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AJvYcCUxriF7DNgNChOBwLpI0/uS6McvOWAyLnCXX5xDJaAN0gHBQYDn1TsLU7rjSL7G2x74JO9kMIDUFg==@kvack.org X-Gm-Message-State: AOJu0YykyZc7811W1GXHA5Awa7KXGHIQVJDvDt0T86VWi/ISqBzXRAWe 8JVE0VV45wHRPgsk7R9n7FuJ9cgQqjDETOouqqW81rLpGNwYB4kU2LmFjkPC1hTtKxPNMRYfOWg h4eX6INSBcm3UOwQQWAdZVOrt0N5+/nz64kCKlQ== X-Gm-Gg: ASbGncsAHv4Ie0724uqIPdm3TQf4IigPC7Zgh+U0DjXIj6nq2nf1SnMAJqYCOkfo71P Gyr2p3n6yfm2U61xs/Yos9UzF+j3jvcIw/VaMQdB6w4FOe6il56yUX8k8dXJSoxRnCSBTGvM5aq abWnPxOxZLHe4qnzBvXLO7u5SoKt6j1GODIJk= X-Google-Smtp-Source: AGHT+IGstsIg4qTmJ5YmWZYDNChDQ3+AV2nMWCj2a+cFs02lJM90kE8eqj7HIwLM8JIykyDhXLdef0fVOQCXvqByXHY= X-Received: by 2002:a05:622a:550f:b0:472:bbb:1bab with SMTP id d75a77b69052e-4771dd88e91mr196322501cf.24.1742844440714; Mon, 24 Mar 2025 12:27:20 -0700 (PDT) MIME-Version: 1.0 References: <20250320015551.2157511-1-changyuanl@google.com> <20250320015551.2157511-12-changyuanl@google.com> In-Reply-To: From: Pasha Tatashin Date: Mon, 24 Mar 2025 15:26:43 -0400 X-Gm-Features: AQ5f1JrjPincvTv7ELB8J7T2hdmnlfkqUUS0uCgm9_GvQ7ohVp8PZ0NaxW7sdEs Message-ID: Subject: Re: [PATCH v5 11/16] kexec: add config option for KHO To: Dave Young Cc: Changyuan Lyu , 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, 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: rspam04 X-Rspamd-Queue-Id: B2885180013 X-Stat-Signature: m7yaor8iaf4q5f4kgzkrgyrbyx5c941d X-Rspam-User: X-HE-Tag: 1742844441-77198 X-HE-Meta: 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 c3zSLm4m WAt2JJBmtaZp8GnHP/4Smlj2C0KoyV0LhLmSbyJOGPY6z0NDxOBHFSFahjhT1XwKIefQmMkAyfCJWdK8bfEYz6AN6DaRsDXfKM+o9guG+HMshuOFeNXLw5svMOyXcd7xKP6nBc5IvyDPGjTft0g+8d6UY4vLuwRo5/IARCcL1qPR4B+fWG7OUvJ/Bror5sYP9slQGFLOCtHrUxTIJQYj9tKPd6539J4S0BHgzTnhyAis0xXoMMM8krjhGPV92Zg/3HLWAlRC4K2Mqqb/fenRxrJfEK0VA4dA5taKax2LNuRmDkcfZs/Q164vK9qusZxWKWSk/WPyIDdy8OVOPuZu0BPlIH7VJzcXsl8zAg49iloogiMEFuEjVisr3mTya+R9c5xENM4t7/EGwX4UkXNu77Vlk5aHXzXiZC6Sv 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: On Mon, Mar 24, 2025 at 12:18=E2=80=AFAM Dave Young wro= te: > > On Thu, 20 Mar 2025 at 23:05, Changyuan Lyu wrote= : > > > > From: Alexander Graf > > > > We have all generic code in place now to support Kexec with KHO. This > > patch adds a config option that depends on architecture support to > > enable KHO support. > > > > Signed-off-by: Alexander Graf > > Co-developed-by: Mike Rapoport (Microsoft) > > Signed-off-by: Mike Rapoport (Microsoft) > > Co-developed-by: Changyuan Lyu > > Signed-off-by: Changyuan Lyu > > --- > > kernel/Kconfig.kexec | 15 +++++++++++++++ > > 1 file changed, 15 insertions(+) > > > > diff --git a/kernel/Kconfig.kexec b/kernel/Kconfig.kexec > > index 4d111f871951..57db99e758a8 100644 > > --- a/kernel/Kconfig.kexec > > +++ b/kernel/Kconfig.kexec > > @@ -95,6 +95,21 @@ config KEXEC_JUMP > > Jump between original kernel and kexeced kernel and invoke > > code in physical address mode via KEXEC > > > > +config KEXEC_HANDOVER > > + bool "kexec handover" > > + depends on ARCH_SUPPORTS_KEXEC_HANDOVER && ARCH_SUPPORTS_KEXEC_= FILE > > + select MEMBLOCK_KHO_SCRATCH > > + select KEXEC_FILE > > + select DEBUG_FS > > + select LIBFDT > > + select CMA > > + select XXHASH > > + help > > + Allow kexec to hand over state across kernels by generating a= nd > > + passing additional metadata to the target kernel. This is use= ful > > + to keep data or state alive across the kexec. For this to wor= k, > > + both source and target kernels need to have this option enabl= ed. > > + > > Have you tested kdump? In my mind there are two issues, one is with > CMA enabled, it could cause kdump crashkernel memory reservation > failures more often due to the fragmented low memory. Secondly, in As I understand cma low memory scratch reservation is needed only to support some legacy pci devices that cannot use the full 64-bit space. If so, I am not sure if KHO needs to be supported on machines with such devices. However, even if we keep it, it should really be small, so I would not expect that to be a problem for crash kernel memory reservation. > kdump kernel dump the crazy scratch memory in vmcore is not very > meaningful. Otherwise I suspect this is not tested under kdump. If > so please disable this option for kdump. The scratch memory will appear as regular CMA in the vmcore. The crash kernel can be kexec loaded only from userland, long after the scratch memory is converted to CMA. Pasha