Re: [Xen-devel] [PATCH qemu-xen-traditional 1/2] xen_platform: unplug also SCSI disks [and 1 more messages]

[George Dunlap <dunlapg@xxxxxxxxx>]

On Mon, Jan 9, 2017 at 4:39 PM, Olaf Hering <olaf@xxxxxxxxx> wrote:
> On Mon, Jan 09, Ian Jackson wrote:
>
>> Olaf Hering writes ("[PATCH qemu-xen-traditional 2/2] xen_platform: SUSE 
>> xenlinux unplug for emulated PCI"):
>> > From: Olaf Hering <ohering@xxxxxxx>
>> >
>> > Implement SUSE specific unplug protocol for emulated PCI devices
>> > in PVonHVM guests. Its a simple 'outl(1, (ioaddr + 4));'.
>> > This protocol was implemented and used since Xen 3.0.4.
>> > It is used in all SUSE/SLES/openSUSE releases up to SLES11SP3 and
>> > openSUSE 12.3.
>> > In addition old (pre-2011) VMDP versions are handled as well.
>>
>> On the other hand, I am very reluctant to apply this.
>>
>> I don't see a good reason for SUSE to have a custom unplug protocol.
>> Why can't your guests use the standard one ?  Why haven't they been
>> updated to use the standard one some time in the last ?5-10 years ?
>
> The protocol was introduced before upstream had one, xen-3.0 vs.
> xen-3.x. I have not digged into 10 year old emails why it was done that
> way, if it was ever proposed for upstream inclusion. Meanwhile the
> upstream unplug is used since a two years. This patch would allow to run
> old SUSE domUs on new non-SUSE dom0s with qemu-trad.

We make efforts to allow guest OSes that use Hyper-V and VMWare
interfaces run properly, this seems small in comparison.

Given that SuSE kernels are now using the new unplug protocol, I think
there's no longer any reason to stand on principle.  We take a
practical approach for emulating other hypervisor interfaces (Hyper-V
and VMWare); making accomodation for "one of our own" seems pretty
reasonable.  (I haven't reviewed the patch itself.)

 -George

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel