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Thu, 2 Jul 2020 11:48:01 +0000 (UTC) Date: Thu, 2 Jul 2020 19:47:58 +0800 From: Dave Young To: Hari Bathini Subject: Re: [PATCH 01/11] kexec_file: allow archs to handle special regions while locating memory hole Message-ID: <20200702114758.GA21026@dhcp-128-65.nay.redhat.com> References: <159319825403.16351.7253978047621755765.stgit@hbathini.in.ibm.com> <159319828304.16351.6990340111766605842.stgit@hbathini.in.ibm.com> <20200629133933.0787f562@ezekiel.suse.cz> <7981ae61-26c6-000c-9ee4-382dab3eecab@linux.ibm.com> <20200701074659.GA3878@dhcp-128-65.nay.redhat.com> <0e145e84-a6cf-4da3-1a1a-331a7e1ac1fa@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0e145e84-a6cf-4da3-1a1a-331a7e1ac1fa@linux.ibm.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Pingfan Liu , Petr Tesarik , Kexec-ml , Mahesh J Salgaonkar , Mimi Zohar , lkml , linuxppc-dev , Sourabh Jain , Vivek Goyal , Andrew Morton , Thiago Jung Bauermann , Eric Biederman Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 07/02/20 at 12:01am, Hari Bathini wrote: > > > On 01/07/20 1:16 pm, Dave Young wrote: > > On 06/29/20 at 05:26pm, Hari Bathini wrote: > >> Hi Petr, > >> > >> On 29/06/20 5:09 pm, Petr Tesarik wrote: > >>> Hi Hari, > >>> > >>> is there any good reason to add two more functions with a very similar > >>> name to an existing function? AFAICS all you need is a way to call a > >>> PPC64-specific function from within kexec_add_buffer (PATCH 4/11), so > >>> you could add something like this: > >>> > >>> int __weak arch_kexec_locate_mem_hole(struct kexec_buf *kbuf) > >>> { > >>> return 0; > >>> } > >>> > >>> Call this function from kexec_add_buffer where appropriate and then > >>> override it for PPC64 (it roughly corresponds to your > >>> kexec_locate_mem_hole_ppc64() from PATCH 4/11). > >>> > >>> FWIW it would make it easier for me to follow the resulting code. > >> > >> Right, Petr. > >> > >> I was trying out a few things before I ended up with what I sent here. > >> Bu yeah.. I did realize arch_kexec_locate_mem_hole() would have been better > >> after sending out v1. Will take care of that in v2. > > > > Another way is use arch private function to locate mem hole, then set > > kbuf->mem, and then call kexec_add_buf, it will skip the common locate > > hole function. > > Dave, I did think about it. But there are a couple of places this can get > tricky. One is ima_add_kexec_buffer() and the other is kexec_elf_load(). > These call sites could be updated to set kbuf->mem before kexec_add_buffer(). > But the current approach seemed like the better option for it creates a > single point of control in setting up segment buffers and also, makes adding > any new segments simpler, arch-specific segments or otherwise. > Ok, thanks for the explanation.