[Xen-devel] xl.cfg, memory options clarification

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

Hi there,

There is an issue with the usage of "maxmem" options with qemu-upstream 
and it's probably do to my understanding of the options "memory", 
"videoram" and "maxmem" from a xl config file.
I though "memory" is the amount of RAM that a guest will have. So qemu 
upstream will have this value as an amount of RAM and when qemu ask for 
the videoram, ...
But if we begin to play with the "maxmem" option, then the guest become 
unusable, depending of the value of maxmem, we can have eithier a "MMIO 
emulation failed" or the bios does not see any disk.
I also try something else with the default qemu, having memory=128 and 
maxmem=1024. The guest boot, but after using it a bit Xen print:
(XEN) p2m_pod_demand_populate: Out of populate-on-demand memory! 
tot_pages 31733 pod_entries 231424
(XEN) domain_crash called from p2m-pod.c:1076
[...]
(XEN) Panic on CPU 0:
(XEN) Assertion 'lock->recurse_cnt < 0xfu' failed at spinlock.c:251

and reboot.

Is maxmem not suppose to be used with a guest ? Or is just broken.

From all of that, I think I'll just make a change to the 
build_dm_args_new and give "-m $((maxmem - videoram))" instead of targetmem.
Regards,

--
Anthony PERARD

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