Messages in this thread | | | Date | Wed, 13 Mar 2024 06:58:57 +0100 | Subject | Re: kexec verbose dumps with 6.8 [was: [PATCH v4 1/7] kexec_file: add kexec_file flag to control debug printing] | From | Jiri Slaby <> |
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Hi,
On 13. 03. 24, 1:48, Baoquan He wrote: > Hi Jiri, > > On 03/12/24 at 10:58am, Jiri Slaby wrote: >> On 13. 12. 23, 6:57, Baoquan He wrote: > ... snip... >>> --- a/include/linux/kexec.h >>> +++ b/include/linux/kexec.h >> ... >>> @@ -500,6 +500,13 @@ static inline int crash_hotplug_memory_support(void) { return 0; } >>> static inline unsigned int crash_get_elfcorehdr_size(void) { return 0; } >>> #endif >>> +extern bool kexec_file_dbg_print; >>> + >>> +#define kexec_dprintk(fmt, ...) \ >>> + printk("%s" fmt, \ >>> + kexec_file_dbg_print ? KERN_INFO : KERN_DEBUG, \ >>> + ##__VA_ARGS__) >> >> This means you dump it _always_. Only with different levels. > > It dumped always too with pr_debug() before, I just add a switch to > control it's pr_info() or pr_debug().
Not really, see below.
>> >> And without any prefix whatsoever, so people see bloat like this in their >> log now: >> [ +0.000001] 0000000000001000-000000000009ffff (1) >> [ +0.000002] 000000007f96d000-000000007f97efff (3) >> [ +0.000002] 0000000000800000-0000000000807fff (4) >> [ +0.000001] 000000000080b000-000000000080bfff (4) >> [ +0.000002] 0000000000810000-00000000008fffff (4) >> [ +0.000001] 000000007f97f000-000000007f9fefff (4) >> [ +0.000001] 000000007ff00000-000000007fffffff (4) >> [ +0.000002] 0000000000000000-0000000000000fff (2) > > On which arch are you seeing this? There should be one line above these > range printing to tell what they are, like: > > E820 memmap:
Ah this is there too. It's a lot of output, so I took it out of context, apparently.
> 0000000000000000-000000000009a3ff (1) > 000000000009a400-000000000009ffff (2) > 00000000000e0000-00000000000fffff (2) > 0000000000100000-000000006ff83fff (1) > 000000006ff84000-000000007ac50fff (2)
It should all be prefixed like kdump: or kexec: in any way.
>> without actually knowing what that is. >> >> There should be nothing logged if that is not asked for and especially if >> kexec load went fine, right? > > Right. Before this patch, those pr_debug() were already there. You need > enable them to print out like add '#define DEBUG' in *.c file, or enable > the dynamic debugging of the file or function.
I think it's perfectly fine for DEBUG builds to print this out. And many (all major?) distros use dyndbg, so it used to print nothing by default.
> With this patch applied, > you only need specify '-d' when you execute kexec command with > kexec_file load interface, like: > > kexec -s -l -d /boot/vmlinuz-xxxx.img --initrd xxx.img --reuse-cmdline
Perhaps our (SUSE) tooling passes -d? But I am seeing this every time I boot.
No, it does not seem so: load.sh[915]: Starting kdump kernel load; kexec cmdline: /sbin/kexec -p /var/lib/kdump/kernel --append=" loglevel=7 console=tty0 console=ttyS0 video=1920x1080,1024x768,800x600 oops=panic lsm=lockdown,capability,integrity,selinux sysrq=yes reset_devices acpi_no_memhotplug cgroup_disable=memory nokaslr numa=off irqpoll nr_cpus=1 root=kdump rootflags=bind rd.udev.children-max=8 disable_cpu_apicid=0 panic=1" --initrd=/var/lib/kdump/initrd -a
> For kexec_file load, it is not logging if not specifying '-d', unless > you take way to make pr_debug() work in that file.
So is -d detection malfunctioning under some circumstances?
>> Can this be redesigned, please? > > Sure, after making clear what's going on with this, I will try. > >> >> Actually what was wrong on the pr_debug()s? Can you simply turn them on from >> the kernel when -d is passed to kexec instead of all this? > > Joe suggested this during v1 reviewing: > https://lore.kernel.org/all/1e7863ec4e4ab10b84fd0e64f30f8464d2e484a3.camel@perches.com/T/#u > >> >> ... >>> --- a/kernel/kexec_core.c >>> +++ b/kernel/kexec_core.c >>> @@ -52,6 +52,8 @@ atomic_t __kexec_lock = ATOMIC_INIT(0); >>> /* Flag to indicate we are going to kexec a new kernel */ >>> bool kexec_in_progress = false; >>> +bool kexec_file_dbg_print; >> >> Ugh, and a global flag for this? > > Yeah, kexec_file_dbg_print records if '-d' is specified when 'kexec' > command executed. Anything wrong with the global flag?
Global variables are frowned upon. To cite coding style: unless you **really** need them. Here, it looks like you do not.
thanks, -- js suse labs
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