On Oct 22, 2008, at 10:43 PM, Paul Mackerras wrote:
Paul Mackerras writes:
Milton Miller writes:
Move the flag to 0x5c, 1 word before the secondary cpu entry point at
0x60. Use the copy at address 0 not the one in the base kernel
image to
make it easier on kexec-tools.
Why is it easier on kexec-tools? Doesn't kexec-tools know where it
put the kernel?
The archictecture code calls cross-platform code to identify what is
loaded. It isn't specified if this is a shared mmap or a read into
a buffer.
I'd much rather keep the flag inside the kdump kernel image, rather
than having kexec/kdump start using random fixed locations outside the
new kernel image.
In fact the cliching argument is that when the kernel is loaded by OF
or yaboot, we have no way to tell what will be at location 0x5c,
whereas we know that the word at offset 0x5c in the kernel image will
have been initialized to 0. So we had better put the flag inside the
kernel image.
Well, prom_init will copy the 256 bytes to 0 before the code checks
that location.
However, there is an arguement for using the same code from an epapr
or book-e relocatable, and that would need it at 0. And today
the kexec tool does not do a shared mmap. Since the change has
been made, I will make a new patch for kexec-tools.
milton
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