At Wed, 14 Apr 2021 19:53:47 +0200, Jaromír Doleček <jaromir.dolecek%gmail.com@localhost> wrote: Subject: Re: one remaining mystery about the FreeBSD domU failure on NetBSD XEN3_DOM0 > > You can test if this is the problem by disabling the feature in > negotiation in NetBSD xbdback.c - comment out the code which sets > feature-max-indirect-segments in xbdback_backend_changed(). With the > feature disabled, FreeBSD DomU should not use indirect segments. Ah, yes, thanks! I should have thought of that. That's especially useful since on the client side it's a read-only flag: # sysctl -w hw.xbd.xbd_enable_indirect=0 sysctl: oid 'hw.xbd.xbd_enable_indirect' is a read only tunable sysctl: Tunable values are set in /boot/loader.conf Apparently in the Linux implementation the number of indirect segments used by a domU can be tuned at boot time, and that appears to be done by setting a driver option on the guest kernel command line. When I first read that it didn't make so much sense to me to be giving this kind of control to the domU. Perhaps it would be better to make this a tuneable in xl.cfg(5) such that it can be tuned on a per-guest basis. Then setting it to zero for a given guest would not advertise the feature at all. I've some other things to do before I can reboot -- I'll report as soon as that's done.... -- Greg A. Woods <gwoods%acm.org@localhost> Kelowna, BC +1 250 762-7675 RoboHack <woods%robohack.ca@localhost> Planix, Inc. <woods%planix.com@localhost> Avoncote Farms <woods%avoncote.ca@localhost>
Attachment:
pgp3izTFMiKab.pgp
Description: OpenPGP Digital Signature