On 8/26/23 22:04, Greg Kroah-Hartman wrote:
Yeah, I guess the "ABI" word in misleading here, especially the first
letter. I mean something else: the old kernel/new kernel.
This persistent memory pool (its metadata) is supposed to be passed
across kexec with the data. That is probably the main difference in
comparison to pmem or cma.
Since the header can change its format between kernels, there should be
a way to identify it.
Ah. Hah, that's crazy, and it's never going to work, you need to just
test the version of the kernel that the image was created for (you have
that in the kernel already) and verify that it is the same before
loading the new one.
That way you never have to worry about any "version number", it's just
the kernel specific version number instead.
Checking the version of the kernel is not enough because you want to
support kexec to a newer kernel.
I agree though that a version number is not needed. In the end this is
just like a filesystem and you'd better keep it backwards compatible.
If you think you might need an extra field in the header, you have to
leave some padding and add a "flags" field that right now is always
zero. Or something like that.
Paolo
