s390/mm: allocate vmemmap pages from self-contained memory range

Allocate memory map (struct pages array) from the hotplugged memory
range, rather than using system memory. The change addresses the issue
where standby memory, when configured to be much larger than online
memory, could potentially lead to ipl failure due to memory map
allocation from online memory. For example, 16MB of memory map
allocation is needed for a memory block size of 1GB and when standby
memory is configured much larger than online memory, this could lead to
ipl failure.

To address this issue, the solution involves introducing "memmap on
memory" using the vmem_altmap structure on s390. Architectures that
want to implement it should pass the altmap to the vmemmap_populate()
function and its associated callchain. This enhancement is discussed in
commit 4b94ffdc4163 ("x86, mm: introduce vmem_altmap to augment
vmemmap_populate()")

Provide "memmap on memory" support for s390 by passing the altmap in
vmemmap_populate() and its callchain. The allocation path is described
as follows:
* When altmap is NULL in vmemmap_populate(), memory map allocation
occurs using the existing vmemmap_alloc_block_buf().
* When altmap is not NULL in vmemmap_populate(), memory map allocation
still uses vmemmap_alloc_block_buf(), but this function internally
calls altmap_alloc_block_buf().

For deallocation, the process is outlined as follows:
* When altmap is NULL in vmemmap_free(), memory map deallocation happens
through free_pages().
* When altmap is not NULL in vmemmap_free(), memory map deallocation
occurs via vmem_altmap_free().

While memory map allocation is primarily handled through the
self-contained memory map range, there might still be a small amount of
system memory allocation required for vmemmap pagetables. To mitigate
this impact, this feature will be limited to machines with EDAT1
support.

Link: https://lkml.kernel.org/r/[e-mail]
Reviewed-by: Gerald Schaefer <[e-mail]>
Signed-off-by: Sumanth Korikkar <[e-mail]>
Cc: Alexander Gordeev <[e-mail]>
Cc: Aneesh Kumar K.V <[e-mail]>
Cc: Anshuman Khandual <[e-mail]>
Cc: David Hildenbrand <[e-mail]>
Cc: Heiko Carstens <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Oscar Salvador <[e-mail]>
Cc: Vasily Gorbik <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

arch/s390/mm/init.c

···
 	unsigned long size_pages = PFN_DOWN(size);
 	int rc;
 
-	if (WARN_ON_ONCE(params->altmap))
-		return -EINVAL;
-
 	if (WARN_ON_ONCE(params->pgprot.pgprot != PAGE_KERNEL.pgprot))
 		return -EINVAL;
 

arch/s390/mm/vmem.c

···
 	return memblock_alloc(size, size);
 }
 
-static void vmem_free_pages(unsigned long addr, int order)
+static void vmem_free_pages(unsigned long addr, int order, struct vmem_altmap *altmap)
 {
+	if (altmap) {
+		vmem_altmap_free(altmap, 1 << order);
+		return;
+	}
 	/* We don't expect boot memory to be removed ever. */
 	if (!slab_is_available() ||
 	    WARN_ON_ONCE(PageReserved(virt_to_page((void *)addr))))
···
 
 /* __ref: we'll only call vmemmap_alloc_block() via vmemmap_populate() */
 static int __ref modify_pte_table(pmd_t *pmd, unsigned long addr,
-				  unsigned long end, bool add, bool direct)
+				  unsigned long end, bool add, bool direct,
+				  struct vmem_altmap *altmap)
 {
 	unsigned long prot, pages = 0;
 	int ret = -ENOMEM;
···
 			if (pte_none(*pte))
 				continue;
 			if (!direct)
-				vmem_free_pages((unsigned long) pfn_to_virt(pte_pfn(*pte)), 0);
+				vmem_free_pages((unsigned long)pfn_to_virt(pte_pfn(*pte)), get_order(PAGE_SIZE), altmap);
 			pte_clear(&init_mm, addr, pte);
 		} else if (pte_none(*pte)) {
 			if (!direct) {
-				void *new_page = vmemmap_alloc_block(PAGE_SIZE, NUMA_NO_NODE);
+				void *new_page = vmemmap_alloc_block_buf(PAGE_SIZE, NUMA_NO_NODE, altmap);
 
