linux-kernel - [RFC, PATCH 16/22] x86/mm: Preserve KeyID on pte_modify() and pgprot

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Message-Id: <20180305162610.37510-17-kirill.shutemov@linux.intel.com>
Date:   Mon,  5 Mar 2018 19:26:04 +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 16/22] x86/mm: Preserve KeyID on pte_modify() and pgprot_modify()

Encrypted VMA would have KeyID stored in vma->vm_page_prot. This way we
don't need to do anything special to setup encrypted page table entries
and don't need to reserve space for KeyID in a VMA.

This patch changes _PAGE_CHG_MASK to include KeyID bits. Otherwise they
are going to be stripped from vm_page_prot on the first pgprot_modify().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/include/asm/pgtable_types.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 246f15b4e64c..800f66770163 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -121,8 +121,13 @@
  * protection key is treated like _PAGE_RW, for
  * instance, and is *not* included in this mask since
  * pte_modify() does modify it.
+ *
+ * It includes full range of PFN bits regardless if they were claimed for KeyID
+ * or not: we want to preserve KeyID on pte_modify() and pgprot_modify().
  */
-#define _PAGE_CHG_MASK	(PTE_PFN_MASK | _PAGE_PCD | _PAGE_PWT |		\
+#define PTE_PFN_MASK_MAX \
+	(((signed long)PAGE_MASK) & ((1UL << __PHYSICAL_MASK_SHIFT) - 1))
+#define _PAGE_CHG_MASK	(PTE_PFN_MASK_MAX | _PAGE_PCD | _PAGE_PWT |		\
 			 _PAGE_SPECIAL | _PAGE_ACCESSED | _PAGE_DIRTY |	\
 			 _PAGE_SOFT_DIRTY)
 #define _HPAGE_CHG_MASK (_PAGE_CHG_MASK | _PAGE_PSE)
-- 
2.16.1