Question about Address Range Validation in Crash Kernel Allocation

[chenhaixiang (A)]

Thank you for your reply!
The kernel version on my machine is kernel-5.10, and the kexec-tools version is kexec-tools-2.0.27. 
However, my issue seems to be a bit different. On my machine, I can see the crashkernel memory segment in /proc/iomem. However, for some reason, within the address range allocated for crashkernel, there is also a segment marked as 'Reserved' (I'm not sure who marked it). In this scenario, kexec-tools calculates the CRASH MEMORY RANGES incorrectly.
```
cat /proc/iomem
2d4fd058-58ffffff : System RAM
  49000000-58ffffff : Crash kernel
    53cbd000-53ccffff : Reserved
```
I'm not sure if the crashkernel memory segment should not include other markings, and if not supported, whether kexec-tools should raise an error.
Thanks
Chen Haixiang
----------
On 03/19/24 at 9:38qm, Baoquan He wrote:
> Hi,
> 
> On 03/18/24 at 12:00pm, chenhaixiang (A) wrote:
> > Dear kexec Community Members,
> >
> > I encountered an issue while using kexec-tools on my x86_64 machine.
> > When there is a segment marked as 'reserved' within the memory range
> allocated for the crash kernel in /proc/iomem,the output appears as follows:
> > 2d4fd058-60efefff : System RAM
> >   2d4fd058-58ffffff : System RAM
> >     49000000-58ffffff : Crash kernel
> >       53cbd000-53ccffff : Reserved
> 
> What kernel are you using? the version of kernel, and kexec-tools?
> 
> If you are testing on the latest mainline kernel, you could meet the issue Dave
> have met and fixed in below patch:
> 
> [PATCH] x86/kexec: do not update E820 kexec table for setup_data
> https://lore.kernel.org/all/ZeZ2Kos-OOZNSrmO@darkstar.users.ipa.redhat.com/
> T/#u
> 
> Thanks
> Baoquan
> 
> >
> > The crash_memory_range array will encounter incorrect address ranges:
> > CRASH MEMORY RANGES
> > 000000002d4fd058-0000000048ffffff (0)
> > 0000000053cbd000-0000000048ffffff (1)
> > 0000000059000000-0000000053ccffff (0)
> >
> > Read the code, I noticed that the get_crash_memory_ranges() function
> invokes exclude_region() to handle the splitting of memory regions, but it seems
> unable to properly handle the scenario described above.
> > The code logic is as follows:
> > ...
> > 	if (start < mend && end > mstart) {
> > 		if (start != mstart && end != mend) {
> > 			/* Split memory region */
> > 			crash_memory_range[i].end = start - 1;
> > 			temp_region.start = end + 1;
> > 			temp_region.end = mend;
> > 			temp_region.type = RANGE_RAM;
> > 			tidx = i+1;
> > 		} else if (start != mstart)
> > 			crash_memory_range[i].end = start - 1;
> > 		else
> > 			crash_memory_range[i].start = end + 1;
> > 	}
> > ...
> > If start < mstart < mend < end, resulting in crash_memory_range[i].end
> becoming less than crash_memory_range[i].start, leading to incorrect address
> ranges.
> > I would like to know if this behavior is reasonable and whether it is necessary to
> validate the address ranges for compliance at the end.
> >
> > Thank you for your time and assistance.
> >
> > Chen Haixiang
> >
> > _______________________________________________
> > kexec mailing list
> > kexec at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kexec
> >