linux/kernel/crash_core.c, branch v6.7

crash_core: fix the check for whether crashkernel is from high memory

2023-12-13T01:20:18Z

If crash_base is equal to CRASH_ADDR_LOW_MAX, it also indicates that the crashkernel memory is allocated from high memory. However, the current check only considers the case where crash_base is greater than CRASH_ADDR_LOW_MAX. Fix it. The runtime effects is that crashkernel high memory is successfully reserved, whereas the crashkernel low memory is bypassed in this case, then kdump kernel bootup will fail because of no low memory under 4G. This patch also includes some minor cleanups. Link: https://lkml.kernel.org/r/20231209141438.77233-1-ytcoode@gmail.com Fixes: 0ab97169aa05 ("crash_core: add generic function to do reservation") Signed-off-by: Yuntao Wang Cc: Baoquan He Cc: Dave Young Cc: Vivek Goyal Cc: Zhen Lei Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton

crash_core.c: remove unneeded functions

2023-10-04T17:41:58Z

So far, nobody calls functions parse_crashkernel_high() and parse_crashkernel_low(), remove both of them. Link: https://lkml.kernel.org/r/20230914033142.676708-10-bhe@redhat.com Signed-off-by: Baoquan He Reviewed-by: Zhen Lei Cc: Catalin Marinas Cc: Chen Jiahao Signed-off-by: Andrew Morton

crash_core: move crashk_*res definition into crash_core.c

2023-10-04T17:41:58Z

Both crashk_res and crashk_low_res are used to mark the reserved crashkernel regions in iomem_resource tree. And later the generic crashkernel resrvation will be added into crash_core.c. So move crashk_res and crashk_low_res definition into crash_core.c to avoid compiling error if CONFIG_CRASH_CORE=on while CONFIG_KEXEC_CORE is unset. Meanwhile include in if generic reservation is needed. In that case, need be added by ARCH. In asm/crash_core.h, ARCH can provide its own macro definitions to override macros in if needed. Wrap the including into CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION ifdeffery scope to avoid compiling error in other ARCH-es which don't take the generic reservation way yet. Link: https://lkml.kernel.org/r/20230914033142.676708-6-bhe@redhat.com Signed-off-by: Baoquan He Reviewed-by: Zhen Lei Cc: Catalin Marinas Cc: Chen Jiahao Signed-off-by: Andrew Morton

crash_core: add generic function to do reservation

2023-10-04T17:41:58Z

In architecture like x86_64, arm64 and riscv, they have vast virtual address space and usually have huge physical memory RAM. Their crashkernel reservation doesn't have to be limited under 4G RAM, but can be extended to the whole physical memory via crashkernel=,high support. Now add function reserve_crashkernel_generic() to reserve crashkernel memory if users specify any case of kernel pamameters, like crashkernel=xM[@offset] or crashkernel=,high|low. This is preparation to simplify code of crashkernel=,high support in architecutures. Link: https://lkml.kernel.org/r/20230914033142.676708-5-bhe@redhat.com Signed-off-by: Baoquan He Reviewed-by: Zhen Lei Cc: Catalin Marinas Cc: Chen Jiahao Signed-off-by: Andrew Morton

crash_core: change parse_crashkernel() to support crashkernel=,high|low parsing

2023-10-04T17:41:58Z

Now parse_crashkernel() is a real entry point for all kinds of crahskernel parsing on any architecture. And wrap the crahskernel=,high|low handling inside CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION ifdeffery scope. Link: https://lkml.kernel.org/r/20230914033142.676708-4-bhe@redhat.com Signed-off-by: Baoquan He Reviewed-by: Zhen Lei Cc: Catalin Marinas Cc: Chen Jiahao Signed-off-by: Andrew Morton

crash_core: change the prototype of function parse_crashkernel()

2023-10-04T17:41:58Z

Add two parameters 'low_size' and 'high' to function parse_crashkernel(), later crashkernel=,high|low parsing will be added. Make adjustments in all call sites of parse_crashkernel() in arch. Link: https://lkml.kernel.org/r/20230914033142.676708-3-bhe@redhat.com Signed-off-by: Baoquan He Reviewed-by: Zhen Lei Cc: Catalin Marinas Cc: Chen Jiahao Signed-off-by: Andrew Morton

