From: David Hildenbrand on
gitlab.com
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1023#note_5523...
Sure, but keep in mind that it will be tech preview and is similarly
enabled already in Fedora.
However, you remind me of an interesting case: kdump and CMA
reservations
We would be in trouble if we were to automatically create big CMA
regions in the kdump kernel (where we have limited memory), either from
the kernel, like with CMA_SIZE_MBYTES, or via cmdline, like "cmd=2G".
While often such allocations attempts will fail and still allow the
kdump kernel to boot, there can be cases where it will "just work" and
kdump itself might later because it doesn't have sufficient memory
available.
Fortunately, on x86-64 we we have CMA_SIZE_MBYTES set to 0 MiB and our
kdump kernel won't be booted with any "cma=", "hugetlb_cma="
parameters
that might have been specified for the !kdump kernel. So there, we seem
to be fine.
On s390x, we reserve as default a CMA region with 4 MiB. On ppc64 with
HV support, we reserve as default a CMA region with 5% of the
memblock_phys_mem_size() for KVM use; We might want to disable the
latter via is_kdump_kernel() upstream.