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From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To: tglx@linutronix.de,
	mingo@redhat.com,
	bp@alien8.de,
	dave.hansen@intel.com
Cc: sathyanarayanan.kuppuswamy@linux.intel.com,
	hpa@zytor.com,
	seanjc@google.com,
	elena.reshetova@intel.com,
	rick.p.edgecombe@intel.com,
	x86@kernel.org,
	linux-kernel@vger.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Chris Oo <cho@microsoft.com>,
	Dexuan Cui <decui@microsoft.com>
Subject: [PATCH] x86/tdx: Preserve shared bit on mprotect()
Date: Fri, 12 Apr 2024 22:12:47 +0300
Message-ID: <20240412191247.369841-1-kirill.shutemov@linux.intel.com>
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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'.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Fixes: 41394e33f3a0 ("x86/tdx: Extend the confidential computing API to support TDX guests")
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Chris Oo <cho@microsoft.com>
Cc: Dexuan Cui <decui@microsoft.com>
---
 arch/x86/include/asm/pgtable_types.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 3f648ffdfbe5..7dd2fdfacff3 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)
-- 
2.43.0