linux-kernel - [tip: x86/urgent] x86/tdx: Preserve shared bit on mprotect()

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Date: Wed, 24 Apr 2024 17:37:52 -0000
From: "tip-bot2 for Kirill A. Shutemov" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Chris Oo <cho@...rosoft.com>,
 "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
 Dave Hansen <dave.hansen@...ux.intel.com>,
 Rick Edgecombe <rick.p.edgecombe@...el.com>,
 Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>,
 Tom Lendacky <thomas.lendacky@....com>, stable@...r.kernel.org,
 x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/urgent] x86/tdx: Preserve shared bit on mprotect()

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     a0a8d15a798be4b8f20aca2ba91bf6b688c6a640
Gitweb:        https://git.kernel.org/tip/a0a8d15a798be4b8f20aca2ba91bf6b688c6a640
Author:        Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
AuthorDate:    Wed, 24 Apr 2024 11:20:35 +03:00
Committer:     Dave Hansen <dave.hansen@...ux.intel.com>
CommitterDate: Wed, 24 Apr 2024 08:11:43 -07:00

x86/tdx: Preserve shared bit on mprotect()

The TDX guest platform takes one bit from the physical address to
indicate if the page is shared (accessible by VMM). This bit is not part
of the physical_mask and is not preserved during mprotect(). As a
result, the 'shared' bit is lost during mprotect() on shared mappings.

_COMMON_PAGE_CHG_MASK specifies which PTE bits need to be preserved
during modification. AMD includes 'sme_me_mask' in the define to
preserve the 'encrypt' bit.

To cover both Intel and AMD cases, include 'cc_mask' in
_COMMON_PAGE_CHG_MASK instead of 'sme_me_mask'.

Reported-and-tested-by: Chris Oo <cho@...rosoft.com>

Fixes: 41394e33f3a0 ("x86/tdx: Extend the confidential computing API to support TDX guests")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/all/20240424082035.4092071-1-kirill.shutemov%40linux.intel.com
---
 arch/x86/include/asm/coco.h          | 1 +
 arch/x86/include/asm/pgtable_types.h | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/coco.h b/arch/x86/include/asm/coco.h
index c086699..aa6c8f8 100644
--- a/arch/x86/include/asm/coco.h
+++ b/arch/x86/include/asm/coco.h
@@ -25,6 +25,7 @@ u64 cc_mkdec(u64 val);
 void cc_random_init(void);
 #else
 #define cc_vendor (CC_VENDOR_NONE)
+static const u64 cc_mask = 0;

 static inline u64 cc_mkenc(u64 val)
 {
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 0b748ee..9abb8cc 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -148,7 +148,7 @@
 #define _COMMON_PAGE_CHG_MASK	(PTE_PFN_MASK | _PAGE_PCD | _PAGE_PWT |	\
 				 _PAGE_SPECIAL | _PAGE_ACCESSED |	\
 				 _PAGE_DIRTY_BITS | _PAGE_SOFT_DIRTY |	\
-				 _PAGE_DEVMAP | _PAGE_ENC | _PAGE_UFFD_WP)
+				 _PAGE_DEVMAP | _PAGE_CC | _PAGE_UFFD_WP)
 #define _PAGE_CHG_MASK	(_COMMON_PAGE_CHG_MASK | _PAGE_PAT)
 #define _HPAGE_CHG_MASK (_COMMON_PAGE_CHG_MASK | _PAGE_PSE | _PAGE_PAT_LARGE)

@@ -173,6 +173,7 @@ enum page_cache_mode {
 };
 #endif

+#define _PAGE_CC		(_AT(pteval_t, cc_mask))
 #define _PAGE_ENC		(_AT(pteval_t, sme_me_mask))

 #define _PAGE_CACHE_MASK	(_PAGE_PWT | _PAGE_PCD | _PAGE_PAT)