On 08/21/25 at 12:32pm, Usama Arif wrote: > > > On 21/08/2025 04:28, Baoquan He wrote: > > Hi, > > > > On 08/11/25 at 04:37pm, Usama Arif wrote: > >> If the kernel is enabled with CONFIG_BOOT_CONFIG_FORCE, it will > >> always append the bootconfig at the start of the kernel commandline. > >> If reuse-cmdline option is used in kexec, the bootconfig will be > >> repeatedly appended at the start of the commandline on every kexec. > >> As there is a limit on the size of kernel commandline that can be > >> used, --reuse-cmdline option will break kexec depending on the > >> size of bootconfig on repeated kexec. > >> > >> Bootconfig is embedded in the kernel, so it should not be considered > >> when reusing kernel command line. > >> Modify get_command_line() to first attempt reading kernel parameters > >> from /proc/bootconfig before falling back to /proc/cmdline. This allows > >> kexec to use the original boot parameters without bootconfig which > >> is embedded in the kernel. > > > > Thanks for the great fix. While I have some questions about the change. > > > > 1, if we can read kernel parameters from /proc/bootconfig, does it mean > > we will skip other kernel parameters, e.g I set some parameters in > > grub, meanwhile set bootconfg? Is this allowed? > > Hi Baoquan, > > Thanks for the questions. > > /proc/bootconfig treats the parameters from bootconfig separate from the rest. > i.e. parameters from grub will be coming after "# Parameters from bootloader:" > in /proc/bootconfig. It shouldn't skip grub parameters. For e.g. on my machine > > cat /proc/bootconfig > kernel.csdlock_debug = "1" > kernel.mitigations = "off" > # Parameters from bootloader: > # crashkernel=..... > > > kernel.csdlock_debug = "1" > kernel.mitigations = "off" > comes from bootconfig, while the crashkernel and the rest come from > bootloader [1] > > [1] > https://elixir.bootlin.com/linux/v6.16.1/source/Documentation/filesystems/proc.rst#L739 > > > > > 2. If /proc/bootconfig includes the whole kernel parameters of the > > runnign kernel, setup_boot_config() will parse and append bootconfig > > to kernel cmdline again, right? But it doesn't matter. > > /proc/bootconfig contains the whole parameters, but the bootconfig is > seperated by "# Parameters from bootloader:". > If we repeatedly kexec using /proc/cmdline, we will continuously append > bootconfig, > and wont be able to kexec anymore once the commandline gets too big..
I see, then it should be OK. I thought /proc/bootconfig only contains the content of bootconfig, and was worried about the incomplete kernel cmdline passing to 2nd kernel. Thanks for the explanation. For the patch, Acked-by: Baoquan He <b...@redhat.com>
