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b=Q42qAzt7wO+OFo6NAoDwEE1MDA4cRI3i/Jy/Qfuq0/wpgUimD8W/1lqVrecho7Kou WabJVL20LNw0REudcaOdeeb+T4PExYxgh/OrdVdLoMnod1bxNeVKjrL//TlXvOHr0x uQHhG+p4fnpTaLGkuKPKt0lF/tSHSWpnsQUDz0yCQ6i6NLviOmP5AwbmF7hifJoymO a/dj9wKcgweN0UsrgQ7dl0KBXGcJZvkPwCfEnGRPKB6PFdnVB0tUKh1QamLTWNKEsV B4ughp0yGBPUNdq905IDJDtq0MYVx2RWuc4ruH3JiWRRurjm5VB3sZIQTW+1rluU58 6VzR/lgTAk56Q== From: sashiko-bot@kernel.org Subject: Re: [PATCH v5 17/17] arm64: crash: Add crash hotplug support Reply-To: sashiko-reviews@lists.linux.dev To: tglx@kernel.org, ritesh.list@gmail.com, mark.rutland@arm.com, chao.gao@intel.com, kas@kernel.org, linuxppc-dev@lists.ozlabs.org, yeoreum.yun@arm.com, x86@kernel.org, baoquan.he@linux.dev, hbathini@linux.ibm.com, sourabhjain@linux.ibm.com, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, jbouron@amazon.com, dave.hansen@linux.intel.com, rafael@kernel.org, coxu@redhat.com, akpm@linux-foundation.org, gshan@redhat.com, vishal.l.verma@intel.com, ruirui.yang@linux.dev, seanjc@google.com, bgwin@google.com, "Jinjie Ruan" , chenhuacai@kernel.org, pasha.tatashin@soleen.com, kees@kernel.org, me@linux.beauty, npiggin@gmail.com, maddy@linux.ibm.com, ruanjinjie@huawei.com, thuth@redhat.com, graf@amazon.com, palmer@rivosinc.com, chleroy@kernel.org, guodongtai@kylinos.cn, zhangtianyang@loongson.cn, eric.devolder@oracle.com, catalin.marinas@arm.com, leitao@debian.org, driver-core@lists.linux.dev, piliu@redhat.com, kernel@xen0n.name, dakr@kernel.org, pratyush@kernel.org, sshegde@linux.ibm.com, tangyouling@kylinos.cn, adityag@linux.ibm.com, rppt@kernel.org, mclapinski@google.com, takahiro.akashi@linaro.org, linux-arm-kernel@lists.infradead.org, will@kernel.org, ardb@kernel.org, gregkh@linuxfoundation.org, lizhengyu3@huawei.com, linux-mm@kvack.org, james.morse@arm.com, linux-fsdevel@vger.kernel.org, mpe@ellerman.id.au, mingo@redhat.com, bp@alien8.de, blum@kernel.org, robh@kernel.org, hpa@zytor.com, liukexin@kylinos.cn, maqianga@uniontech.com Cc: kexec@lists.infradead.org In-Reply-To: <20260918100442.3841135-18-ruanjinjie@huawei.com> References: <20260918100442.3841135-1-ruanjinjie@huawei.com> <20260918100442.3841135-18-ruanjinjie@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Fri, 18 Sep 2026 10:36:56 +0000 Message-Id: <20260918103657.0CC341F000FF@smtp.kernel.org> X-Stat-Signature: iqf7n9rpnugmcck5w9x8f448ijwcbcee X-Rspam-User: X-Rspamd-Queue-Id: B6566140003 X-Rspamd-Server: rspam03 X-HE-Tag: 1789727820-145839 X-HE-Meta: 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 4Yn6ZR83 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Thank you for your contribution! Sashiko AI review found 1 potential issue(= s) to consider: - [High] kexec: arch_crash_get_elfcorehdr_size() exports undersized buffer = when MEMORY_HOTPLUG is disabled -- commit fd293f9cfd1a12554d9352f4ad58fc9f85721fa3 Author: Jinjie Ruan arm64: crash: Add crash hotplug support This commit introduces kernel mechanisms to update only the elfcorehdr on memory hotplug events for arm64. It adds ARCH_SUPPORTS_CRASH_HOTPLUG=20 and implements arch-specific functions to handle memory hotplug, avoiding full kdump image reloads from userspace. Link: https://lore.kernel.org/all/20240529133446.28446-1-Jonathan.Cameron@h= uawei.com/ > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index b5a51b0ef9440..96de2660b1cbb 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -1720,6 +1720,9 @@ config ARCH_DEFAULT_CRASH_DUMP > config ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION > def_bool CRASH_RESERVE > =20 > +config ARCH_SUPPORTS_CRASH_HOTPLUG > + def_bool y > + [Severity: High] Does unconditionally enabling ARCH_SUPPORTS_CRASH_HOTPLUG here expose an undersized buffer to userspace when CONFIG_MEMORY_HOTPLUG is disabled? Since CONFIG_HOTPLUG_CPU natively selects CONFIG_CRASH_HOTPLUG on architectures that support it, having this default to 'y' allows CRASH_HOTPLUG to be active even without MEMORY_HOTPLUG. This leads to the size calculation issue below. [ ... ] > diff --git a/arch/arm64/kernel/crash.c b/arch/arm64/kernel/crash.c > new file mode 100644 > index 0000000000000..08dc9b952498e > --- /dev/null > +++ b/arch/arm64/kernel/crash.c [ ... ] > +unsigned int arch_crash_get_elfcorehdr_size(void) > +{ > + unsigned long phdr_cnt; > + > + /* A program header for possible CPUs, vmcoreinfo and kernel_map */ > + phdr_cnt =3D 2 + num_possible_cpus(); > + if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) > + phdr_cnt +=3D CONFIG_CRASH_MAX_MEMORY_RANGES; > + [Severity: High] Is this calculation missing the static memory ranges when CONFIG_MEMORY_HOTPLUG is disabled? If compiled with CONFIG_HOTPLUG_CPU=3Dy (which natively selects CONFIG_CRASH_HOTPLUG) and CONFIG_MEMORY_HOTPLUG=3Dn, phdr_cnt is computed as exactly 2 + num_possible_cpus(). This does not account for the mandatory memblock ranges from arch_get_system_nr_ranges().=20 Unlike x86 or powerpc which might survive this due to heavily padded CONFIG_NR_CPUS_DEFAULT values, arm64's precise num_possible_cpus() leaves zero headroom. As a result, the exported maximum elfcorehdr size is strictly smaller than the required size to hold static memory ranges, and any attempt to arm kdump (kexec -p) will fail because kexec-tools cannot load the crash kernel into the undersized segment. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260918100442.3841= 135-1-ruanjinjie@huawei.com?part=3D17