[Skiboot] [RFC PATCH] Use two VSX registers to do initial copy of skiboot
stewart at linux.vnet.ibm.com
Fri May 22 15:26:21 AEST 2015
Benjamin Herrenschmidt <benh at kernel.crashing.org> writes:
>> benh, can we use the ipl-params/ipl-params/cec-major-type property to
>> mark "cold" boots as having zeroed memory, and hence skip some of these?
>> I'd like to do this at run time, rather than compile time .
> I don't know whether we have any guarantee from hostboot that we have
> zeroed memory. In fact we don't ... HB itself has left remains behind.
Hrm... that's true.
> We'll need a specific type to represent a sim env. with initial zeroed
> Another bunch of things to consider:
> - Remove useless clearing unconditionally. For example, stacks. We only
> need to clear the cpu_thread structure at the bottom and the last
May be useful to (like mem poisoning) poison the stacks on boot too, may
find something exciting and annoying to debug!
> - Make clearing more efficient. Stewart gave it a good try but what
> about using dcbz ?
yeah, that's probably what we should end up doing. I was just looking
into the implementation that ended up in linux, I'm tempted to try
something with dcbz, yeah. Or, even better, I go to the pub early and
Mikey does it and sends me patches :)
> - Link skiboot at 0x3000_0000 so when pre-loaded there, it doesn't need
> to relocate itself (skip not just copy but also relocation phase).
That could be useful, yeah.
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