Re: [Patch v3] mm/memblock: remove empty dummy entry

[Wei Yang <richard.weiyang@gmail.com>]

On Thu, Jun 20, 2024 at 07:34:06PM -0700, Guenter Roeck wrote:
>On 6/20/24 18:07, Wei Yang wrote:
>> On Thu, Jun 20, 2024 at 02:58:17PM -0700, Guenter Roeck wrote:
>> > Hi,
>> > 
>> > On Fri, Apr 05, 2024 at 01:58:21AM +0000, Wei Yang wrote:
>> > > The dummy entry is introduced in the initial implementation of lmb in
>> > > commit 7c8c6b9776fb ("powerpc: Merge lmb.c and make MM initialization
>> > > use it.").
>> > > 
>> > > As the comment says the empty dummy entry is to simplify the code.
>> > > 
>> > > 	/* Create a dummy zero size LMB which will get coalesced away later.
>> > >           * This simplifies the lmb_add() code below...
>> > >           */
>> > > 
>> > > While current code is reimplemented by Tejun in commit 784656f9c680
>> > > ("memblock: Reimplement memblock_add_region()"). This empty dummy entry
>> > > seems not benefit the code any more.
>> > > 
>> > > Let's remove it.
>> > > 
>> > > Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
>> > > CC: Paul Mackerras <paulus@ozlabs.org>
>> > > CC: Tejun Heo <tj@kernel.org>
>> > > CC: Mike Rapoport <rppt@kernel.org>
>> > > 
>> > 
>> > With this patch in linux-next, all microblaze qemu images fail to boot. Reverting it
>> > fixes the problem.
>> > 
>> > Bisect log is attached for reference.
>> > 
>> 
>> Thanks for the reporting.
>> 
>> Would you mind running the test to take a look?
>> 
>> It is in tools/testing/memblock. Simply make and ./main.
>> 

This is a user-space test case, would you mind running it with this commit
applied?

>
>This is a silent failure. There is no console output, so the image crashes
>before it gets to that point.
>
>Building microblaze:petalogix-s3adsp1800:initrd ... running ................R............. failed (silent)
>------------
>qemu log:
>qemu-system-microblaze: terminating on signal 15 from pid 2343410 (/bin/bash)
>

Would you mind add kernel parameter memblock=debug without the commit applied?
If my understanding is correct, you can bootup without this commit, right?

>Guenter

-- 
Wei Yang
Help you, Help me