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Tsirkin" To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, virtualization@lists.linux.dev, kvm@vger.kernel.org, linux-fsdevel@vger.kernel.org, kexec@lists.infradead.org, Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Jason Wang , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , Baoquan He , Vivek Goyal , Dave Young , Thomas Huth , Cornelia Huck , Janosch Frank , Claudio Imbrenda , Eric Farman , Andrew Morton Subject: Re: [PATCH v2 00/12] fs/proc/vmcore: kdump support for virtio-mem on s390 Message-ID: <20250108070407-mutt-send-email-mst@kernel.org> References: <20241204125444.1734652-1-david@redhat.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20241204125444.1734652-1-david@redhat.com> On Wed, Dec 04, 2024 at 01:54:31PM +0100, David Hildenbrand wrote: > The only "different than everything else" thing about virtio-mem on s390 > is kdump: The crash (2nd) kernel allocates+prepares the elfcore hdr > during fs_init()->vmcore_init()->elfcorehdr_alloc(). Consequently, the > kdump kernel must detect memory ranges of the crashed kernel to > include via PT_LOAD in the vmcore. > > On other architectures, all RAM regions (boot + hotplugged) can easily be > observed on the old (to crash) kernel (e.g., using /proc/iomem) to create > the elfcore hdr. > > On s390, information about "ordinary" memory (heh, "storage") can be > obtained by querying the hypervisor/ultravisor via SCLP/diag260, and > that information is stored early during boot in the "physmem" memblock > data structure. > > But virtio-mem memory is always detected by as device driver, which is > usually build as a module. So in the crash kernel, this memory can only be > properly detected once the virtio-mem driver started up. > > The virtio-mem driver already supports the "kdump mode", where it won't > hotplug any memory but instead queries the device to implement the > pfn_is_ram() callback, to avoid reading unplugged memory holes when reading > the vmcore. > > With this series, if the virtio-mem driver is included in the kdump > initrd -- which dracut already takes care of under Fedora/RHEL -- it will > now detect the device RAM ranges on s390 once it probes the devices, to add > them to the vmcore using the same callback mechanism we already have for > pfn_is_ram(). > > To add these device RAM ranges to the vmcore ("patch the vmcore"), we will > add new PT_LOAD entries that describe these memory ranges, and update > all offsets vmcore size so it is all consistent. > > My testing when creating+analyzing crash dumps with hotplugged virtio-mem > memory (incl. holes) did not reveal any surprises. > > Patch #1 -- #7 are vmcore preparations and cleanups > Patch #8 adds the infrastructure for drivers to report device RAM > Patch #9 + #10 are virtio-mem preparations > Patch #11 implements virtio-mem support to report device RAM > Patch #12 activates it for s390, implementing a new function to fill > PT_LOAD entry for device RAM Who is merging this? virtio parts: Acked-by: Michael S. Tsirkin > v1 -> v2: > * "fs/proc/vmcore: convert vmcore_cb_lock into vmcore_mutex" > -> Extend patch description > * "fs/proc/vmcore: replace vmcoredd_mutex by vmcore_mutex" > -> Extend patch description > * "fs/proc/vmcore: disallow vmcore modifications while the vmcore is open" > -> Disallow modifications only if it is currently open, but warn if it > was already open and got closed again. > -> Track vmcore_open vs. vmcore_opened > -> Extend patch description > * "fs/proc/vmcore: prefix all pr_* with "vmcore:"" > -> Added > * "fs/proc/vmcore: move vmcore definitions out if kcore.h" > -> Call it "vmcore_range" > -> Place vmcoredd_node into vmcore.c > -> Adjust patch subject + description > * "fs/proc/vmcore: factor out allocating a vmcore range and adding it to a > list" > -> Adjust to "vmcore_range" > * "fs/proc/vmcore: factor out freeing a list of vmcore ranges" > -> Adjust to "vmcore_range" > * "fs/proc/vmcore: introduce PROC_VMCORE_DEVICE_RAM to detect device RAM > ranges in 2nd kernel" > -> Drop PROVIDE_PROC_VMCORE_DEVICE_RAM for now > -> Simplify Kconfig a bit > -> Drop "Kdump:" from warnings/errors > -> Perform Elf64 check first > -> Add regions also if the vmcore was opened, but got closed again. But > warn in any case, because it is unexpected. > -> Adjust patch description > * "virtio-mem: support CONFIG_PROC_VMCORE_DEVICE_RAM" > -> "depends on VIRTIO_MEM" for PROC_VMCORE_DEVICE_RAM > > > Cc: Heiko Carstens > Cc: Vasily Gorbik > Cc: Alexander Gordeev > Cc: Christian Borntraeger > Cc: Sven Schnelle > Cc: "Michael S. Tsirkin" > Cc: Jason Wang > Cc: Xuan Zhuo > Cc: "Eugenio Pérez" > Cc: Baoquan He > Cc: Vivek Goyal > Cc: Dave Young > Cc: Thomas Huth > Cc: Cornelia Huck > Cc: Janosch Frank > Cc: Claudio Imbrenda > Cc: Eric Farman > Cc: Andrew Morton > > David Hildenbrand (12): > fs/proc/vmcore: convert vmcore_cb_lock into vmcore_mutex > fs/proc/vmcore: replace vmcoredd_mutex by vmcore_mutex > fs/proc/vmcore: disallow vmcore modifications while the vmcore is open > fs/proc/vmcore: prefix all pr_* with "vmcore:" > fs/proc/vmcore: move vmcore definitions out of kcore.h > fs/proc/vmcore: factor out allocating a vmcore range and adding it to > a list > fs/proc/vmcore: factor out freeing a list of vmcore ranges > fs/proc/vmcore: introduce PROC_VMCORE_DEVICE_RAM to detect device RAM > ranges in 2nd kernel > virtio-mem: mark device ready before registering callbacks in kdump > mode > virtio-mem: remember usable region size > virtio-mem: support CONFIG_PROC_VMCORE_DEVICE_RAM > s390/kdump: virtio-mem kdump support (CONFIG_PROC_VMCORE_DEVICE_RAM) > > arch/s390/Kconfig | 1 + > arch/s390/kernel/crash_dump.c | 39 ++++- > drivers/virtio/virtio_mem.c | 103 ++++++++++++- > fs/proc/Kconfig | 19 +++ > fs/proc/vmcore.c | 283 ++++++++++++++++++++++++++-------- > include/linux/crash_dump.h | 41 +++++ > include/linux/kcore.h | 13 -- > 7 files changed, 407 insertions(+), 92 deletions(-) > > > base-commit: feffde684ac29a3b7aec82d2df850fbdbdee55e4 > -- > 2.47.1