > > > Move the machine options earlier, before any other emulated devices
> > > > options. Otherwise the selected PCI slot for the xen-platform 
> > > > device is
> > > > not available in QEMU.
> > > >
> > > > Specify PIIX4_PM.acpi-pci-hotplug-with-bridge-support=off, because
> > > > differently from xenfv, the other QEMU machines do not have that 
> > > > option
> > > > off by default.
> > > >
> > > > This patch does not change the emulated environment in the guest.
> > > >
> > > > Refer to this thread: 
> > > > http://marc.info/?l=xen-devel&m=140023775929625&w=2
> > > > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > > >
> > > > diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
> > > > index 8abed7b..fef684f 100644
> > > > --- a/tools/libxl/libxl_dm.c
> > > > +++ b/tools/libxl/libxl_dm.c
> > > > @@ -476,6 +476,29 @@ static char **
> > > > libxl__build_device_model_args_new(libxl__gc *gc,
> > > >            flexarray_vappend(dm_args, "-k", keymap, NULL);
> > > >        }
> > > >    +    flexarray_append(dm_args, "-machine");
> > > > +    switch (b_info->type) {
> > > > +    case LIBXL_DOMAIN_TYPE_PV:
> > > > +        flexarray_append(dm_args, "xenpv");
> > > > +        for (i = 0; b_info->extra_pv && b_info->extra_pv[i] != 
> > > > NULL; i++)
> > > > +            flexarray_append(dm_args, b_info->extra_pv[i]);
> > > > +        break;
> > > > +    case LIBXL_DOMAIN_TYPE_HVM:
> > > > +        flexarray_append(dm_args, "pc-i440fx-1.6,accel=xen");
> I think that a note in README should be added: qemu >=1.6.1 is 
> required for hvm domUs.
> About the other xl parameter to be added I think that should be:
> qemu_machine_type="i440fx"|"q35" (when also q35 will be supported on xen)
> qemu_machine_version="x.y" to specify the machine version, useful for 
> debug/testing and other some cases.
> > > > +        flexarray_append(dm_args, "-global");
> > > > +        flexarray_append(dm_args,
> > > > "PIIX4_PM.acpi-pci-hotplug-with-bridge-support=off");
> > > I think is good add a comment for remember to remove this workaround 
> > > when pc
> > > > =2.1 will be the default since qemu 2.1 will fix it.
> > > https://lists.gnu.org/archive/html/qemu-devel/2014-05/msg04789.html
> > The workaround is not actually harmful, it doesn't need to be removed
> > when pc >= 2.1 in QEMU.
> >
> >
> > > > +        if (libxl_defbool_val(b_info->u.hvm.xen_platform_pci)) {
> > > > +            flexarray_append(dm_args, "-device");
> > > > +            flexarray_append(dm_args, "xen-platform,addr=0x2");
> > > The fixed pci address to 0x2 probably is a problem with intel gpu 
> > > passthrough:
> > > http://lists.gnu.org/archive/html/qemu-devel/2014-05/msg03726.html
> > Right, however we cannot really change the default position of the
> > xen-platform device on the PCI bus, otherwise we'll end up changing the
> > emulated environment for all the VMs out there.
> >
> > I'll leave it to Tiejun to move xen-platform to another slot when
> > graphic passthrough is enabled.
I found another case of problem with xen-platform's fixed pci slot.
I tested this patch and I saw that qemu not start also in other cases, 
for example the domU of my test:
> qemu-system-i386: -device xen-platform,addr=0x2: PCI: slot 2 function 
> 0 not available for xen-platform, in use by intel-hda
> qemu-system-i386: -device xen-platform,addr=0x2: Device initialization 
> failed.
> qemu-system-i386: -device xen-platform,addr=0x2: Device 'xen-platform' 
> could not be initialized
The domU's xl cfg:
> name='W7'
> builder="hvm"
> #device_model_override="/usr/lib/xen/bin/qemu-gdb"
> #device_model_override="/usr/bin/qemu-system-x86_64"
> #bios="ovmf"
> memory=2048
> vcpus=2
> #nestedhvm=1
> #vif=['model=e1000,bridge=xenbr0']
> vif=['bridge=xenbr0,mac=00:16:3e:42:ae:8f']
> disk=['/mnt/vm/disks/W7.disk1.xm,raw,hda,rw',',raw,hdb,ro,cdrom']
> boot='dc'
> device_model_version="qemu-xen"
> viridian=1
> vnc=0
> keymap="it"
> on_crash="destroy"
> vga="qxl"
> #videoram=64
> spice=1
> spicehost='0.0.0.0'
> spiceport=6002
> spicedisable_ticketing=1
> spicevdagent=1
> spice_clipboard_sharing=0
> spice_image_compression="off"
> spice_streaming_video="filter"
> spiceusbredirection=4
> soundhw="hda"
> localtime=1
> usbversion=2
Probably there are also other cases that can create a problem with 
xen-platform fixed address, FWIK now new usb controller (with 
usbversion) is the only other with fixed pci address in libxl, all other 
emulated qemu components not.
And call it before in qemu binary starts notaffect the pci slot order 
because the xen-platform is already before audio.
Thanks for any reply and sorry for my bad english.


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