Re: [PATCH 06/15] powerpc: fadamp: simplify fadump_reserve_crash_area()

[Hari Bathini]

On 01/08/20 3:48 pm, Mike Rapoport wrote:
> On Thu, Jul 30, 2020 at 10:15:13PM +1000, Michael Ellerman wrote:
> > Mike Rapoport <rppt@xxxxxxxxxx> writes:
> > > From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> > >
> > > fadump_reserve_crash_area() reserves memory from a specified base address
> > > till the end of the RAM.
> > >
> > > Replace iteration through the memblock.memory with a single call to
> > > memblock_reserve() with appropriate  that will take care of proper memory
> >                                       ^
> >                                       parameters?
> > > reservation.
> > >
> > > Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> > > ---
> > >   arch/powerpc/kernel/fadump.c | 20 +-------------------
> > >   1 file changed, 1 insertion(+), 19 deletions(-)
> >
> > I think this looks OK to me, but I don't have a setup to test it easily.
> > I've added Hari to Cc who might be able to.
> >
> > But I'll give you an ack in the hope that it works :)
>
> Actually, I did some digging in the git log and the traversal was added
> there on purpose by the commit b71a693d3db3 ("powerpc/fadump: exclude
> memory holes while reserving memory in second kernel")

I was about to comment on the same :)
memblock_reserve() was being used until we ran into the issue talked 
about in the above commit...

> Presuming this is still reqruired I'm going to drop this patch and will

Yeah, it is still required..

> simply replace for_each_memblock() with for_each_mem_range() in v2.

Sounds right.

>   
> > Acked-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> >
> >
> > > diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
> > > index 78ab9a6ee6ac..2446a61e3c25 100644
> > > --- a/arch/powerpc/kernel/fadump.c
> > > +++ b/arch/powerpc/kernel/fadump.c
> > > @@ -1658,25 +1658,7 @@ int __init fadump_reserve_mem(void)
> > >   /* Preserve everything above the base address */
> > >   static void __init fadump_reserve_crash_area(u64 base)
> > >   {
> > > -	struct memblock_region *reg;
> > > -	u64 mstart, msize;
> > > -
> > > -	for_each_memblock(memory, reg) {
> > > -		mstart = reg->base;
> > > -		msize  = reg->size;
> > > -
> > > -		if ((mstart + msize) < base)
> > > -			continue;
> > > -
> > > -		if (mstart < base) {
> > > -			msize -= (base - mstart);
> > > -			mstart = base;
> > > -		}
> > > -
> > > -		pr_info("Reserving %lluMB of memory at %#016llx for preserving crash data",
> > > -			(msize >> 20), mstart);
> > > -		memblock_reserve(mstart, msize);
> > > -	}
> > > +	memblock_reserve(base, memblock_end_of_DRAM() - base);
> > >   }
> > >   
> > >   unsigned long __init arch_reserved_kernel_pages(void)
> > > --
> > > 2.26.2

Thanks
Hari