With virtio-mem, we actually want to remove memory again.

Cc: Martin Schwidefsky <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: [email protected]
Signed-off-by: David Hildenbrand <[email protected]>
---
 arch/s390/mm/init.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 3fa3e5323612..7202344d0eae 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -242,12 +242,18 @@ int arch_add_memory(int nid, u64 start, u64 size, struct 
vmem_altmap *altmap,
 #ifdef CONFIG_MEMORY_HOTREMOVE
 int arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap)
 {
-       /*
-        * There is no hardware or firmware interface which could trigger a
-        * hot memory remove on s390. So there is nothing that needs to be
-        * implemented.
-        */
-       return -EBUSY;
+       const unsigned long start_pfn = start >> PAGE_SHIFT;
+       const unsigned long nr_pages = size >> PAGE_SHIFT;
+       struct page *page = pfn_to_page(start_pfn);
+       struct zone *zone;
+       int ret;
+
+       zone = page_zone(page);
+       ret = __remove_pages(zone, start_pfn, nr_pages, altmap);
+       WARN_ON_ONCE(ret);
+       vmem_remove_mapping(start, size);
+
+       return ret;
 }
 #endif
 #endif /* CONFIG_MEMORY_HOTPLUG */
-- 
2.17.0

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