verify kdump using patchset: support reserving crashkernel above 4G on arm64 kdump

[adamliyi]

Test kdump using latest upstream linus tree.

1. set kernel option: crashkernel=4G. Boot kernel and dmesg | grep crashkernel. Very likely crashkernel memory cannot be reserved, since by default on arm64 crashkernel will allocate bellow 4G.
2. Apply upstream patch: [PATCH v21 0/5] support reserving crashkernel above 4G on arm64 kdump: https://lkml.org/lkml/2022/2/26/350
3. Try option: crashkernel=4G
4. Try option: crashkernel=4G crashkernel=16M,low
5. Try kdump if crashkernel memory can be reserved.

Before the patch, these option should fail:

`crashkernel=4G`  // fail. by default kernel try to allocate bellow 4GB
`crashkernel=4G crashkernel=16M,low` //fail, low option not supported

After the patch, bellow option should be supported:

The test cases are as follows: (Please update the kexec tool to the latest version)
1) crashkernel=4G						//high=4G, low=256M
2) crashkernel=4G crashkernel=512M,high crashkernel=512M,low	//high=4G, low=256M, high and low are ignored
3) crashkernel=4G crashkernel=512M,high				//high=4G, low=256M, high is ignored
4) crashkernel=4G crashkernel=512M,low				//high=4G, low=256M, low is ignored
5) crashkernel=4G@0xe0000000					//high=0G, low=0M, cannot allocate, failed
6) crashkernel=512M						//high=0G, low=512M
7) crashkernel=128M						//high=0G, low=128M
8) crashkernel=512M@0xde000000		//512M@3552M		//high=0G, low=512M
9) crashkernel=4G,high						//high=4G, low=256M
a) crashkernel=4G,high crashkernel=512M,low			//high=4G, low=512M
b) crashkernel=512M,high crashkernel=128M,low			//high=512M, low=128M
c) crashkernel=128M,high					//high=128M, low=256M
d) crashkernel=512M,low						//high=0G, low=0M, invalid
e) crashkernel=512M,high crashkernel=0,low			//high=512M, low=0M
f) crashkernel=4G,high crashkernel=ab,low			//high=0G, low=0M, invalid

[bobolmw]

Test result based on latest linus master branch in ampere platform:

1. without patch: cannot allocate memory
2. with option 'crashkernel=4G', kdump works, 256MB low memory reserverd, dump file generated
3. with option 'crashkernel=4G crashkernel=512MB,low', kdump works, 256MB low memory reserverd, dump file generated

[adamliyi]

Updated on 05/05/2022: patch backported to 5.15 Longterm kernel: #165

[adamliyi]

https://lore.kernel.org/linux-arm-kernel/[email protected]/
V22 of the patch has been posted on 2022-04-14, will keep testing and tracking.