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Mar 2023 15:19:22 +0000 Date: Fri, 17 Mar 2023 08:19:20 -0700 From: Dan Williams To: "lizhijian@fujitsu.com" , Dan Williams , "kexec@lists.infradead.org" , "nvdimm@lists.linux.dev" , "linux-mm@kvack.org" CC: Baoquan He , "vgoyal@redhat.com" , "dyoung@redhat.com" , "vishal.l.verma@intel.com" , "dave.jiang@intel.com" , "horms@verge.net.au" , "k-hagio-ab@nec.com" , "akpm@linux-foundation.org" , "Yasunori Gotou (Fujitsu)" , "yangx.jy@fujitsu.com" , "ruansy.fnst@fujitsu.com" Subject: Re: [RFC][nvdimm][crash] pmem memmap dump support Message-ID: <641484f7ef780_a52e2940@dwillia2-mobl3.amr.corp.intel.com.notmuch> References: <3c752fc2-b6a0-2975-ffec-dba3edcf4155@fujitsu.com> <641404ea806dc_a52e2949@dwillia2-mobl3.amr.corp.intel.com.notmuch> <03bf236a-e832-ab81-2b2d-448aea37a2e4@fujitsu.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <03bf236a-e832-ab81-2b2d-448aea37a2e4@fujitsu.com> X-ClientProxiedBy: SJ0PR13CA0055.namprd13.prod.outlook.com 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X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: dZ/ZQMbUH4kJNscRmw7A03thcyCW8XjmobCZl/ih6/BnUAgC4l64Z6TltaVC3f42LDVAfLarKAtqLYJUzh2O3UebnXCRNU2AFE0pGZ10ylQ= X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH8PR11MB6753 X-OriginatorOrg: intel.com X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: C684020014 X-Stat-Signature: 5z9r1mn15hsdu8qz3upxwwp6cnogzenk X-HE-Tag: 1679066375-325278 X-HE-Meta: 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VXmk2XMFGSEg3clHvVIKcnkE8h7H6fq+isCvV4jr7FWDHeiOS4GmWtWPaQewd8a59a63VnF7ZuxcefyEnFzM5fznviwN2qIOODeBCRw7y/N3+YYQ1cHTntaTgpA4d6dxy0DHBz3H6LrNJe//sQuQ+Qhd9n7SbQ2rUp7GWkKEqStAI1ZJFv0h0Dbg/U74Ti2KsfDDRULFFnTaQK8xbkO5mSvcvTMTk3ZHICd4rYN8PN1fJ4uhIwP6FE15AqxULpjaKuhB4SMIuMABFGOtnSkp0TN3a4Mw6JzFys2V10Cn/m3ZnCGj8vcWxKWO2ZFNCDXw1PTLyp/V7rzmGNSC8zcRQk282YuvvyahJLzao X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: lizhijian@fujitsu.com wrote: > > > On 17/03/2023 14:12, Dan Williams wrote: > > lizhijian@fujitsu.com wrote: > > [..] > >> Case D: unsupported && need your input To support this situation, the > >> makedumpfile needs to know the location of metadata for each pmem > >> namespace and the address and size of metadata in the pmem [start, > >> end) > > > > My first reaction is that you should copy what the ndctl utility does > > when it needs to manipulate or interrogate the metadata space. > > > > For example, see namespace_rw_infoblock():> > > https://github.com/pmem/ndctl/blob/main/ndctl/namespace.c#L2022 > > > > That facility uses the force_raw attribute > > ("/sys/bus/nd/devices/namespaceX.Y/force_raw") to arrange for the > > namespace to initalize without considering any pre-existing metdata > > *and* without overwriting it. In that mode makedumpfile can walk the > > namespaces and retrieve the metadata written by the previous kernel. > > For the dumping application(makedumpfile or cp), it will/should reads > /proc/vmcore to construct the dumpfile, So makedumpfile need to know > the *address* and *size/end* of metadata in the view of 1st kernel > address space. Another option, instead of passing the metadata layout into the crash kernel, is to just parse the infoblock and calculate teh boundaries of userdata and metadata. > I haven't known much about namespace_rw_infoblock() , so it is also an > option if we can know such information from it. > > My current WIP propose is to export a list linking all pmem namespaces > to vmcore, with this, the kdump kernel don't need to rely on the pmem > driver. Seems like more work to avoid using the pmem driver as new information passing infrastructure needs to be built vs reusing what is already there.