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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> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: 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 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 =================================================