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Thu, 10 Apr 2025 20:48:06 -0700 (PDT) Date: Thu, 10 Apr 2025 20:47:48 -0700 In-Reply-To: <20250320015551.2157511-13-changyuanl@google.com> Mime-Version: 1.0 References: <20250320015551.2157511-13-changyuanl@google.com> X-Mailer: git-send-email 2.49.0.604.gff1f9ca942-goog Message-ID: <20250411034748.1781232-1-changyuanl@google.com> Subject: Re: [PATCH v5 12/16] arm64: add KHO support From: Changyuan Lyu To: changyuanl@google.com Cc: akpm@linux-foundation.org, anthony.yznaga@oracle.com, arnd@arndb.de, ashish.kalra@amd.com, benh@kernel.crashing.org, bp@alien8.de, catalin.marinas@arm.com, corbet@lwn.net, dave.hansen@linux.intel.com, devicetree@vger.kernel.org, dwmw2@infradead.org, ebiederm@xmission.com, graf@amazon.com, hpa@zytor.com, jgowans@amazon.com, kexec@lists.infradead.org, krzk@kernel.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, luto@kernel.org, mark.rutland@arm.com, mingo@redhat.com, pasha.tatashin@soleen.com, pbonzini@redhat.com, peterz@infradead.org, ptyadav@amazon.de, robh+dt@kernel.org, robh@kernel.org, rostedt@goodmis.org, rppt@kernel.org, saravanak@google.com, skinsburskii@linux.microsoft.com, tglx@linutronix.de, thomas.lendacky@amd.com, will@kernel.org, x86@kernel.org Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250410_204807_976940_92A4E9D7 X-CRM114-Status: GOOD ( 16.90 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Mar 19, 2025 at 18:55:47 -0700, Changyuan Lyu wrote: > From: Alexander Graf > [...] > +/** > + * early_init_dt_check_kho - Decode info required for kexec handover from DT > + */ > +static void __init early_init_dt_check_kho(void) > +{ > + unsigned long node = chosen_node_offset; > + u64 kho_start, scratch_start, scratch_size; > + const __be32 *p; > + int l; > + > + if (!IS_ENABLED(CONFIG_KEXEC_HANDOVER) || (long)node < 0) > + return; > + > + p = of_get_flat_dt_prop(node, "linux,kho-fdt", &l); > + if (l != (dt_root_addr_cells + dt_root_size_cells) * sizeof(__be32)) > + return; > + > + kho_start = dt_mem_next_cell(dt_root_addr_cells, &p); > + > + p = of_get_flat_dt_prop(node, "linux,kho-scratch", &l); > + if (l != (dt_root_addr_cells + dt_root_size_cells) * sizeof(__be32)) > + return; > + > + scratch_start = dt_mem_next_cell(dt_root_addr_cells, &p); > + scratch_size = dt_mem_next_cell(dt_root_addr_cells, &p); > + > + kho_populate(kho_start, scratch_start, scratch_size); > +} > [...] > +static int kho_add_chosen(const struct kimage *image, void *fdt, int chosen_node) > +{ > + int ret = 0; > +#ifdef CONFIG_KEXEC_HANDOVER > + phys_addr_t dt_mem = 0; > + phys_addr_t dt_len = 0; > + phys_addr_t scratch_mem = 0; > + phys_addr_t scratch_len = 0; > + > + if (!image->kho.fdt || !image->kho.scratch) > + return 0; > + > + dt_mem = image->kho.fdt->mem; > + dt_len = image->kho.fdt->memsz; > + > + scratch_mem = image->kho.scratch->mem; > + scratch_len = image->kho.scratch->bufsz; > + > + pr_debug("Adding kho metadata to DT"); > + > + ret = fdt_appendprop_addrrange(fdt, 0, chosen_node, "linux,kho-fdt", > + dt_mem, dt_len); > + if (ret) > + return ret; > + > + ret = fdt_appendprop_addrrange(fdt, 0, chosen_node, "linux,kho-scratch", > + scratch_mem, scratch_len); While testing on ARM64 today, I realized that calling "fdt_appendprop_addrrange" here intercedes a bug that prevents consecutive KHO-enabled kexecs. Suppose we do KHO kexec from kernel 1 to kernel 2 and then from kernel 2 to kernel 3. The firmware DT got by kernel 2 from kernel 1 already has "linux,kho-fdt" and "linux,kho-scratch" in the "chosen" node. And when KHO kexec-ing to kernel 3 from kernel 2, kernel 2 will __append__ the its KHO FDT address to the "linux,kho-fdt". Thus the "linux,kho-fdt" received by kernel 3 contains 2 address ranges. Kernel 3 would fail at early_init_dt_check_kho() above. I will fix this bug in v6. > + > +#endif /* CONFIG_KEXEC_HANDOVER */ > + return ret; > +} > [...] Best, Changyuan