diff options
Diffstat (limited to 'Documentation/powerpc')
| -rw-r--r-- | Documentation/powerpc/firmware-assisted-dump.rst | 55 |
1 files changed, 30 insertions, 25 deletions
diff --git a/Documentation/powerpc/firmware-assisted-dump.rst b/Documentation/powerpc/firmware-assisted-dump.rst index 563c021df539..d912755067d2 100644 --- a/Documentation/powerpc/firmware-assisted-dump.rst +++ b/Documentation/powerpc/firmware-assisted-dump.rst @@ -9,18 +9,18 @@ a crashed system, and to do so from a fully-reset system, and to minimize the total elapsed time until the system is back in production use. -- Firmware assisted dump (fadump) infrastructure is intended to replace +- Firmware-Assisted Dump (FADump) infrastructure is intended to replace the existing phyp assisted dump. - Fadump uses the same firmware interfaces and memory reservation model as phyp assisted dump. -- Unlike phyp dump, fadump exports the memory dump through /proc/vmcore +- Unlike phyp dump, FADump exports the memory dump through /proc/vmcore in the ELF format in the same way as kdump. This helps us reuse the kdump infrastructure for dump capture and filtering. - Unlike phyp dump, userspace tool does not need to refer any sysfs interface while reading /proc/vmcore. -- Unlike phyp dump, fadump allows user to release all the memory reserved +- Unlike phyp dump, FADump allows user to release all the memory reserved for dump, with a single operation of echo 1 > /sys/kernel/fadump_release_mem. -- Once enabled through kernel boot parameter, fadump can be +- Once enabled through kernel boot parameter, FADump can be started/stopped through /sys/kernel/fadump_registered interface (see sysfs files section below) and can be easily integrated with kdump service start/stop init scripts. @@ -34,7 +34,7 @@ dump offers several strong, practical advantages: in a clean, consistent state. - Once the dump is copied out, the memory that held the dump is immediately available to the running kernel. And therefore, - unlike kdump, fadump doesn't need a 2nd reboot to get back + unlike kdump, FADump doesn't need a 2nd reboot to get back the system to the production configuration. The above can only be accomplished by coordination with, @@ -63,7 +63,7 @@ as follows: boot successfully. For syntax of crashkernel= parameter, refer to Documentation/admin-guide/kdump/kdump.rst. If any offset is provided in crashkernel= parameter, it will be ignored - as fadump uses a predefined offset to reserve memory + as FADump uses a predefined offset to reserve memory for boot memory dump preservation in case of a crash. - After the low memory (boot memory) area has been saved, the @@ -123,7 +123,7 @@ blocking this significant chunk of memory from production kernel. Hence, the implementation uses the Linux kernel's Contiguous Memory Allocator (CMA) for memory reservation if CMA is configured for kernel. With CMA reservation this memory will be available for applications to -use it, while kernel is prevented from using it. With this fadump will +use it, while kernel is prevented from using it. With this FADump will still be able to capture all of the kernel memory and most of the user space memory except the user pages that were present in CMA region:: @@ -173,14 +173,14 @@ KDump, as dump mechanism. The tools to examine the dump will be same as the ones used for kdump. -How to enable firmware-assisted dump (fadump): +How to enable firmware-assisted dump (FADump): ---------------------------------------------- 1. Set config option CONFIG_FA_DUMP=y and build kernel. 2. Boot into linux kernel with 'fadump=on' kernel cmdline option. - By default, fadump reserved memory will be initialized as CMA area. + By default, FADump reserved memory will be initialized as CMA area. Alternatively, user can boot linux kernel with 'fadump=nocma' to - prevent fadump to use CMA. + prevent FADump to use CMA. 3. Optionally, user can also set 'crashkernel=' kernel cmdline to specify size of the memory to reserve for boot memory dump preservation. @@ -206,29 +206,29 @@ the control files and debugfs file to display memory reserved region. Here is the list of files under kernel sysfs: /sys/kernel/fadump_enabled - This is used to display the fadump status. + This is used to display the FADump status. - - 0 = fadump is disabled - - 1 = fadump is enabled + - 0 = FADump is disabled + - 1 = FADump is enabled This interface can be used by kdump init scripts to identify if - fadump is enabled in the kernel and act accordingly. + FADump is enabled in the kernel and act accordingly. /sys/kernel/fadump_registered - This is used to display the fadump registration status as well - as to control (start/stop) the fadump registration. + This is used to display the FADump registration status as well + as to control (start/stop) the FADump registration. - - 0 = fadump is not registered. - - 1 = fadump is registered and ready to handle system crash. + - 0 = FADump is not registered. + - 1 = FADump is registered and ready to handle system crash. - To register fadump echo 1 > /sys/kernel/fadump_registered and + To register FADump echo 1 > /sys/kernel/fadump_registered and echo 0 > /sys/kernel/fadump_registered for un-register and stop the - fadump. Once the fadump is un-registered, the system crash will not + FADump. Once the FADump is un-registered, the system crash will not be handled and vmcore will not be captured. This interface can be easily integrated with kdump service start/stop. /sys/kernel/fadump_release_mem - This file is available only when fadump is active during + This file is available only when FADump is active during second kernel. This is used to release the reserved memory region that are held for saving crash dump. To release the reserved memory echo 1 to it:: @@ -246,21 +246,25 @@ Here is the list of files under powerpc debugfs: (Assuming debugfs is mounted on /sys/kernel/debug directory.) /sys/kernel/debug/powerpc/fadump_region - This file shows the reserved memory regions if fadump is + This file shows the reserved memory regions if FADump is enabled otherwise this file is empty. The output format is:: <region>: [<start>-<end>] <reserved-size> bytes, Dumped: <dump-size> + and for kernel DUMP region is: + + DUMP: Src: <src-addr>, Dest: <dest-addr>, Size: <size>, Dumped: # bytes + e.g. - Contents when fadump is registered during first kernel:: + Contents when FADump is registered during first kernel:: # cat /sys/kernel/debug/powerpc/fadump_region CPU : [0x0000006ffb0000-0x0000006fff001f] 0x40020 bytes, Dumped: 0x0 HPTE: [0x0000006fff0020-0x0000006fff101f] 0x1000 bytes, Dumped: 0x0 DUMP: [0x0000006fff1020-0x0000007fff101f] 0x10000000 bytes, Dumped: 0x0 - Contents when fadump is active during second kernel:: + Contents when FADump is active during second kernel:: # cat /sys/kernel/debug/powerpc/fadump_region CPU : [0x0000006ffb0000-0x0000006fff001f] 0x40020 bytes, Dumped: 0x40020 @@ -268,6 +272,7 @@ Here is the list of files under powerpc debugfs: DUMP: [0x0000006fff1020-0x0000007fff101f] 0x10000000 bytes, Dumped: 0x10000000 : [0x00000010000000-0x0000006ffaffff] 0x5ffb0000 bytes, Dumped: 0x5ffb0000 + NOTE: Please refer to Documentation/filesystems/debugfs.txt on how to mount the debugfs filesystem. @@ -278,7 +283,7 @@ TODO: - Need to come up with the better approach to find out more accurate boot memory size that is required for a kernel to boot successfully when booted with restricted memory. - - The fadump implementation introduces a fadump crash info structure + - The FADump implementation introduces a FADump crash info structure in the scratch area before the ELF core header. The idea of introducing this structure is to pass some important crash info data to the second kernel which will help second kernel to populate ELF core header with |