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Date: Sun, 8 Aug 2010 22:55:40 -0700
Message-ID: <AANLkTikkRTNU=HWdpvTH-PryeL1mfA12HHFjkXUO8zaU@mail.gmail.com>
Subject: Re: Relocating bootwrapper causes kernel panic
From: Shawn Jin <shawnxjin@gmail.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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Cc: Scott Wood <scottwood@freescale.com>, ppcdev <linuxppc-dev@ozlabs.org>
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>> > >> I think the cause is clear now. But how to fix it? Two questions:
>> > >> 2. If the DTLB miss exception handler is not the right guy to load =
a
>> > >> proper TLB entry, how can I set one entry based on the link_address
>> > >> and the address of the flat dt blob?
>> > >
>> > > Given how early in the boot process it is, it's probably going to ne=
ed
>> > > to be handled specially.
>> >
>> > What APIs can I use to set up DTLBs?
>>
>> I don't think there is one that works on 8xx. =A0You'll could hack up
>> initial_mmu, or else write some C code to insert an 8xx TLB entry.
>
> Yup, I think he just ends up getting out of the initial mapping which is
> smallish on 8xx, no ? Might be worth sticking in one more entry during
> boot...

If CONFIG_PIN_TLB is on, two more entries are pinned down, which gives
16MB mappings. Just curious. Why is there only one entry by default?
what's the trade-off to pin down all 4 entries?

THanks,
-Shawn.