Hi Jinyang, On 11/2/20 3:04 AM, Jinyang He wrote: > Hi, > > On 11/02/2020 08:01 AM, Mauro Condarelli wrote: >> Can someone confirm (or disconfirm, of course) kexec is supposed to work on MIPS32R2? >> My attempts to use it on a MT7628-based board result in a silent hang (watchdog cuts in) >> right after: >> >> [ 201.309836] kexec_core: Starting new kernel >> [ 201.318239] Will call new kernel at 004f0000 >> [ 201.322581] Bye ... >> >> Apparently old kernel jumps to `do_kexec()` and just dies; new kernel does not give a peep. >> This can be completely my fault, of course, but I would like a confirm this is supposed to work. >> >> Thanks in advance >> Mauro Condarelli > I'm not familiar with MIPSR2. I guess your platform (MT7628-based board) > cannot use the common function. It may not give a machine specific function, too. My SoC is single core, so I don't have CONFIG_SMP. Apparently (if I read code correctly) `do_kexec()` is actually `relocate_new_kernel` (arch/mips/kernel/relocate_kernel.S). No specific provisions seem to be available for my CPU (I see just a `#ifdef CONFIG_CPU_CAVIUM_OCTEON`, which is not my case). Unfortunately my understanding of MIPS assembly is insufficient to accurately follow this code. > How CPU0 do in do_kexec()? Maybe arch/mips/kernel/reloacate_kernel.S gives us > some useful information. In this file CPU0 goes relocate_new_kernel() and other > CPUs go kexec_smp_wait() if CONFIG_SMP is enabled. Normally CPU0 will enter the > kernel_entry() of the new kernel. In my own understanding of the kexec process, > I find it extremely difficult to pass parameters. Please make sure your platform > passes the parameters necessary for startup. (See arch/mips/kernel/head.S, such as > dtb, fw_args* or other necessary parameters, this is what I said "machine specific") One possible cause of mishap is my kernel (currently) does *not* have a .dtb appended and I see no explicit option to reuse current DT. In my mips `kexec` there's a `--dtb=<file>` option but passing the same .dtb I use with u-Boot does not seem to work: # kexec -l /boot/vmlinuz --command-line="earlyprintk rootwait console=ttyS2,115200 mtdparts=spi0.0:312k(u-boot),4k(env),4k(factor y),2368k(kernel),-(filesystem) root=/dev/mmcblk0p7 tryboot=B" --dtb=/boot/u-boot.dtb # kexec -e [ 2030.833119] mtk_soc_eth 10100000.ethernet eth0: Link is Down [ 2030.848999] wlan0: deauthenticating from a0:04:60:9f:2f:f8 by local choice (Reason: 3=DEAUTH_LEAVING) Received Deauthentication event, reason: 3, from_ap: false Received error during CMD_TRIGGER_SCAN: Network is down (127) [ 2030.894637] kexec_core: Starting new kernel [ 2030.900005] Will call new kernel at 004f0000 [ 2030.904326] Bye ... <HANG!> <watchdog reset> Any hint welcome as I'm completely out of my depth here. TiA! Mauro