crash_core.c: remove unnecessary parameter of function

2023-10-04T17:41:58Z

Patch series "kdump: use generic functions to simplify crashkernel reservation in arch", v3. In the current arm64, crashkernel=,high support has been finished after several rounds of posting and careful reviewing. The code in arm64 which parses crashkernel kernel parameters firstly, then reserve memory can be a good example for other ARCH to refer to. Whereas in x86_64, the code mixing crashkernel parameter parsing and memory reserving is twisted, and looks messy. Refactoring the code to make it more readable maintainable is necessary. Here, firstly abstract the crashkernel parameter parsing code into parse_crashkernel() to make it be able to parse crashkernel=,high|low. Then abstract the crashkernel memory reserving code into a generic function reserve_crashkernel_generic(). Finally, in ARCH which crashkernel=,high support is needed, a simple arch_reserve_crashkernel() can be added to call above two functions. This can remove the duplicated implmentation code in each ARCH, like arm64, x86_64 and riscv. crashkernel=512M,high crashkernel=512M,high crashkernel=256M,low crashkernel=512M,high crashkernel=0M,low crashkernel=0M,high crashkernel=256M,low crashkernel=512M crashkernel=512M@0x4f000000 crashkernel=1G-4G:256M,4G-64G:320M,64G-:576M crashkernel=0M This patch (of 9): In all call sites of __parse_crashkernel(), the parameter 'name' is hardcoded as "crashkernel=". So remove the unnecessary parameter 'name', add local varibale 'name' inside __parse_crashkernel() instead. Link: https://lkml.kernel.org/r/20230914033142.676708-1-bhe@redhat.com Link: https://lkml.kernel.org/r/20230914033142.676708-2-bhe@redhat.com Signed-off-by: Baoquan He Reviewed-by: Zhen Lei Cc: Catalin Marinas Cc: Chen Jiahao Cc: Zhen Lei Signed-off-by: Andrew Morton

Crash: add lock to serialize crash hotplug handling

2023-09-30T00:20:48Z

Eric reported that handling corresponding crash hotplug event can be failed easily when many memory hotplug event are notified in a short period. They failed because failing to take __kexec_lock. ======= [ 78.714569] Fallback order for Node 0: 0 [ 78.714575] Built 1 zonelists, mobility grouping on. Total pages: 1817886 [ 78.717133] Policy zone: Normal [ 78.724423] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate [ 78.727207] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate [ 80.056643] PEFILE: Unsigned PE binary ======= The memory hotplug events are notified very quickly and very many, while the handling of crash hotplug is much slower relatively. So the atomic variable __kexec_lock and kexec_trylock() can't guarantee the serialization of crash hotplug handling. Here, add a new mutex lock __crash_hotplug_lock to serialize crash hotplug handling specifically. This doesn't impact the usage of __kexec_lock. Link: https://lkml.kernel.org/r/20230926120905.392903-1-bhe@redhat.com Fixes: 247262756121 ("crash: add generic infrastructure for crash hotplug support") Signed-off-by: Baoquan He Tested-by: Eric DeVolder Reviewed-by: Eric DeVolder Reviewed-by: Valentin Schneider Cc: Sourabh Jain Cc: Signed-off-by: Andrew Morton

Merge tag 'mm-nonmm-stable-2023-08-28-22-48' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2023-08-29T21:53:51Z

Pull non-MM updates from Andrew Morton: - An extensive rework of kexec and crash Kconfig from Eric DeVolder ("refactor Kconfig to consolidate KEXEC and CRASH options") - kernel.h slimming work from Andy Shevchenko ("kernel.h: Split out a couple of macros to args.h") - gdb feature work from Kuan-Ying Lee ("Add GDB memory helper commands") - vsprintf inclusion rationalization from Andy Shevchenko ("lib/vsprintf: Rework header inclusions") - Switch the handling of kdump from a udev scheme to in-kernel handling, by Eric DeVolder ("crash: Kernel handling of CPU and memory hot un/plug") - Many singleton patches to various parts of the tree * tag 'mm-nonmm-stable-2023-08-28-22-48' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (81 commits) document while_each_thread(), change first_tid() to use for_each_thread() drivers/char/mem.c: shrink character device's devlist[] array x86/crash: optimize CPU changes crash: change crash_prepare_elf64_headers() to for_each_possible_cpu() crash: hotplug support for kexec_load() x86/crash: add x86 crash hotplug support crash: memory and CPU hotplug sysfs attributes kexec: exclude elfcorehdr from the segment digest crash: add generic infrastructure for crash hotplug support crash: move a few code bits to setup support of crash hotplug kstrtox: consistently use _tolower() kill do_each_thread() nilfs2: fix WARNING in mark_buffer_dirty due to discarded buffer reuse scripts/bloat-o-meter: count weak symbol sizes treewide: drop CONFIG_EMBEDDED lockdep: fix static memory detection even more lib/vsprintf: declare no_hash_pointers in sprintf.h lib/vsprintf: split out sprintf() and friends kernel/fork: stop playing lockless games for exe_file replacement adfs: delete unused "union adfs_dirtail" definition ...

