On 22/07/2019 18:05, Vicente Bergas wrote:

On Monday, July 22, 2019 4:54:41 PM CEST, Marc Zyngier wrote:

quoted

On 22/07/2019 15:31, Vicente Bergas wrote:

quoted

Hi, i have been running linux on rk3399 booted with kexec fine until 5.2
From 5.2 onwards, there are memory corruption issues as reported here:
http://lkml.iu.edu/hypermail/linux/kernel/1906.2/07211.html
kexec has been identified as the principal reason for the issues.

It turns out that kexec has never worked reliably on this platform, ...

Not the most trusted version, but hey, why not...

quoted

 2.- Kexec into v5.2.2
 3.- The kernel reports nothing (earlycon not enabled) and does not 
boot.
The same kernel v5.2.2 works fine when booted without kexec.

Can you please enable earlycon and let us know how far it goes? Your
previous reports hinting at runtime memory corruption, but this seems to
be much more radical...

Details on previous email, but basically, earlycon affects reproducibility.

If it is a runtime memory corruption, what are we hunting for? an issue in
the kernel before kexec or in the kernel after kexec?

The obvious culprit would be DMA devices left running by the first 
kernel scribbling over the second kernel's memory before it's had the 
chance to reset them. Since boot-time memory allocation patterns tend to 
be relatively repeatable for a given platform and kernel configuration, 
"random" may well look a lot less random than you might expect, and it 
wouldn't be unheard of for e.g. the second kernel to mostly allocate its 
dentry cache from the same area the first kernel was mostly putting a 
network Rx descriptor ring.

Robin.

quoted

FWIW, I was able to kexec using 5.2-rcx (for values of x around 6) on a
NanoPC-T4, using a mainline u-boot and firmware.

Thanks,

    M.

Regards,
  Vicenç.


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