Failure to allocate HTAB for guest - CMA allocation failures?

Balbir Singh bsingharora at
Mon May 21 16:53:32 AEST 2018

On Fri, 18 May 2018 01:13:31 +1000
Daniel Axtens <dja at> wrote:

> I noticed from [1] that there is a patch from Balbir that apparently
> helps when VFIO is used - 2e5bbb5461f1 ("KVM: PPC: Book3S HV: Migrate
> pinned pages out of CMA"). The user is running a 4.4 kernel with this
> backported.

Hmm.. there are two possible scenarios

1. We got movable allocations in the CMA region, these should be migrated 
out on their own
2. We've got pinned allocations in the CMA region and hence movable won't
work with them. We do have trace events for cma_alloc/cma_release if you
want to look them.

Your right in that we'll try to allocate 128 MB from
the CMA region (based on the 1/128th calculation that I remember). If we
can figure out what's allocated memory in the CMA region we can debug
this further. Do the sum of HPT allocations add up to the used CMA memory?

Balbir Singh.

More information about the Linuxppc-dev mailing list