Hi Manish, On 04/10/16 11:05, Manish Jaggi wrote: > On 10/04/2016 03:16 PM, James Morse wrote: >> On 03/10/16 13:41, Manish Jaggi wrote: >>> On 10/03/2016 04:34 PM, AKASHI Takahiro wrote: >>>> On Mon, Oct 03, 2016 at 01:24:34PM +0530, Manish Jaggi wrote: >>>>> First kernel is booted with mem=2G crashkernel=1G command line option. >>>>> While the system has 64G memory. >> >>>> Are you saying that "mem=..." doesn't have any effect? >>> What I am saying it that If the first kernel is booted using mem= option and crashkernel= option >>> the memory for second kernel has to be withing the crashkernel size. >>> As per /proc/iomem System RAM the information is correct, but the /proc/meminfo is showing total memory >>> much more than the first kernel had in first place. >> >> So your second crashkernel has 63G of memory? Unless you provide the same 'mem=' >> to the kdump kernel, this is the expected behaviour. The >> DT:/reserved-memory/crash_dump describes the memory not to use. >> >> On your first boot with 'mem=2G' memblock_mem_limit_remove_map() called from >> arm64_memblock_init() removed the top 62G of memory. Neither the first kernel >> nor kexec-tools know about the top 62G. >> When you run kexec-tools, it describes what it sees in /proc/iomem in the >> DT:/reserved-memory/crash_dump, which is just the remaining 1G of memory. >> >> When we crash and reboot, the crash kernel discovers all 64G of memory from the >> EFI memory map. > So the iomem and meminfo should be same or different for the second kernel? > Also i assumed that crashkernel=1G should restrict the second kernels to 1G. Not with v26 of this series. What should it do with the 62G of memory that was removed by booting with 'mem=2G'? It isn't part of the crashkernel reserved area, and it isn't part of the vmcore described in elfcorehdr either... > This is my understanding from the description. It should not require a second mem= option >> kexec-tools described the 1G of memory that the first kernel was using in the >> DT:/reserved-memory/crash_dump node, so early_init_fdt_scan_reserved_mem() >> reserves the 1G of memory the first kernel used. This leaves us with 63G of memory. >> >> This may change with the next version of kdump if it switches back to using >> DT:/chosen/linux,usable-memory-range. >> If you need v26 to avoid the top 62G of memory, you need to provide the same >> 'mem=' to the first and second kernel. > If I provide for second kernel, I dont see any prints after Bye. > Have you tired this anytime? Yes, on juno-r1 passing 'mem=2G' to both the first and second kernel causes only the first 2G of memory to be used with this pattern: first kernel: [1G used for linux] [1G reserved for Crash kernel] [6G memory hidden] kdump kernel: [1G vmcore] [1G used for linux] [6G memory hidden] >>>>> 1.2 Live crash dump fails with error >> >> ... do we expect this to work? I don't think it has anything to do with this >> series... >> > Why it should not? > I saved the vmcore file while in second kernel. Since crash without vmcore file didnt run, > Tried with vmcore file and it worked. Its just that if you want to boot a second kernel > with read only file system without network live crash dump analysis is handy. Ah, you want to run /usr/bin/crash with the kdump boot of linux. You still need to tell it where to find the memory image: "crash /path/to/vmlinux /proc/vmcore" should do the trick. Thanks, James
