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[2003:cb:c70b:e100:38d6:8aa1:11b0:a20a]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-434d52c0bc7sm23514855e9.35.2024.12.04.04.54.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Dec 2024 04:54:46 -0800 (PST) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: 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, David Hildenbrand , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?utf-8?q?Eugenio_P=C3=A9rez?= , Baoquan He , Vivek Goyal , Dave Young , Thomas Huth , Cornelia Huck , Janosch Frank , Claudio Imbrenda , Eric Farman , Andrew Morton Subject: [PATCH v2 00/12] fs/proc/vmcore: kdump support for virtio-mem on s390 Date: Wed, 4 Dec 2024 13:54:31 +0100 Message-ID: <20241204125444.1734652-1-david@redhat.com> X-Mailer: git-send-email 2.47.1 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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 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