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

Hari Bathini
2020-08-01T15:54:42Z

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@kernel.org> writes:
>>> From: Mike Rapoport <rppt@linux.ibm.com>
>>>
>>> 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@linux.ibm.com>
>>> ---
>>> 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@ellerman.id.au>
>>
>>
>>> 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