diff mbox series

[v8,4/4] powerpc/mm/iommu: Allow large IOMMU page size only for hugetlb backing

Message ID 20190227144736.5872-5-aneesh.kumar@linux.ibm.com (mailing list archive)
State New, archived
Headers show
Series mm/kvm/vfio/ppc64: Migrate compound pages out of CMA region | expand

Commit Message

Aneesh Kumar K.V Feb. 27, 2019, 2:47 p.m. UTC
THP pages can get split during different code paths. An incremented reference
count does imply we will not split the compound page. But the pmd entry can be
converted to level 4 pte entries. Keep the code simpler by allowing large
IOMMU page size only if the guest ram is backed by hugetlb pages.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---
 arch/powerpc/mm/mmu_context_iommu.c | 24 +++++++-----------------
 1 file changed, 7 insertions(+), 17 deletions(-)
diff mbox series

Patch

diff --git a/arch/powerpc/mm/mmu_context_iommu.c b/arch/powerpc/mm/mmu_context_iommu.c
index 85b4e9f5c615..e7a9c4f6bfca 100644
--- a/arch/powerpc/mm/mmu_context_iommu.c
+++ b/arch/powerpc/mm/mmu_context_iommu.c
@@ -98,8 +98,6 @@  static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
 	struct mm_iommu_table_group_mem_t *mem;
 	long i, ret, locked_entries = 0;
 	unsigned int pageshift;
-	unsigned long flags;
-	unsigned long cur_ua;
 
 	mutex_lock(&mem_list_mutex);
 
@@ -167,22 +165,14 @@  static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
 	for (i = 0; i < entries; ++i) {
 		struct page *page = mem->hpages[i];
 
-		cur_ua = ua + (i << PAGE_SHIFT);
-		if (mem->pageshift > PAGE_SHIFT && PageCompound(page)) {
-			pte_t *pte;
+		/*
+		 * Allow to use larger than 64k IOMMU pages. Only do that
+		 * if we are backed by hugetlb.
+		 */
+		if ((mem->pageshift > PAGE_SHIFT) && PageHuge(page)) {
 			struct page *head = compound_head(page);
-			unsigned int compshift = compound_order(head);
-			unsigned int pteshift;
-
-			local_irq_save(flags); /* disables as well */
-			pte = find_linux_pte(mm->pgd, cur_ua, NULL, &pteshift);
-
-			/* Double check it is still the same pinned page */
-			if (pte && pte_page(*pte) == head &&
-			    pteshift == compshift + PAGE_SHIFT)
-				pageshift = max_t(unsigned int, pteshift,
-						PAGE_SHIFT);
-			local_irq_restore(flags);
+
+			pageshift = compound_order(head) + PAGE_SHIFT;
 		}
 		mem->pageshift = min(mem->pageshift, pageshift);
 		/*