linux-kernel - [RFC, PATCH 14/22] mm, khugepaged: Do not collapse pages in encrypted VMAs

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Date:   Mon,  5 Mar 2018 19:26:02 +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: [RFC, PATCH 14/22] 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. I 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>
---
 mm/khugepaged.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index b7e2268dfc9a..601151678414 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -830,6 +830,8 @@ 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);
 }

-- 
2.16.1