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Tsirkin" , Jason Wang , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , Vivek Goyal , Dave Young , Thomas Huth , Cornelia Huck , Janosch Frank , Claudio Imbrenda , Eric Farman , Andrew Morton Subject: Re: [PATCH v1 07/11] fs/proc/vmcore: introduce PROC_VMCORE_DEVICE_RAM to detect device RAM ranges in 2nd kernel Message-ID: References: <20241025151134.1275575-1-david@redhat.com> <20241025151134.1275575-8-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241025151134.1275575-8-david@redhat.com> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 X-Stat-Signature: sd73upsqxn7azjsxwpggjy4fmgcw5o45 X-Rspam-User: X-Rspamd-Queue-Id: 80495180023 X-Rspamd-Server: rspam02 X-HE-Tag: 1732097648-451134 X-HE-Meta: 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 fPWdZFF6 kqMTkLOyJh0bB+VgwDgr0WnJg1zuNsUYR61UQoK47W4KDgcK2FaCjZUYNaT2vLRCu8mF918uysxq9ir0eXApKu4aYrpE74ox9kgnwvQHJ7F1HRYDUr/q+EUV2x3g0afspTaz7B9c/h0zf/9GedI9MAaSUmgSc1bYt13vszq0nmXMIaYhWV73yLXEHrNDY9aLbmw1gDJdnhRiwMRLH36txAd5z1rHWwZT1DfwaBeItJaJatitrqxsS7iRSwe82H5kuAFzuLCZPVbHljAz8JBmrFauZUEzBf6gbSU+BhfA9z7qVCybfLYEjrNMqDmwsQD9MjjX25EVQXLcWbw15VQQVs1w6EroWMaRn7bhwZMSoCjieS+5HdfSc17BkLTMoX/GmnyEa8S6eO/e5x0YPHECZ0Dh4RSqzhcfD0PCWKlZB1TmZc1I= 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: List-Subscribe: List-Unsubscribe: On 10/25/24 at 05:11pm, David Hildenbrand wrote: > s390 allocates+prepares the elfcore hdr in the dump (2nd) kernel, not in > the crashed kernel. > > RAM provided by memory devices such as virtio-mem can only be detected > using the device driver; when vmcore_init() is called, these device > drivers are usually not loaded yet, or the devices did not get probed > yet. Consequently, on s390 these RAM ranges will not be included in > the crash dump, which makes the dump partially corrupt and is > unfortunate. > > Instead of deferring the vmcore_init() call, to an (unclear?) later point, > let's reuse the vmcore_cb infrastructure to obtain device RAM ranges as > the device drivers probe the device and get access to this information. > > Then, we'll add these ranges to the vmcore, adding more PT_LOAD > entries and updating the offsets+vmcore size. > > Use Kconfig tricks to include this code automatically only if (a) there is > a device driver compiled that implements the callback > (PROVIDE_PROC_VMCORE_DEVICE_RAM) and; (b) the architecture actually needs > this information (NEED_PROC_VMCORE_DEVICE_RAM). > > The current target use case is s390, which only creates an elf64 > elfcore, so focusing on elf64 is sufficient. > > Signed-off-by: David Hildenbrand > --- > fs/proc/Kconfig | 25 ++++++ > fs/proc/vmcore.c | 156 +++++++++++++++++++++++++++++++++++++ > include/linux/crash_dump.h | 9 +++ > 3 files changed, 190 insertions(+) > > diff --git a/fs/proc/Kconfig b/fs/proc/Kconfig > index d80a1431ef7b..1e11de5f9380 100644 > --- a/fs/proc/Kconfig > +++ b/fs/proc/Kconfig > @@ -61,6 +61,31 @@ config PROC_VMCORE_DEVICE_DUMP > as ELF notes to /proc/vmcore. You can still disable device > dump using the kernel command line option 'novmcoredd'. > > +config PROVIDE_PROC_VMCORE_DEVICE_RAM > + def_bool n > + > +config NEED_PROC_VMCORE_DEVICE_RAM > + def_bool n > + > +config PROC_VMCORE_DEVICE_RAM > + def_bool y > + depends on PROC_VMCORE > + depends on NEED_PROC_VMCORE_DEVICE_RAM > + depends on PROVIDE_PROC_VMCORE_DEVICE_RAM Kconfig item is always a thing I need learn to master. When I checked this part, I have to write them down to deliberate. I am wondering if below 'simple version' works too and more understandable. Please help point out what I have missed. ===========simple version====== config PROC_VMCORE_DEVICE_RAM def_bool y depends on PROC_VMCORE && VIRTIO_MEM depends on NEED_PROC_VMCORE_DEVICE_RAM config S390 select NEED_PROC_VMCORE_DEVICE_RAM ============ ======= config items extracted from this patchset==== config PROVIDE_PROC_VMCORE_DEVICE_RAM def_bool n config NEED_PROC_VMCORE_DEVICE_RAM def_bool n config PROC_VMCORE_DEVICE_RAM def_bool y depends on PROC_VMCORE depends on NEED_PROC_VMCORE_DEVICE_RAM depends on PROVIDE_PROC_VMCORE_DEVICE_RAM config VIRTIO_MEM depends on X86_64 || ARM64 || RISCV ~~~~~ I don't get why VIRTIO_MEM dones't depend on S390 if s390 need PROC_VMCORE_DEVICE_RAM. ...... select PROVIDE_PROC_VMCORE_DEVICE_RAM if PROC_VMCORE config S390 select NEED_PROC_VMCORE_DEVICE_RAM if PROC_VMCORE =================================================