linux-kernel - Re: [PATCH v4 00/14] kexec: introduce Kexec HandOver (KHO)

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Message-ID: <Z6a1kxR2GlQoepgI@MiWiFi-R3L-srv>
Date: Sat, 8 Feb 2025 09:38:27 +0800
From: Baoquan He <bhe@...hat.com>
To: Pasha Tatashin <pasha.tatashin@...een.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Mike Rapoport <rppt@...nel.org>, linux-kernel@...r.kernel.org,
	Alexander Graf <graf@...zon.com>, Andy Lutomirski <luto@...nel.org>,
	Anthony Yznaga <anthony.yznaga@...cle.com>,
	Arnd Bergmann <arnd@...db.de>, Ashish Kalra <ashish.kalra@....com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Borislav Petkov <bp@...en8.de>,
	Catalin Marinas <catalin.marinas@....com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Eric Biederman <ebiederm@...ssion.com>,
	Ingo Molnar <mingo@...hat.com>, James Gowans <jgowans@...zon.com>,
	Jonathan Corbet <corbet@....net>,
	Krzysztof Kozlowski <krzk@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Pratyush Yadav <ptyadav@...zon.de>,
	Rob Herring <robh+dt@...nel.org>, Rob Herring <robh@...nel.org>,
	Saravana Kannan <saravanak@...gle.com>,
	Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tom Lendacky <thomas.lendacky@....com>,
	Usama Arif <usama.arif@...edance.com>,
	Will Deacon <will@...nel.org>, devicetree@...r.kernel.org,
	kexec@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
	linux-doc@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
	changyuanl@...gle.com
Subject: Re: [PATCH v4 00/14] kexec: introduce Kexec HandOver (KHO)

On 02/06/25 at 08:28pm, Pasha Tatashin wrote:
> On Thu, Feb 6, 2025 at 7:29 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
> >
> > On Thu,  6 Feb 2025 15:27:40 +0200 Mike Rapoport <rppt@...nel.org> wrote:
> >
> > > This a next version of Alex's "kexec: Allow preservation of ftrace buffers"
> > > series (https://lore.kernel.org/all/20240117144704.602-1-graf@amazon.com),
> > > just to make things simpler instead of ftrace we decided to preserve
> > > "reserve_mem" regions.
> > >
> > > The patches are also available in git:
> > > https://git.kernel.org/rppt/h/kho/v4
> > >
> > >
> > > Kexec today considers itself purely a boot loader: When we enter the new
> > > kernel, any state the previous kernel left behind is irrelevant and the
> > > new kernel reinitializes the system.
> >
> > I tossed this into mm.git for some testing and exposure.
> >
> > What merge path are you anticipating?
> >
> > Review activity seems pretty thin thus far?
> 
> KHO is going to be discussed at the upcoming lsfmm, we are also
> planning to send v5 of this patch series (discussed with Mike
> Rapoport) in a couple of weeks. It will include enhancements needed
> for the hypervisor live update scenario:

So is this V4 still a RFC if v5 will be sent by plan? Should we hold the
reviewing until v5? Or this series is a infrustructure building, v5 will
add more details as you listed as below. I am a little confused.

> 
> 1. Allow nodes to be added to the KHO tree at any time
> 2. Remove "activate" (I will also send a live update framework that
> provides the activate functionality).
> 3. Allow serialization during shutdown.
> 4. Decouple KHO from kexec_file_load(), as kexec_file_load() should
> not be used during live update blackout time.
> 5. Enable multithreaded serialization by using hash-table as an
> intermediate step before conversion to FDT.