crash: change crash_prepare_elf64_headers() to for_each_possible_cpu()

2023-08-24T23:25:14Z

The function crash_prepare_elf64_headers() generates the elfcorehdr which describes the CPUs and memory in the system for the crash kernel. In particular, it writes out ELF PT_NOTEs for memory regions and the CPUs in the system. With respect to the CPUs, the current implementation utilizes for_each_present_cpu() which means that as CPUs are added and removed, the elfcorehdr must again be updated to reflect the new set of CPUs. The reasoning behind the move to use for_each_possible_cpu(), is: - At kernel boot time, all percpu crash_notes are allocated for all possible CPUs; that is, crash_notes are not allocated dynamically when CPUs are plugged/unplugged. Thus the crash_notes for each possible CPU are always available. - The crash_prepare_elf64_headers() creates an ELF PT_NOTE per CPU. Changing to for_each_possible_cpu() is valid as the crash_notes pointed to by each CPU PT_NOTE are present and always valid. Furthermore, examining a common crash processing path of: kernel panic -> crash kernel -> makedumpfile -> 'crash' analyzer elfcorehdr /proc/vmcore vmcore reveals how the ELF CPU PT_NOTEs are utilized: - Upon panic, each CPU is sent an IPI and shuts itself down, recording its state in its crash_notes. When all CPUs are shutdown, the crash kernel is launched with a pointer to the elfcorehdr. - The crash kernel via linux/fs/proc/vmcore.c does not examine or use the contents of the PT_NOTEs, it exposes them via /proc/vmcore. - The makedumpfile utility uses /proc/vmcore and reads the CPU PT_NOTEs to craft a nr_cpus variable, which is reported in a header but otherwise generally unused. Makedumpfile creates the vmcore. - The 'crash' dump analyzer does not appear to reference the CPU PT_NOTEs. Instead it looks-up the cpu_[possible|present|onlin]_mask symbols and directly examines those structure contents from vmcore memory. From that information it is able to determine which CPUs are present and online, and locate the corresponding crash_notes. Said differently, it appears that 'crash' analyzer does not rely on the ELF PT_NOTEs for CPUs; rather it obtains the information directly via kernel symbols and the memory within the vmcore. (There maybe other vmcore generating and analysis tools that do use these PT_NOTEs, but 'makedumpfile' and 'crash' seems to be the most common solution.) This results in the benefit of having all CPUs described in the elfcorehdr, and therefore reducing the need to re-generate the elfcorehdr on CPU changes, at the small expense of an additional 56 bytes per PT_NOTE for not-present-but-possible CPUs. On systems where kexec_file_load() syscall is utilized, all the above is valid. On systems where kexec_load() syscall is utilized, there may be the need for the elfcorehdr to be regenerated once. The reason being that some archs only populate the 'present' CPUs from the /sys/devices/system/cpus entries, which the userspace 'kexec' utility uses to generate the userspace-supplied elfcorehdr. In this situation, one memory or CPU change will rewrite the elfcorehdr via the crash_prepare_elf64_headers() function and now all possible CPUs will be described, just as with kexec_file_load() syscall. Link: https://lkml.kernel.org/r/20230814214446.6659-8-eric.devolder@oracle.com Signed-off-by: Eric DeVolder Suggested-by: Sourabh Jain Reviewed-by: Sourabh Jain Acked-by: Hari Bathini Acked-by: Baoquan He Cc: Akhil Raj Cc: Bjorn Helgaas Cc: Borislav Petkov (AMD) Cc: Boris Ostrovsky Cc: Dave Hansen Cc: Dave Young Cc: David Hildenbrand Cc: Eric W. Biederman Cc: Greg Kroah-Hartman Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Jonathan Corbet Cc: Konrad Rzeszutek Wilk Cc: Mimi Zohar Cc: Naveen N. Rao Cc: Oscar Salvador Cc: "Rafael J. Wysocki" Cc: Sean Christopherson Cc: Takashi Iwai Cc: Thomas Gleixner Cc: Thomas Weißschuh Cc: Valentin Schneider Cc: Vivek Goyal Cc: Vlastimil Babka Signed-off-by: Andrew Morton