Re: [PATCH] Revert "arm: bootm: Disable LMB reservation for command line and board info on arm64"

[Tom Rini <trini@konsulko.com>]

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On Mon, Aug 02, 2021 at 01:54:57PM +0200, Jan Kiszka wrote:
> On 02.08.21 13:38, Marek Vasut wrote:
> > On 8/2/21 1:36 PM, Jan Kiszka wrote:
> >> On 02.08.21 12:48, Marek Vasut wrote:
> >>> On 8/2/21 11:37 AM, Jan Kiszka wrote:
> >>>> On 02.08.21 02:54, Marek Vasut wrote:
> >>>>> On 7/29/21 6:58 PM, Tom Rini wrote:
> >>>>>
> >>>>> [...]
> >>>>>
> >>>>>>>> so when did rcar3 introduce something there that shouldn't be
> >>>>>>>> reserved?  And you had phrased this to me on IRC as about reserving
> >>>>>>>> spot
> >>>>>>>> for ATAGS, and that not being needed of course on arm64.  But
> >>>>>>>> that's
> >>>>>>>> not
> >>>>>>>> what's going on.  Perhaps the answer is that rcar3 needs to
> >>>>>>>> introduce a
> >>>>>>>> board_lmb_reserve to free the normal arch one and provide whatever
> >>>>>>>> more
> >>>>>>>> narrow scope it needs.
> >>>>>>>
> >>>>>>> Based on the commit message 2359fa7a878 ("arm: bootm: Disable LMB
> >>>>>>> reservation for command line and board info on arm64") , this is
> >>>>>>> about ATAGS
> >>>>>>> and we really don't need to reserve those on arm64.
> >>>>>>
> >>>>>> Commit 2359fa7a878 disables the entire arch_lmb_reserve function on
> >>>>>> aarch64, yes.  I assumed when we had talked that it was a small area
> >>>>>> being set aside and perhaps mis-recalled that ATAGS tended to live at
> >>>>>> DDR_BASE + 0x800 or so.
> >>>>>
> >>>>> That arch_lmb_reserve() is responsible for reserving architecture
> >>>>> specific memory. On arm32 it is ATAGS, on arm64 it is nothing as
> >>>>> far as
> >>>>> I can tell (and see below regarding the TLB).
> >>>>>
> >>>>>> This reservation is not at that spot, and a lot
> >>>>>> more than that.
> >>>>>
> >>>>> Can you please elaborate on this "lot more" part ? Because as much
> >>>>> as I
> >>>>> studied the reservation code, the "lot more" was ATAGS on arm32 and
> >>>>> nothing on arm64.
> >>>>
> >>>> See my commit log.
> >>>
> >>> This is not particularly useful answer, considering the commit log says:
> >>> "lot of crucial things", "Possibly more", "likely also on other boards"
> >>> and other opaque statements. But really, the problem so far happens on
> >>> one K3 board.
> >>
> >> "Such things are the page table (tlb_addr),
> >> relocated U-Boot and the active stack."
> > 
> > Please read the rest of my answer, I don't believe the TLB should be
> > reserved at all. DTTO for the stack. If you think otherwise, please
> > explain why.
> 
> Marek, I've provided you with three generic examples of active memory
> blocks that are relevant while U-Boot is allocating from and also
> filling that LMB. Please follow those cases and explain to us why they
> aren't active - or at least prove why they are specific the k3 (for
> which I found no traces).
> 
> And stop following the TLB topic for now. That was only my first guess.
> The actual crash I'm seeing on my board come from plain code
> overwriting. It could have been TLB as well. It could also have been the
> stack. All those become unprotected via your reservation removal.

Jan, one thing I didn't see before is, are you also using
include/configs/ti_armv7_common.h in the end, like the K3 reference
platforms, and if not are you setting bootm_size in your environment?  I
have one more idea on why this fails on your board but not Marek's.
Thanks.

-- 
Tom

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