[PATCH] riscv: Raise an exception if pte reserved bits are not cleared

[Alexandre Ghiti]

As per the specification, in 64-bit, if any of the pte reserved bits 60-54
is set, an exception should be triggered (see 4.4.1, "Addressing and Memory
Protection"), so implement this behaviour in the address translation process.

Reported-by: Andrea Parri <andrea@rivosinc.com>
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
---
 target/riscv/cpu_bits.h   | 1 +
 target/riscv/cpu_helper.c | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h
index fca7ef0cef..8d9ba2ce11 100644
--- a/target/riscv/cpu_bits.h
+++ b/target/riscv/cpu_bits.h
@@ -640,6 +640,7 @@ typedef enum {
 #define PTE_SOFT            0x300 /* Reserved for Software */
 #define PTE_PBMT            0x6000000000000000ULL /* Page-based memory types */
 #define PTE_N               0x8000000000000000ULL /* NAPOT translation */
+#define PTE_RESERVED        0x1FC0000000000000ULL /* Reserved bits */
 #define PTE_ATTR            (PTE_N | PTE_PBMT) /* All attributes bits */
 
 /* Page table PPN shift amount */
diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index f88c503cf4..39c323a865 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -936,6 +936,11 @@ restart:
             return TRANSLATE_FAIL;
         }
 
+        /* PTE reserved bits must be cleared otherwise an exception is raised 
*/
+        if (riscv_cpu_mxl(env) == MXL_RV64 && (pte & PTE_RESERVED)) {
+            return TRANSLATE_FAIL;
+        }
+
         bool pbmte = env->menvcfg & MENVCFG_PBMTE;
         bool hade = env->menvcfg & MENVCFG_HADE;
 
-- 
2.37.2