[PATCH V3] target/riscv: Bugfix reserved bits in PTE for RV64

[guoren]

From: Guo Ren <address@hidden>

Highest 10 bits of PTE are reserved in riscv-privileged, ref: [1], so we
need to ignore them. They can not be a part of ppn.

1: The RISC-V Instruction Set Manual, Volume II: Privileged Architecture
   4.4 Sv39: Page-Based 39-bit Virtual-Memory System
   4.5 Sv48: Page-Based 48-bit Virtual-Memory System

Signed-off-by: Guo Ren <address@hidden>
Reviewed-by: Liu Zhiwei <address@hidden>
---
 target/riscv/cpu_bits.h   | 3 +++
 target/riscv/cpu_helper.c | 4 +++-
 2 files changed, 6 insertions(+), 1 deletion(-)
---
Changelog V3:
 - Use UUL define for PTE_RESERVED.
 - Keep ppn >> PTE_PPN_SHIFT 

Changelog V2:
 - Bugfix pte destroyed cause boot fail
 - Change to AND with a mask instead of shifting both directions

diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h
index e998348..cdc62a8 100644
--- a/target/riscv/cpu_bits.h
+++ b/target/riscv/cpu_bits.h
@@ -470,6 +470,9 @@
 #define PTE_D               0x080 /* Dirty */
 #define PTE_SOFT            0x300 /* Reserved for Software */
 
+/* Reserved highest 10 bits in PTE */
+#define PTE_RESERVED        0xFFC0000000000000ULL
+
 /* Page table PPN shift amount */
 #define PTE_PPN_SHIFT       10
 
diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index 87dd6a6..7e04ff5 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -258,10 +258,12 @@ restart:
         }
 #if defined(TARGET_RISCV32)
         target_ulong pte = ldl_phys(cs->as, pte_addr);
+        hwaddr ppn = pte;
 #elif defined(TARGET_RISCV64)
         target_ulong pte = ldq_phys(cs->as, pte_addr);
+        hwaddr ppn = pte & ~PTE_RESERVED;
 #endif
-        hwaddr ppn = pte >> PTE_PPN_SHIFT;
+        ppn = ppn >> PTE_PPN_SHIFT;
 
         if (!(pte & PTE_V)) {
             /* Invalid PTE */
-- 
2.7.4