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@microsoft.com>
Fixes: 41394e33f3a0 ("x86/tdx: Extend the confidential computing API to support TDX guests")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20240424082035.4092071-1-kirill.shutemov%40linux.intel.com

diff --git a/arch/x86/include/asm/coco.h b/arch/x86/include/asm/coco.h
index c086699b0d0c59fc62834bb457963f1b81b541d3..aa6c8f8ca9588e90894750ce4f93226c05af9c23 100644 (file)
--- 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 0b748ee16b3d94ea09516ee14e187dbebae0bf4a..9abb8cc4cd4747f4982655d425df997852b1553b 100644 (file)
--- 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)