On Mon, Mar 01, 2021 at 08:19:38PM -0800, Florian Fainelli wrote: > BMIPS is one of the few platforms that do change the exception base. > After commit 2dcb39645441 ("memblock: do not start bottom-up allocations > with kernel_end") we started seeing BMIPS boards fail to boot with the > built-in FDT being corrupted. > > Before the cited commit, early allocations would be in the [kernel_end, > RAM_END] range, but after commit they would be within [RAM_START + > PAGE_SIZE, RAM_END]. > > The custom exception base handler that is installed by > bmips_ebase_setup() done for BMIPS5000 CPUs ends-up trampling on the > memory region allocated by unflatten_and_copy_device_tree() thus > corrupting the FDT used by the kernel. > > To fix this, we need to perform an early reservation of the custom > exception that is going to be installed and this needs to happen at > plat_mem_setup() time to ensure that unflatten_and_copy_device_tree() > finds a space that is suitable, away from reserved memory. > > Huge thanks to Serget for analysing and proposing a solution to this > issue. > > Fixes: Fixes: 2dcb39645441 ("memblock: do not start bottom-up allocations with kernel_end") > Debugged-by: Serge Semin <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx> > Reported-by: Kamal Dasu <kdasu.kdev@xxxxxxxxx> > Signed-off-by: Florian Fainelli <f.fainelli@xxxxxxxxx> Acked-by: Roman Gushchin <guro@xxxxxx> Thank you! > --- > Thomas, > > This is intended as a stop-gap solution for 5.12-rc1 and to be picked up > by the stable team for 5.11. We should find a safer way to avoid these > problems for 5.13 maybe. > > arch/mips/bmips/setup.c | 22 ++++++++++++++++++++++ > arch/mips/include/asm/traps.h | 2 ++ > 2 files changed, 24 insertions(+) > > diff --git a/arch/mips/bmips/setup.c b/arch/mips/bmips/setup.c > index 31bcfa4e08b9..0088bd45b892 100644 > --- a/arch/mips/bmips/setup.c > +++ b/arch/mips/bmips/setup.c > @@ -149,6 +149,26 @@ void __init plat_time_init(void) > mips_hpt_frequency = freq; > } > > +static void __init bmips_ebase_reserve(void) > +{ > + phys_addr_t base, size = VECTORSPACING * 64; > + > + switch (current_cpu_type()) { > + default: > + case CPU_BMIPS4350: > + return; > + case CPU_BMIPS3300: > + case CPU_BMIPS4380: > + base = 0x0400; > + break; > + case CPU_BMIPS5000: > + base = 0x1000; > + break; > + } > + > + memblock_reserve(base, size); > +} > + > void __init plat_mem_setup(void) > { > void *dtb; > @@ -169,6 +189,8 @@ void __init plat_mem_setup(void) > > __dt_setup_arch(dtb); > > + bmips_ebase_reserve(); > + > for (q = bmips_quirk_list; q->quirk_fn; q++) { > if (of_flat_dt_is_compatible(of_get_flat_dt_root(), > q->compatible)) { > diff --git a/arch/mips/include/asm/traps.h b/arch/mips/include/asm/traps.h > index 6aa8f126a43d..0ba6bb7f9618 100644 > --- a/arch/mips/include/asm/traps.h > +++ b/arch/mips/include/asm/traps.h > @@ -14,6 +14,8 @@ > #define MIPS_BE_FIXUP 1 /* return to the fixup code */ > #define MIPS_BE_FATAL 2 /* treat as an unrecoverable error */ > > +#define VECTORSPACING 0x100 /* for EI/VI mode */ > + > extern void (*board_be_init)(void); > extern int (*board_be_handler)(struct pt_regs *regs, int is_fixup); > > -- > 2.25.1 >