From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5] helo=mx0a-001b2d01.pphosted.com) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jwC1R-0001vG-Gw for kexec@lists.infradead.org; Thu, 16 Jul 2020 22:06:34 +0000 References: <159466074408.24747.10036072269371204890.stgit@hbathini.in.ibm.com> <159466096898.24747.16701009925943468066.stgit@hbathini.in.ibm.com> <87y2nk8cjq.fsf@morokweng.localdomain> From: Thiago Jung Bauermann Subject: Re: [PATCH v3 09/12] ppc64/kexec_file: setup backup region for kdump kernel In-reply-to: Date: Thu, 16 Jul 2020 19:06:20 -0300 Message-ID: <874kq7cdyb.fsf@morokweng.localdomain> MIME-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Hari Bathini Cc: kernel test robot , Pingfan Liu , Petr Tesarik , Nayna Jain , Kexec-ml , Mahesh J Salgaonkar , Mimi Zohar , lkml , linuxppc-dev , Sourabh Jain , Andrew Morton , Dave Young , Vivek Goyal , Eric Biederman Hari Bathini writes: > On 16/07/20 7:08 am, Thiago Jung Bauermann wrote: >> >> Hari Bathini writes: >> >>> @@ -968,7 +1040,7 @@ int setup_new_fdt_ppc64(const struct kimage *image, void *fdt, >>> >>> /* >>> * Restrict memory usage for kdump kernel by setting up >>> - * usable memory ranges. >>> + * usable memory ranges and memory reserve map. >>> */ >>> if (image->type == KEXEC_TYPE_CRASH) { >>> ret = get_usable_memory_ranges(&umem); >>> @@ -980,6 +1052,24 @@ int setup_new_fdt_ppc64(const struct kimage *image, void *fdt, >>> pr_err("Error setting up usable-memory property for kdump kernel\n"); >>> goto out; >>> } >>> + >>> + ret = fdt_add_mem_rsv(fdt, BACKUP_SRC_START + BACKUP_SRC_SIZE, >>> + crashk_res.start - BACKUP_SRC_SIZE); >> >> I believe this answers my question from the other email about how the >> crashkernel is prevented from stomping in the crashed kernel's memory, >> right? I needed to think for a bit to understand what the above >> reservation was protecting. I think it's worth adding a comment. > > Right. The reason to add it in the first place is, prom presses the panic button if > it can't find low memory. Marking it reserved seems to keep it quiet though. so.. > > Will add comment mentioning that.. Ah, makes sense. Thanks for the explanation. >>> +void purgatory(void) >>> +{ >>> + void *dest, *src; >>> + >>> + src = (void *)BACKUP_SRC_START; >>> + if (backup_start) { >>> + dest = (void *)backup_start; >>> + __memcpy(dest, src, BACKUP_SRC_SIZE); >>> + } >>> +} >> >> In general I'm in favor of using C code over assembly, but having to >> bring in that relocation support just for the above makes me wonder if >> it's worth it in this case. > > I am planning to build on purgatory later with "I'm in purgatory" print support > for pseries at least and also, sha256 digest check. Ok. In that case, my preference would be to convert both the powerpc and x86 purgatories to PIE since this greatly reduces the types of relocations that are emitted, but better ask Dave Young what he thinks before going down that route. -- Thiago Jung Bauermann IBM Linux Technology Center _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec