Re: [PATCH 0/8] implement "memmap on memory" feature on s390

[David Hildenbrand]

On 21.11.23 14:21, Sumanth Korikkar wrote:
> On Tue, Nov 21, 2023 at 02:13:22PM +0100, Sumanth Korikkar wrote:
> > Approach 2:
> > ===========
> > Shouldnt kasan zero shadow mapping performed first before
> > accessing/initializing memmap via page_init_poisining()?  If that is
> > true, then it is a problem for all architectures and should could be
> > fixed like:
> >
> >
> > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> > index 7a5fc89a8652..eb3975740537 100644
> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
> > @@ -1093,6 +1093,7 @@ int mhp_init_memmap_on_memory(unsigned long pfn, unsigned long nr_pages,
> >   	if (ret)
> >   		return ret;
> >
> > +	page_init_poison(pfn_to_page(pfn), sizeof(struct page) * nr_pages);
> >   	move_pfn_range_to_zone(zone, pfn, nr_pages, NULL, MIGRATE_UNMOVABLE);
> >
> >   	for (i = 0; i < nr_pages; i++)
> > diff --git a/mm/sparse.c b/mm/sparse.c
> > index 77d91e565045..4ddf53f52075 100644
> > --- a/mm/sparse.c
> > +++ b/mm/sparse.c
> > @@ -906,8 +906,11 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
> >   	/*
> >   	 * Poison uninitialized struct pages in order to catch invalid flags
> >   	 * combinations.
> > +	 * For altmap, do this later when onlining the memory, as it might
> > +	 * not be accessible at this point.
> >   	 */
> > -	page_init_poison(memmap, sizeof(struct page) * nr_pages);
> > +	if (!altmap)
> > +		page_init_poison(memmap, sizeof(struct page) * nr_pages);
> >
> >   	ms = __nr_to_section(section_nr);
> >   	set_section_nid(section_nr, nid);
> >
> >
> >
> > Also, if this approach is taken, should page_init_poison() be performed
> > with cond_resched() as mentioned in commit d33695b16a9f
> > ("mm/memory_hotplug: poison memmap in remove_pfn_range_from_zone()") ?
>
> Sorry, wrong commit id.
>
> should page_init_poison() be performed with cond_resched() as mentioned in
> Commit b7e3debdd040 ("mm/memory_hotplug.c: fix false softlockup
> during pfn range removal") ?

I think people are currently looking into removing all that cond_resched():

https://lore.kernel.org/all/20231107230822.371443-29-ankur.a.arora@xxxxxxxxxx/T/#mda52da685a142bec9607625386b0b660e5470abe
--
Cheers,

David / dhildenb