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Fri, 12 Feb 2021 19:39:49 GMT Received: from b01ledav004.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6C774112062; Fri, 12 Feb 2021 19:39:49 +0000 (GMT) Received: from b01ledav004.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E7AC1112061; Fri, 12 Feb 2021 19:39:41 +0000 (GMT) Received: from manicouagan.localdomain (unknown [9.160.55.153]) by b01ledav004.gho.pok.ibm.com (Postfix) with ESMTPS; Fri, 12 Feb 2021 19:39:41 +0000 (GMT) References: <20210209182200.30606-1-nramas@linux.microsoft.com> <20210209182200.30606-3-nramas@linux.microsoft.com> <87k0reozwh.fsf@manicouagan.localdomain> <8a3aa3d2-2eba-549a-9970-a2b0fe3586c9@linux.microsoft.com> <55685b61-dac0-2f24-f74a-939acf74a4f2@linux.microsoft.com> <11aff288-feaa-8e43-fcda-12bc12fbf4cf@linux.microsoft.com> User-agent: mu4e 1.4.10; emacs 27.1 From: Thiago Jung Bauermann To: Lakshmi Ramasubramanian Subject: Re: [PATCH v17 02/10] of: Add a common kexec FDT setup function In-reply-to: <11aff288-feaa-8e43-fcda-12bc12fbf4cf@linux.microsoft.com> Date: Fri, 12 Feb 2021 16:39:39 -0300 Message-ID: <87im6xulc4.fsf@manicouagan.localdomain> MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369, 18.0.737 definitions=2021-02-12_07:2021-02-12, 2021-02-12 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 clxscore=1015 impostorscore=0 mlxlogscore=999 bulkscore=0 priorityscore=1501 mlxscore=0 adultscore=0 malwarescore=0 suspectscore=0 spamscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102120140 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210212_144014_053672_21176B68 X-CRM114-Status: GOOD ( 24.36 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Benjamin Herrenschmidt , tao.li@vivo.com, Mimi Zohar , Paul Mackerras , vincenzo.frascino@arm.com, Frank Rowand , Sasha Levin , Rob Herring , Michael Ellerman , Masahiro Yamada , James Morris , "AKASHI, Takahiro" , linux-arm-kernel , Catalin Marinas , "Serge E. Hallyn" , devicetree@vger.kernel.org, Pavel Tatashin , Will Deacon , Prakhar Srivastava , Hsin-Yi Wang , Allison Randal , Christophe Leroy , Matthias Brugger , balajib@linux.microsoft.com, dmitry.kasatkin@gmail.com, "linux-kernel@vger.kernel.org" , James Morse , Greg Kroah-Hartman , Joe Perches , linux-integrity@vger.kernel.org, linuxppc-dev Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Lakshmi Ramasubramanian writes: > On 2/12/21 10:24 AM, Rob Herring wrote: >> On Fri, Feb 12, 2021 at 11:19 AM Lakshmi Ramasubramanian >> wrote: >>> >>> On 2/12/21 6:38 AM, Rob Herring wrote: >>>> On Thu, Feb 11, 2021 at 7:17 PM Lakshmi Ramasubramanian >>>> wrote: >>>>> >>>>> On 2/11/21 5:09 PM, Thiago Jung Bauermann wrote: >>>>>> >>>>>> There's actually a complication that I just noticed and needs to be >>>>>> addressed. More below. >>>>>> >>>>> >>>>> <...> >>>>> >>>>>>> + >>>>>>> +/* >>>>>>> + * of_kexec_alloc_and_setup_fdt - Alloc and setup a new Flattened Device Tree >>>>>>> + * >>>>>>> + * @image: kexec image being loaded. >>>>>>> + * @initrd_load_addr: Address where the next initrd will be loaded. >>>>>>> + * @initrd_len: Size of the next initrd, or 0 if there will be none. >>>>>>> + * @cmdline: Command line for the next kernel, or NULL if there will >>>>>>> + * be none. >>>>>>> + * >>>>>>> + * Return: fdt on success, or NULL errno on error. >>>>>>> + */ >>>>>>> +void *of_kexec_alloc_and_setup_fdt(const struct kimage *image, >>>>>>> + unsigned long initrd_load_addr, >>>>>>> + unsigned long initrd_len, >>>>>>> + const char *cmdline) >>>>>>> +{ >>>>>>> + void *fdt; >>>>>>> + int ret, chosen_node; >>>>>>> + const void *prop; >>>>>>> + unsigned long fdt_size; >>>>>>> + >>>>>>> + fdt_size = fdt_totalsize(initial_boot_params) + >>>>>>> + (cmdline ? strlen(cmdline) : 0) + >>>>>>> + FDT_EXTRA_SPACE; >>>>>> >>>>>> Just adding 4 KB to initial_boot_params won't be enough for crash >>>>>> kernels on ppc64. The current powerpc code doubles the size of >>>>>> initial_boot_params (which is normally larger than 4 KB) and even that >>>>>> isn't enough. A patch was added to powerpc/next today which uses a more >>>>>> precise (but arch-specific) formula: >>>>>> >>>>>> https://lore.kernel.org/linuxppc-dev/161243826811.119001.14083048209224609814.stgit@hbathini/ >>>>>> >>>>>> So I believe we need a hook here where architectures can provide their >>>>>> own specific calculation for the size of the fdt. Perhaps a weakly >>>>>> defined function providing a default implementation which an >>>>>> arch-specific file can override (a la arch_kexec_kernel_image_load())? >>>>>> >>>>>> Then the powerpc specific hook would be the kexec_fdt_totalsize_ppc64() >>>>>> function from the patch I linked above. >>>>>> >>>>> >>>>> Do you think it'd better to add "fdt_size" parameter to >>>>> of_kexec_alloc_and_setup_fdt() so that the caller can provide the >>>>> desired FDT buffer size? >>>> >>>> Yes, I guess so. But please define the param as extra size, not total >>>> size. The kernel command line size addition can be in the common code. >>> >>> Will do. Just to clarify - >>> >>> The common code will do: >>> >>> fdt_totalsize(initial_boot_params) + strlen(cmdline) + extra_fdt_size >>> >>> The caller will pass "extra_fdt_size" >>> ARM64 => 4KB >>> PPC64 => fdt_totalsize(initial_boot_params) - which will be updated when >>> the patch Thiago had referred to is merged. >> Yes, I'd leave the 4KB in there by default and arm64 use 0. >> > > Sounds good. > > common: > fdt_totalsize(initial_boot_params) + strlen(cmdline) + 0x1000 + extra > > arm64 => 0 for extra > ppc => fdt_totalsize(initial_boot_params) for extra. Looks good to me. -- Thiago Jung Bauermann IBM Linux Technology Center _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel