powerpc/mm_iommu: Allow pinning large regions

When called with vmas_arg==NULL, get_user_pages_longterm() allocates
an array of nr_pages*8 which can easily get greater that the max order,
for example, registering memory for a 256GB guest does this and fails
in __alloc_pages_nodemask().

This adds a loop over chunks of entries to fit the max order limit.

Fixes: 678e174c4c16 ("powerpc/mm/iommu: allow migration of cma allocated pages during mm_iommu_do_alloc", 2019-03-05)
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 20 insertions, 4 deletions

diff --git a/arch/powerpc/mm/mmu_context_iommu.c b/arch/powerpc/mm/mmu_context_iommu.c
index 9d9be850f8c2..8330f135294f 100644
--- a/arch/powerpc/mm/mmu_context_iommu.c
+++ b/arch/powerpc/mm/mmu_context_iommu.c
@@ -98,6 +98,7 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
         struct mm_iommu_table_group_mem_t *mem, *mem2;
         long i, ret, locked_entries = 0, pinned = 0;
         unsigned int pageshift;
+        unsigned long entry, chunk;
 
         if (dev_hpa == MM_IOMMU_TABLE_INVALID_HPA) {
                 ret = mm_iommu_adjust_locked_vm(mm, entries, true);
@@ -134,11 +135,26 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
         }
 
         down_read(&mm->mmap_sem);
-        ret = get_user_pages_longterm(ua, entries, FOLL_WRITE, mem->hpages, NULL);
+        chunk = (1UL << (PAGE_SHIFT + MAX_ORDER - 1)) /
+                        sizeof(struct vm_area_struct *);
+        chunk = min(chunk, entries);
+        for (entry = 0; entry < entries; entry += chunk) {
+                unsigned long n = min(entries - entry, chunk);
+
+                ret = get_user_pages_longterm(ua + (entry << PAGE_SHIFT), n,
+                                FOLL_WRITE, mem->hpages + entry, NULL);
+                if (ret == n) {
+                        pinned += n;
+                        continue;
+                }
+                if (ret > 0)
+                        pinned += ret;
+                break;
+        }
         up_read(&mm->mmap_sem);
-        pinned = ret > 0 ? ret : 0;
-        if (ret != entries) {
-                ret = -EFAULT;
+        if (pinned != entries) {
+                if (!ret)
+                        ret = -EFAULT;
                 goto free_exit;
         }