Re: Possible LMB hot unplug bug in 4.13+ kernels

Nathan Fontenot [off-list ref] writes:

On 10/04/2017 03:21 PM, Daniel Henrique Barboza wrote:

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quoted

It appears that the hot unplug is failing because lmb_is_removable(lmb) is returning
false inside dlpar_remove_lmb, triggering the hotplug of the LMBs again:

...

quoted

I am not aware of anything that I can do from QEMU side to fix this. Can anyone take a look or provide
guidance? Am I missing something in my tests?

I don't think you are missing anything in your tests and am not sure that this is a bug.
DLPAR memory remove operations are not guaranteed, memory remove requests fail quite often
because the LMBs we are trying to remove are not removable.

From the added printks you put in this appears to be what is happening. When trying to
remove the range of LMBs, one of the memory sections in one of the LMBs is not removbable,
this is seen when lmb_is_removable() returns false.

Yeah I agree.

Unless you (Daniel) think there's some reason lmb_is_removable() is
incorrectly returning false. But most likely it's correct and there's
just an unmovable allocation in that range.

cheers