Messages in this thread | | | Date | Thu, 31 Aug 2023 16:18:48 +0200 | Subject | Re: [RFC PATCH] Introduce persistent memory pool | From | Paolo Bonzini <> |
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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
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