linux-kernel - Re: [PATCH v5 00/16] kexec: introduce Kexec HandOver (KHO)

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Message-ID: <CA+CK2bDtBk=49hbz+C=fDswz_Nbtj8kVjsY-pTsmBt+O8YPLmg@mail.gmail.com>
Date: Tue, 25 Mar 2025 10:19:53 -0400
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: Changyuan Lyu <changyuanl@...gle.com>
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Subject: Re: [PATCH v5 00/16] kexec: introduce Kexec HandOver (KHO)

> To use the code, please boot the kernel with the "kho=on" command line
> parameter.
> KHO will automatically create scratch regions. If you want to set the
> scratch size explicitly you can use "kho_scratch=" command line parameter.
> For instance, "kho_scratch=16M,512M,256M" will reserve a 16 MiB low
> memory scratch area, a 512 MiB global scratch region, and 256 MiB
> per NUMA node scratch regions on boot.

kho_scratch= is confusing. It should be renamed to what this memory
actually represents, which is memory that cannot be preserved by KHO.

I suggest renaming all references to "scratch" and this parameter to:

kho_nopersistent= or kho_nopreserve=

This way, we can also add checks that early allocations done by the
kernel in this memory do not get preserved. We can also add checks to
ensure that scarce low DMA memory does not get preserved across
reboots, and we avoid adding fragmentation to that region.

Pasha