On Wed, Mar 19, 2025 at 6:56 PM Changyuan Lyu <changyu...@google.com> wrote: > > From: Alexander Graf <g...@amazon.com> > > Add the core infrastructure to generate Kexec HandOver metadata. Kexec > HandOver is a mechanism that allows Linux to preserve state - arbitrary > properties as well as memory locations - across kexec. > > It does so using 2 concepts: > > 1) State Tree - Every KHO kexec carries a state tree that describes the > state of the system. The state tree is represented as hash-tables. > Device drivers can add/remove their data into/from the state tree at > system runtime. On kexec, the tree is converted to FDT (flattened > device tree). > > 2) Scratch Regions - CMA regions that we allocate in the first kernel. > CMA gives us the guarantee that no handover pages land in those > regions, because handover pages must be at a static physical memory > location. We use these regions as the place to load future kexec > images so that they won't collide with any handover data. > > Signed-off-by: Alexander Graf <g...@amazon.com> > Co-developed-by: Pratyush Yadav <ptya...@amazon.de> > Signed-off-by: Pratyush Yadav <ptya...@amazon.de> > Co-developed-by: Mike Rapoport (Microsoft) <r...@kernel.org> > Signed-off-by: Mike Rapoport (Microsoft) <r...@kernel.org> > Co-developed-by: Changyuan Lyu <changyu...@google.com> > Signed-off-by: Changyuan Lyu <changyu...@google.com> > --- > MAINTAINERS | 2 +- > include/linux/kexec_handover.h | 109 +++++ > kernel/Makefile | 1 + > kernel/kexec_handover.c | 865 +++++++++++++++++++++++++++++++++ > mm/mm_init.c | 8 + > 5 files changed, 984 insertions(+), 1 deletion(-) > create mode 100644 include/linux/kexec_handover.h > create mode 100644 kernel/kexec_handover.c [...] > diff --git a/mm/mm_init.c b/mm/mm_init.c > index 04441c258b05..757659b7a26b 100644 > --- a/mm/mm_init.c > +++ b/mm/mm_init.c > @@ -30,6 +30,7 @@ > #include <linux/crash_dump.h> > #include <linux/execmem.h> > #include <linux/vmstat.h> > +#include <linux/kexec_handover.h> > #include "internal.h" > #include "slab.h" > #include "shuffle.h" > @@ -2661,6 +2662,13 @@ void __init mm_core_init(void) > report_meminit(); > kmsan_init_shadow(); > stack_depot_early_init(); > + > + /* > + * KHO memory setup must happen while memblock is still active, but > + * as close as possible to buddy initialization > + */ > + kho_memory_init(); > + > mem_init(); > kmem_cache_init(); > /*
Thanks for the work on this. Obviously it needs to happen while memblock is still active - but why as close as possible to buddy initialization? Ordering is always a sticky issue when it comes to doing things during boot, of course. In this case, I can see scenarios where code that runs a little earlier may want to use some preserved memory. The current requirement in the patch set seems to be "after sparse/page init", but I'm not sure why it needs to be as close as possibly to buddy init. - Frank