 				if (!new_page)
 					goto out;
···
 
 /* __ref: we'll only call vmemmap_alloc_block() via vmemmap_populate() */
 static int __ref modify_pmd_table(pud_t *pud, unsigned long addr,
-				  unsigned long end, bool add, bool direct)
+				  unsigned long end, bool add, bool direct,
+				  struct vmem_altmap *altmap)
 {
 	unsigned long next, prot, pages = 0;
 	int ret = -ENOMEM;
···
 				if (IS_ALIGNED(addr, PMD_SIZE) &&
 				    IS_ALIGNED(next, PMD_SIZE)) {
 					if (!direct)
-						vmem_free_pages(pmd_deref(*pmd), get_order(PMD_SIZE));
+						vmem_free_pages(pmd_deref(*pmd), get_order(PMD_SIZE), altmap);
 					pmd_clear(pmd);
 					pages++;
 				} else if (!direct && vmemmap_unuse_sub_pmd(addr, next)) {
-					vmem_free_pages(pmd_deref(*pmd), get_order(PMD_SIZE));
+					vmem_free_pages(pmd_deref(*pmd), get_order(PMD_SIZE), altmap);
 					pmd_clear(pmd);
 				}
 				continue;
···
 				 * page tables since vmemmap_populate gets
 				 * called for each section separately.
 				 */
-				new_page = vmemmap_alloc_block(PMD_SIZE, NUMA_NO_NODE);
+				new_page = vmemmap_alloc_block_buf(PMD_SIZE, NUMA_NO_NODE, altmap);
 				if (new_page) {
 					set_pmd(pmd, __pmd(__pa(new_page) | prot));
 					if (!IS_ALIGNED(addr, PMD_SIZE) ||
···
 				vmemmap_use_sub_pmd(addr, next);
 			continue;
 		}
-		ret = modify_pte_table(pmd, addr, next, add, direct);
+		ret = modify_pte_table(pmd, addr, next, add, direct, altmap);
 		if (ret)
 			goto out;
 		if (!add)
···
 	for (i = 0; i < PTRS_PER_PMD; i++, pmd++)
 		if (!pmd_none(*pmd))
 			return;
-	vmem_free_pages(pud_deref(*pud), CRST_ALLOC_ORDER);
+	vmem_free_pages(pud_deref(*pud), CRST_ALLOC_ORDER, NULL);
 	pud_clear(pud);
 }
 
 static int modify_pud_table(p4d_t *p4d, unsigned long addr, unsigned long end,
-			    bool add, bool direct)
+			    bool add, bool direct, struct vmem_altmap *altmap)
 {
 	unsigned long next, prot, pages = 0;
 	int ret = -ENOMEM;
···
 		} else if (pud_large(*pud)) {
 			continue;
 		}
-		ret = modify_pmd_table(pud, addr, next, add, direct);
+		ret = modify_pmd_table(pud, addr, next, add, direct, altmap);
 		if (ret)
 			goto out;
 		if (!add)
···
 		if (!pud_none(*pud))
 			return;
 	}
-	vmem_free_pages(p4d_deref(*p4d), CRST_ALLOC_ORDER);
+	vmem_free_pages(p4d_deref(*p4d), CRST_ALLOC_ORDER, NULL);
 	p4d_clear(p4d);
 }
 
 static int modify_p4d_table(pgd_t *pgd, unsigned long addr, unsigned long end,
-			    bool add, bool direct)
+			    bool add, bool direct, struct vmem_altmap *altmap)
 {
 	unsigned long next;
 	int ret = -ENOMEM;
···
 				goto out;
 			p4d_populate(&init_mm, p4d, pud);
 		}
-		ret = modify_pud_table(p4d, addr, next, add, direct);
+		ret = modify_pud_table(p4d, addr, next, add, direct, altmap);
 		if (ret)
 			goto out;
 		if (!add)
···
 		if (!p4d_none(*p4d))
 			return;
 	}
-	vmem_free_pages(pgd_deref(*pgd), CRST_ALLOC_ORDER);
+	vmem_free_pages(pgd_deref(*pgd), CRST_ALLOC_ORDER, NULL);
 	pgd_clear(pgd);
 }
 
 static int modify_pagetable(unsigned long start, unsigned long end, bool add,
-			    bool direct)
+			    bool direct, struct vmem_altmap *altmap)
 {
 	unsigned long addr, next;
 	int ret = -ENOMEM;
···
 				goto out;
 			pgd_populate(&init_mm, pgd, p4d);
 		}
-		ret = modify_p4d_table(pgd, addr, next, add, direct);
+		ret = modify_p4d_table(pgd, addr, next, add, direct, altmap);
 		if (ret)
 			goto out;
 		if (!add)
···
 	return ret;
 }
 
-static int add_pagetable(unsigned long start, unsigned long end, bool direct)
+static int add_pagetable(unsigned long start, unsigned long end, bool direct,
+			 struct vmem_altmap *altmap)
 {
-	return modify_pagetable(start, end, true, direct);
+	return modify_pagetable(start, end, true, direct, altmap);
 }
 
-static int remove_pagetable(unsigned long start, unsigned long end, bool direct)
+static int remove_pagetable(unsigned long start, unsigned long end, bool direct,
+			    struct vmem_altmap *altmap)
 {
-	return modify_pagetable(start, end, false, direct);
+	return modify_pagetable(start, end, false, direct, altmap);
 }
 
 /*
···
 static int vmem_add_range(unsigned long start, unsigned long size)
 {
 	start = (unsigned long)__va(start);
-	return add_pagetable(start, start + size, true);
+	return add_pagetable(start, start + size, true, NULL);
 }
 
 /*
···
 static void vmem_remove_range(unsigned long start, unsigned long size)
 {
 	start = (unsigned long)__va(start);
-	remove_pagetable(start, start + size, true);
+	remove_pagetable(start, start + size, true, NULL);
 }
 
 /*
···
 
 	mutex_lock(&vmem_mutex);
 	/* We don't care about the node, just use NUMA_NO_NODE on allocations */
-	ret = add_pagetable(start, end, false);
+	ret = add_pagetable(start, end, false, altmap);
 	if (ret)
-		remove_pagetable(start, end, false);
+		remove_pagetable(start, end, false, altmap);
 	mutex_unlock(&vmem_mutex);
 	return ret;
 }
···
 		  struct vmem_altmap *altmap)
 {
 	mutex_lock(&vmem_mutex);
-	remove_pagetable(start, end, false);
+	remove_pagetable(start, end, false, altmap);
 	mutex_unlock(&vmem_mutex);
 }