At Wed, 14 Apr 2021 19:53:47 +0200, Jaromír Doleček <jaromir.dole...@gmail.com> 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 <gwo...@acm.org>
Kelowna, BC +1 250 762-7675 RoboHack <wo...@robohack.ca>
Planix, Inc. <wo...@planix.com> Avoncote Farms <wo...@avoncote.ca>
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