On Sun, Feb 09, 2025 at 11:29:41AM +0100, Krzysztof Kozlowski wrote: > On 06/02/2025 14:27, Mike Rapoport wrote: > > From: "Mike Rapoport (Microsoft)" <rppt@xxxxxxxxxx> > > > > We introduced KHO into Linux: A framework that allows Linux to pass > > metadata and memory across kexec from Linux to Linux. KHO reuses fdt > > as file format and shares a lot of the same properties of firmware-to- > > Linux boot formats: It needs a stable, documented ABI that allows for > > forward and backward compatibility as well as versioning. > > Please use subject prefixes matching the subsystem. You can get them for > example with `git log --oneline -- DIRECTORY_OR_FILE` on the directory > your patch is touching. For bindings, the preferred subjects are > explained here: > https://www.kernel.org/doc/html/latest/devicetree/bindings/submitting-patches.html#i-for-patch-submitters These are not devicetree binding for communicating data from firmware to the kernel. These bindings are specific to KHO which is perfectly reflected by the subject. Just a brief reminder from v2 discussion: (https://lore.kernel.org/linux-mm/20231222193607.15474-1-graf@xxxxxxxxxx/) "For quick reference: KHO is a new mechanism this patch set introduces which allows Linux to pass arbitrary memory and metadata between kernels on kexec. I'm reusing FDTs to implement the hand over protocol, as Linux-to-Linux boot communication holds very similar properties to firmware-to-Linux boot communication. So this binding is not about hardware; it's about preserving Linux subsystem state across kexec. For more details, please refer to the KHO documentation which is part of patch 7 of this patch set: https://lore.kernel.org/lkml/20231222195144.24532-2-graf@xxxxxxxxxx/"; and "This is our own data structure for KHO that just happens to again contain a DT structure. The reason is simple: I want a unified, versioned, introspectable data format that is cross platform so you don't need to touch every architecture specific boot passing logic every time you want to add a tiny piece of data." > > As first user of KHO, we introduced memblock which can now preserve > > memory ranges reserved with reserve_mem command line options contents > > across kexec, so you can use the post-kexec kernel to read traces from > > the pre-kexec kernel. > > > > This patch adds memblock schemas similar to "device" device tree ones to > > a new kho bindings directory. This allows us to force contributors to > > document the data that moves across KHO kexecs and catch breaking change > > during review. > > > > Co-developed-by: Alexander Graf <graf@xxxxxxxxxx> > > Signed-off-by: Alexander Graf <graf@xxxxxxxxxx> > > Signed-off-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx> > > --- > > .../kho/bindings/memblock/reserve_mem.yaml | 41 ++++++++++++++++++ > > .../bindings/memblock/reserve_mem_map.yaml | 42 +++++++++++++++++++ > > 2 files changed, 83 insertions(+) > > create mode 100644 Documentation/kho/bindings/memblock/reserve_mem.yaml > > create mode 100644 Documentation/kho/bindings/memblock/reserve_mem_map.yaml > > > > diff --git a/Documentation/kho/bindings/memblock/reserve_mem.yaml b/Documentation/kho/bindings/memblock/reserve_mem.yaml > > new file mode 100644 > > index 000000000000..7b01791b10b3 > > --- /dev/null > > +++ b/Documentation/kho/bindings/memblock/reserve_mem.yaml > > @@ -0,0 +1,41 @@ > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) > > +%YAML 1.2 > > +--- > > +$id: http://devicetree.org/schemas/memblock/reserve_mem.yaml# > > +$schema: http://devicetree.org/meta-schemas/core.yaml# > > + > > +title: Memblock reserved memory > > + > > +maintainers: > > + - Mike Rapoport <rppt@xxxxxxxxxx> > > + > > +description: | > > + Memblock can serialize its current memory reservations created with > > + reserve_mem command line option across kexec through KHO. > > + The post-KHO kernel can then consume these reservations and they are > > + guaranteed to have the same physical address. > > + > > +examples: > > + - | > > + reserve_mem { > > Again, do not introduce own coding style. > > I don't understand why do you need this in the first place. There is > already reserved-memory block. Because these regions are not "... designed for the special usage by various device drivers" and should not be exclude by the operating system from normal usage. > Best regards, > Krzysztof -- Sincerely yours, Mike.
