[kvm-unit-tests PATCH v3 13/17] x86 AMD SEV: Page table with c-bit

[Zixuan Wang <zxwang42@xxxxxxxxx>]

From: Zixuan Wang <zixuanwang@xxxxxxxxxx>

AMD SEV introduces c-bit to page table entries. To work with AMD SEV:

   1. c-bit should be set for new page table entries
   2. address calculation should not use c-bit as part of address

Signed-off-by: Zixuan Wang <zixuanwang@xxxxxxxxxx>
---
 lib/x86/amd_sev.c  | 10 ++++++++++
 lib/x86/amd_sev.h  |  1 +
 lib/x86/asm/page.h | 27 ++++++++++++++++++++++++---
 lib/x86/vm.c       | 18 ++++++++++++++----
 4 files changed, 49 insertions(+), 7 deletions(-)

diff --git a/lib/x86/amd_sev.c b/lib/x86/amd_sev.c
index 13e6455..b555355 100644
--- a/lib/x86/amd_sev.c
+++ b/lib/x86/amd_sev.c
@@ -73,3 +73,13 @@ unsigned long long get_amd_sev_c_bit_mask(void)
 		return 0;
 	}
 }
+
+unsigned long long get_amd_sev_addr_upperbound(void)
+{
+	if (amd_sev_enabled()) {
+		return amd_sev_c_bit_pos - 1;
+	} else {
+		/* Default memory upper bound */
+		return PT_ADDR_UPPER_BOUND_DEFAULT;
+	}
+}
diff --git a/lib/x86/amd_sev.h b/lib/x86/amd_sev.h
index 68483c9..7de12f0 100644
--- a/lib/x86/amd_sev.h
+++ b/lib/x86/amd_sev.h
@@ -39,6 +39,7 @@ bool amd_sev_enabled(void);
 efi_status_t setup_amd_sev(void);
 
 unsigned long long get_amd_sev_c_bit_mask(void);
+unsigned long long get_amd_sev_addr_upperbound(void);
 
 #endif /* TARGET_EFI */
 
diff --git a/lib/x86/asm/page.h b/lib/x86/asm/page.h
index f6f740b..c25bc66 100644
--- a/lib/x86/asm/page.h
+++ b/lib/x86/asm/page.h
@@ -25,6 +25,12 @@ typedef unsigned long pgd_t;
 #define LARGE_PAGE_SIZE	(1024 * PAGE_SIZE)
 #endif
 
+#ifdef TARGET_EFI
+/* lib/x86/amd_sev.c */
+extern unsigned long long get_amd_sev_c_bit_mask(void);
+extern unsigned long long get_amd_sev_addr_upperbound(void);
+#endif /* TARGET_EFI */
+
 #define PT_PRESENT_MASK		(1ull << 0)
 #define PT_WRITABLE_MASK	(1ull << 1)
 #define PT_USER_MASK		(1ull << 2)
@@ -33,10 +39,25 @@ typedef unsigned long pgd_t;
 #define PT_PAGE_SIZE_MASK	(1ull << 7)
 #define PT_GLOBAL_MASK		(1ull << 8)
 #define PT64_NX_MASK		(1ull << 63)
-#define PT_ADDR_MASK		GENMASK_ULL(51, 12)
 
-#define PDPTE64_PAGE_SIZE_MASK	  (1ull << 7)
-#define PDPTE64_RSVD_MASK	  GENMASK_ULL(51, cpuid_maxphyaddr())
+/*
+ * Without AMD SEV, the default address upper bound is 51 (i.e., pte bit 51 and
+ * lower bits are addresses). But with AMD SEV enabled, the upper bound is one
+ * bit lower than the c-bit position.
+ */
+#define PT_ADDR_UPPER_BOUND_DEFAULT	(51)
+
+#ifdef TARGET_EFI
+#define PT_ADDR_UPPER_BOUND	(get_amd_sev_addr_upperbound())
+#else
+#define PT_ADDR_UPPER_BOUND	(PT_ADDR_UPPER_BOUND_DEFAULT)
+#endif /* TARGET_EFI */
+
+#define PT_ADDR_LOWER_BOUND	(PAGE_SHIFT)
+#define PT_ADDR_MASK		GENMASK_ULL(PT_ADDR_UPPER_BOUND, PT_ADDR_LOWER_BOUND)
+
+#define PDPTE64_PAGE_SIZE_MASK	(1ull << 7)
+#define PDPTE64_RSVD_MASK	GENMASK_ULL(PT_ADDR_UPPER_BOUND, cpuid_maxphyaddr())
 
 #define PT_AD_MASK              (PT_ACCESSED_MASK | PT_DIRTY_MASK)
 
diff --git a/lib/x86/vm.c b/lib/x86/vm.c
index 5cd2ee4..0ebc860 100644
--- a/lib/x86/vm.c
+++ b/lib/x86/vm.c
@@ -26,6 +26,9 @@ pteval_t *install_pte(pgd_t *cr3,
                 pt_page = 0;
 	    memset(new_pt, 0, PAGE_SIZE);
 	    pt[offset] = virt_to_phys(new_pt) | PT_PRESENT_MASK | PT_WRITABLE_MASK | pte_opt_mask;
+#ifdef TARGET_EFI
+	    pt[offset] |= get_amd_sev_c_bit_mask();
+#endif /* TARGET_EFI */
 	}
 	pt = phys_to_virt(pt[offset] & PT_ADDR_MASK);
     }
@@ -63,7 +66,7 @@ struct pte_search find_pte_level(pgd_t *cr3, void *virt,
 		if (r.level == lowest_level)
 			return r;
 
-		pt = phys_to_virt(pte & 0xffffffffff000ull);
+		pt = phys_to_virt(pte & PT_ADDR_MASK);
 	}
 }
 
@@ -94,13 +97,20 @@ pteval_t *get_pte_level(pgd_t *cr3, void *virt, int pte_level)
 
 pteval_t *install_large_page(pgd_t *cr3, phys_addr_t phys, void *virt)
 {
-    return install_pte(cr3, 2, virt,
-		       phys | PT_PRESENT_MASK | PT_WRITABLE_MASK | pte_opt_mask | PT_PAGE_SIZE_MASK, 0);
+    phys_addr_t flags = PT_PRESENT_MASK | PT_WRITABLE_MASK | pte_opt_mask | PT_PAGE_SIZE_MASK;
+#ifdef TARGET_EFI
+    flags |= get_amd_sev_c_bit_mask();
+#endif /* TARGET_EFI */
+    return install_pte(cr3, 2, virt, phys | flags, 0);
 }
 
 pteval_t *install_page(pgd_t *cr3, phys_addr_t phys, void *virt)
 {
-    return install_pte(cr3, 1, virt, phys | PT_PRESENT_MASK | PT_WRITABLE_MASK | pte_opt_mask, 0);
+    phys_addr_t flags = PT_PRESENT_MASK | PT_WRITABLE_MASK | pte_opt_mask;
+#ifdef TARGET_EFI
+    flags |= get_amd_sev_c_bit_mask();
+#endif /* TARGET_EFI */
+    return install_pte(cr3, 1, virt, phys | flags, 0);
 }
 
 void install_pages(pgd_t *cr3, phys_addr_t phys, size_t len, void *virt)
-- 
2.33.0