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

[Tom Rini]

On Mon, Aug 02, 2021 at 04:03:01PM +0200, Jan Kiszka wrote:
> On 02.08.21 15:04, Tom Rini wrote:
> > 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.
> 
> We are including that header but we didn't use DEFAULT_LINUX_BOOT_ENV,
> in fact. That left bootm_size undefined. Can you explain the impact?

I suspect the answer here is that Marek does not see this problem
because on R-Car bootm_size is set to 0x10000000 and so no relocation of
the device tree / kernel / initrd happens to overwrite the running
U-Boot and blow everything up.  If you don't revert this, and do set
bootm_size does everything work?  Marek, if you unset bootm_size, do you
see failure?  Thanks!

-- 
Tom
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 659 bytes
Desc: not available
URL: <https://lists.denx.de/pipermail/u-boot/attachments/20210802/415c6be3/attachment.sig>