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AJvYcCUqBAjcGICc3oEuHbXJoq486oqP1gtxXfBovBXkX2xREYVn4ahQkr+T3b7mDCxOfbK/7Nj7CCG8dQ==@kvack.org X-Gm-Message-State: AOJu0YwinRglCojOQ52+qkpRL9bj5oEIzB5M5RNR5pcQi79IoVUG9Z58 /Q9OdP2uHO6WALBJnUSzHWq8CpoxAkrG9COzBPE8Xsavejk3LfNJ44sI91TYaF5yCEXWDra7SXZ MZrBAxWi83REfYfDyyhhEC7QnImo= X-Gm-Gg: ASbGnctXALVxWpJ/cbofxyZ09UH001dz7fzu/fKSYdpHMRtFkhk813cRVqIw9J9I1ua viwOYf8gR1pKgHzKnwKNPhfZ/7/TI8KQBnuMeFIcRrQcSMfYarQLAeLcLDkbWBSmykko+xBfPW5 B9D3kzG5oFHoCmhWYDwLYVk/rT+EXyhg== X-Google-Smtp-Source: AGHT+IHbvBsh6V0fXstr8+BOoSkHjjWgUMnEaXVoAFyg/1U+OLW9gAoZ0JTlsqAOxqlsdld7G6QKRI/njRDoksoZ/U0= X-Received: by 2002:a05:6102:8086:b0:4af:ef82:ce8d with SMTP id ada2fe7eead31-4ba86dc8dc9mr5995609137.0.1739062316419; Sat, 08 Feb 2025 16:51:56 -0800 (PST) MIME-Version: 1.0 References: <20250206132754.2596694-1-rppt@kernel.org> In-Reply-To: <20250206132754.2596694-1-rppt@kernel.org> From: Cong Wang Date: Sat, 8 Feb 2025 16:51:44 -0800 X-Gm-Features: AWEUYZlTa-fKw29GejPO9DLzpee4iJIj63nbPkF2TO1t-8jFRDudad4UpWMOvAI Message-ID: Subject: Re: [PATCH v4 00/14] kexec: introduce Kexec HandOver (KHO) To: Mike Rapoport Cc: linux-kernel@vger.kernel.org, Alexander Graf , Andrew Morton , Andy Lutomirski , Anthony Yznaga , Arnd Bergmann , Ashish Kalra , Benjamin Herrenschmidt , Borislav Petkov , Catalin Marinas , Dave Hansen , David Woodhouse , Eric Biederman , Ingo Molnar , James Gowans , Jonathan Corbet , Krzysztof Kozlowski , Mark Rutland , Paolo Bonzini , Pasha Tatashin , "H. Peter Anvin" , Peter Zijlstra , Pratyush Yadav , Rob Herring , Rob Herring , Saravana Kannan , Stanislav Kinsburskii , Steven Rostedt , Thomas Gleixner , Tom Lendacky , Usama Arif , Will Deacon , 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-Stat-Signature: nkiihhdmqhqs8tokkhzputfbr6thhwiq X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 78A2B40006 X-Rspam-User: X-HE-Tag: 1739062317-827507 X-HE-Meta: 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 65pE6Vd4 JcEQ9/XarujBH2lLGm4I2KuQDzjBUef4/7BkxdTjHMEur+oI5nuumX5a/zb3cVxxgqgZU8mvX/9G/1FCLiKbsP5ZtF0E1gdSEh/ELCOKcgrO8h0QTm5IszH/YHLyI77EQOMzkMEC1neTaYLOzbt/aKWHFdQCQIt6cnlWIeCUDWg/AF0WpOW4dDKpbzQUynAyISozu/fJAjq4hg3ZOwSGn33Zq9y6GBkpUfGr58bgKWTTRYwVK3DXx2RbKAbO0AjECLnxBzRjmn9dtV8v0FBUBcBZhoEU+rpmcX1HuSj7WS7Bry4vCx6sm43WncqKvNRUz1Stn9miP0HldK8fM9KuCCnnjKNDIr5p/qZUMXNP9k1uXfeDqyVrcSwYhtDdVYVYnBOZULE2Z3pRE4cjJGoT9lsuyXMXBp52DyFiaB08NhrgcZRJtcRdHNyV9PFlcbba9ZoAk X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Mike, On Thu, Feb 6, 2025 at 5:28=E2=80=AFAM Mike Rapoport wrot= e: > We introduce a metadata file that the kernels pass between each other. Ho= w > they pass it is architecture specific. The file's format is a Flattened > Device Tree (fdt) which has a generator and parser already included in > Linux. When the root user enables KHO through /sys/kernel/kho/active, the > kernel invokes callbacks to every driver that supports KHO to serialize > its state. When the actual kexec happens, the fdt is part of the image > set that we boot into. In addition, we keep a "scratch regions" available > for kexec: A physically contiguous memory regions that is guaranteed to > not have any memory that KHO would preserve. The new kernel bootstraps > itself using the scratch regions and sets all handed over memory as in us= e. > When drivers initialize that support KHO, they introspect the fdt and > recover their state from it. This includes memory reservations, where the > driver can either discard or claim reservations. I have gone through your entire patchset, if you could provide an example of a specific driver that supports KHO it would help a lot for people to understand and more importantly help driver developers to adopt. Even with a simulated driver, e.g. netdevsim, it would be greatly helpful. Thanks.