linux-kernel - [PATCHv2 05/14] mm/khugepaged: Do not collapse pages in encrypted VMAs

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Date:   Wed, 28 Mar 2018 19:55:31 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Tom Lendacky <thomas.lendacky@....com>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCHv2 05/14] mm/khugepaged: Do not collapse pages in encrypted VMAs

Pages for encrypted VMAs have to be allocated in a special way:
we would need to propagate down not only desired NUMA node but also
whether the page is encrypted.

It complicates not-so-trivial routine of huge page allocation in
khugepaged even more. It also puts more pressure on page allocator:
we cannot re-use pages allocated for encrypted VMA to collapse
page in unencrypted one or vice versa.

I think for now it worth skipping encrypted VMAs. We can return
to this topic later.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 include/linux/mm.h | 7 +++++++
 mm/khugepaged.c    | 2 ++
 2 files changed, 9 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6c50f77c75d5..b6a72eb82f4b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1479,6 +1479,13 @@ static inline bool vma_is_anonymous(struct vm_area_struct *vma)
 	return !vma->vm_ops;
 }
 
+#ifndef vma_is_encrypted
+static inline bool vma_is_encrypted(struct vm_area_struct *vma)
+{
+	return false;
+}
+#endif
+
 #ifndef vma_keyid
 static inline int vma_keyid(struct vm_area_struct *vma)
 {
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index e42568284e06..42f33fd526a0 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -835,6 +835,8 @@ static bool hugepage_vma_check(struct vm_area_struct *vma)
 		return false;
 	if (is_vma_temporary_stack(vma))
 		return false;
+	if (vma_is_encrypted(vma))
+		return false;
 	return !(vma->vm_flags & VM_NO_KHUGEPAGED);
 }
 
-- 
2.16.2