[PATCH] arm64: Fix map_range() not splitting mapped blocks

[Hiago De Franco]

On Mon, Mar 18, 2024 at 04:46:55PM -0300, Fabio Estevam wrote:
> Hi Pierre,
> 
> On Mon, Mar 18, 2024 at 4:35 PM Pierre-Clément Tosi <ptosi at google.com> wrote:
> >
> > The implementation of map_range() creates the requested mapping by
> > walking the page tables, iterating over multiple PTEs and/or descending
> > into existing table mappings as needed. When doing so, it assumes any
> > pre-existing valid PTE to be a table mapping. This assumption is wrong
> > if the platform code attempts to successively map two overlapping ranges
> > where the latter intersects a block mapping created for the former.
> >
> > As a result, map_range() treats the existing block mapping as a table
> > mapping and descends into it i.e. starts interpreting the
> > previously-mapped range as an array of PTEs, writing to them and
> > potentially even descending further (extra fun with MMIO ranges!).
> >
> > Instead, pass any valid non-table mapping to split_block(), which
> > ensures that it actually was a block mapping (calls panic() otherwise)
> > before splitting it.
> >
> > Fixes: 41e2787f5ec4 ("arm64: Reduce add_map() complexity")
> > Signed-off-by: Pierre-Clément Tosi <ptosi at google.com>
> 
> This fixes the boot regression on colibri-imx8x.
> 
> Thanks a lot for your fix!
> 
> Tested-by: Fabio Estevam <festevam at gmail.com>

Tested-by: Hiago De Franco <hiago.franco at toradex.com> # Toradex Verdin AM62

On Sat, Mar 23, 2024 at 10:34:54AM -0400, Tom Rini wrote:
> On Fri, Mar 22, 2024 at 04:33:03PM -0300, Fabio Estevam wrote:
> > On Fri, Mar 22, 2024 at 4:31 PM Fabio Estevam <festevam at gmail.com> wrote:
> > 
> > > As Pierre's explanation addresses Marc's concern,
> > > do you think this can go to 2024.01 to fix the boot regression on imx8qxp/8qm?
> > 
> > I meant 2024.04, sorry.
> 
> How much testing has this seen outside of imx?

Tom, I tested with the AM62 TI arm processor (Toradex Verdin AM62) and
it works fine.

U-Boot 2024.04-rc4-00001-g5db2e36c8e97 (Mar 25 2024 - 17:28:20 -0300)

SoC:   AM62X SR1.0 HS-FS
DRAM:  1 GiB
Core:  138 devices, 29 uclasses, devicetree: separate
MMC:   mmc at fa10000: 0, mmc at fa00000: 1
Loading Environment from MMC... OK
In:    serial at 2800000
Out:   serial at 2800000
Err:   serial at 2800000
Model: Toradex 0074 Verdin AM62 Dual 1GB IT V1.1A
Serial#: 15133548
Carrier: Toradex Dahlia V1.1C, Serial# 10952631

I've added my Tested-by as well.

> 
> -- 
> Tom

Best Regards,

Hiago.