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

[Pierre-Clément Tosi]

Hi Fabio,

On Tue, Mar 19, 2024 at 09:13:12AM -0300, Fabio Estevam wrote:
> Hi Pierre,
> 
> On Tue, Mar 19, 2024 at 8:39 AM Pierre-Clément Tosi <ptosi at google.com> wrote:
> 
> > This means gd->arch.tlb_addr pointing to the live PTs during setup_pgtables().
> >
> > In arch/arm/cpu/armv8, setup_all_pgtables() runs with SCTLR_ELx.M unset.
> >
> > In arch/arm/cpu/armv8/fsl-layerscape, setup_pgtables() is called twice:
> >
> >  - early_mmu_setup() calls it with SCTLR_ELx.M unset;
> >  - final_mmu_setup() overwrites gd->arch.tlb_addr before calling it iff
> >    CFG_SYS_MEM_RESERVE_SECURE is defined i.e. if CONFIG_SYS_SOC="fsl-layerscape"
> >    so that <asm/arch-fsl-layerscape/config.h> gets auto-included through
> >    <include/config.h>.
> >
> > So can CONFIG_FSL_LAYERSCAPE be set while CONFIG_SYS_SOC != "fsl-layerscape"?
> 
> No, this cannot happen.

Thanks for confirming.

For clarity, it might then make sense to drop that #ifdef in final_mmu_setup().

> Only the following Layerscape SoCs select CONFIG_FSL_LAYERSCAPE
> in arch/arm/cpu/armv8/fsl-layerscape/Kconfig:
> LS1012A, LS1028A, LS1043A, LS1046A, LS1088A, LS2080A, LX2162A and LX2160A
> 
> I saw the original boot problem with the i.MX8QX.
> 
> The i.MX8QX is part of the i.MX family, not the Layerscape family.

Sure.

To be clear, the concern here was that split_block() doesn't perform what the
CPU architecture requires when modifying page tables that the MMU is using and
the question therefore was: can setup_pgtables() be called on such live PTs?

For most AArch64 U-Boot ports (including the i.MX family), the answer is trivial
because they use the arch code i.e. setup_all_pgtables(). However, as
fsl-layerscape re-implements mmu_setup(), it had to be looked at separately,
hence my question, which you answered above.

HTH,

-- 
Pierre