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Mon, 24 Mar 2025 11:40:54 -0700 (PDT) MIME-Version: 1.0 References: <20250320015551.2157511-1-changyuanl@google.com> <20250320015551.2157511-8-changyuanl@google.com> In-Reply-To: <20250320015551.2157511-8-changyuanl@google.com> From: Frank van der Linden Date: Mon, 24 Mar 2025 11:40:43 -0700 X-Gm-Features: AQ5f1JqgK3t9nzg4mdWiXWpH_sA43D2BNXiBuTZpvx6PAjAQCpPGjdYAtW64c_s Message-ID: Subject: Re: [PATCH v5 07/16] kexec: add Kexec HandOver (KHO) generation helpers To: Changyuan Lyu Cc: linux-kernel@vger.kernel.org, graf@amazon.com, akpm@linux-foundation.org, luto@kernel.org, anthony.yznaga@oracle.com, arnd@arndb.de, ashish.kalra@amd.com, benh@kernel.crashing.org, bp@alien8.de, catalin.marinas@arm.com, dave.hansen@linux.intel.com, dwmw2@infradead.org, ebiederm@xmission.com, mingo@redhat.com, jgowans@amazon.com, corbet@lwn.net, krzk@kernel.org, rppt@kernel.org, mark.rutland@arm.com, pbonzini@redhat.com, pasha.tatashin@soleen.com, hpa@zytor.com, peterz@infradead.org, ptyadav@amazon.de, robh+dt@kernel.org, robh@kernel.org, saravanak@google.com, skinsburskii@linux.microsoft.com, rostedt@goodmis.org, tglx@linutronix.de, thomas.lendacky@amd.com, usama.arif@bytedance.com, will@kernel.org, devicetree@vger.kernel.org, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam01 X-Stat-Signature: qwnyueof7ahu64ym7x7mneo3hfjwi1h4 X-Rspam-User: X-Rspamd-Queue-Id: D756C4001D X-HE-Tag: 1742841655-765 X-HE-Meta: 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 NGPzGJhx xMkkyRQhcgZ+mr63xnXlFt+BXxI4Kls9l3ouv6X6JLH7zJIPSYknf9XvS/omA+ZqTU0WeoaUZVmYBGDmioPcernqpKc3OTM/Gp0932C4Qkxtjg3eVVpXWuKW1/kfp3jIykBobT1cDt/55bUk0XjKT38CYlUGN9WWWHZCG2p7PdYD1vlc0Q4N9FxVXYRZojb7gOxPkES5Ooli/5jlOSubTOL0++0HrhsIqms/mG4g/kMG5SFMaNivRHOrq7lHMU3dkKDRoG26QknuO5YtQ2wB4bEL7PR6J5uCzGchUYAYQ14FxHrST32zQRR/xYRkWduXbWyis4R+OUEci9CO0yKsP81pjAg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000011, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Mar 19, 2025 at 6:56=E2=80=AFPM Changyuan Lyu wrote: > > From: Alexander Graf > > 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 > Co-developed-by: Pratyush Yadav > Signed-off-by: Pratyush Yadav > Co-developed-by: Mike Rapoport (Microsoft) > Signed-off-by: Mike Rapoport (Microsoft) > Co-developed-by: Changyuan Lyu > Signed-off-by: Changyuan Lyu > --- > 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 > #include > #include > +#include > #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, b= ut > + * 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