Re: [RFC] m68k: Enable memtest kernel parameter

[Mike Rapoport <rppt@kernel.org>]

Hi Michael,

On Mon, Sep 13, 2021 at 03:40:12PM +1200, Michael Schmitz wrote:
> Hi Finn,
> 
> On 13/09/21 13:34, Finn Thain wrote:
> > 
> > This appears to work on Aranym, QEMU and the Quadra 630 I have here.
> > It is completely untested on Coldfire etc. I don't even know whether the
> > right memory mappings are in place for this to actually work as intended.
> 
> The comment just above the section from paging_init() in your patch states
> that all physical memory is mapped into kernel virtual address space. I
> don't think that mapping is contiguous though.

early_memtest() operates on physical ranges, so it does not matter what is
the virtual mapping.
 
> > Would someone take a look please?
> > 
> > diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
> > index 6e40f7f29ebc..d87e12b4855b 100644
> > --- a/arch/m68k/Kconfig
> > +++ b/arch/m68k/Kconfig
> > @@ -9,6 +9,7 @@ config M68K
> >  	select ARCH_HAVE_NMI_SAFE_CMPXCHG if RMW_INSNS
> >  	select ARCH_MIGHT_HAVE_PC_PARPORT if ISA
> >  	select ARCH_NO_PREEMPT if !COLDFIRE
> > +	select ARCH_USE_MEMTEST
> >  	select ARCH_WANT_IPC_PARSE_VERSION
> >  	select BINFMT_FLAT_ARGVP_ENVP_ON_STACK
> >  	select DMA_DIRECT_REMAP if HAS_DMA && MMU && !COLDFIRE
> > diff --git a/arch/m68k/mm/motorola.c b/arch/m68k/mm/motorola.c
> > index 3a653f0a4188..d6301a094fc1 100644
> > --- a/arch/m68k/mm/motorola.c
> > +++ b/arch/m68k/mm/motorola.c
> > @@ -455,6 +455,8 @@ void __init paging_init(void)
> > 
> >  	flush_tlb_all();
> > 
> > +	early_memtest(min_addr, max_addr);
> > +
> >  	/*
> >  	 * initialize the bad page table and bad page to point
> >  	 * to a couple of allocated pages
> > 
> 
> I'd rather start that from availmem, not from min_addr ... I'm amazed this
> works - I'd expect the kernel text segment to get trashed by the memory test
> routines.

early_memtest() checks only free memory ranges, i.e. those that were not
memblock_reserve()d, so as long as we reserve the range [min_addr,
availmem] the memtest will skip it.

-- 
Sincerely yours,
Mike.