Difftest: add xtval to snapshot

include/isa/riscv64.h

@@ -33,6 +33,7 @@ typedef struct {
   
   uint64_t satp, mip, mie, mscratch, sscratch, mideleg, medeleg;
 
+  uint64_t mtval, stval;
   uint64_t mode;
 
   bool amo;

src/isa/riscv64/difftest/difftest.h

 #ifndef __RISCV64_DIFF_TEST_H__
 #define __RISCV64_DIFF_TEST_H__
 
-#define DIFFTEST_REG_SIZE (sizeof(uint64_t) * (32 + 32 + 1 + 6 + 7 + 1))
+#define DIFFTEST_REG_SIZE (sizeof(uint64_t) * (32 + 32 + 1 + 6 + 9 + 1))
 // GRPs + FPRs + pc + [m|s][status|cause|epc] + other necessary CSRs + mode
 
 void isa_difftest_getregs_hook(void);

src/isa/riscv64/difftest/ref.c

@@ -22,6 +22,8 @@ static void csr_prepare() {
   cpu.sscratch = sscratch->val;
   cpu.mideleg  = mideleg->val;
   cpu.medeleg  = medeleg->val;
+  cpu.mtval    = mtval->val;
+  cpu.stval    = stval->val;
 }
 
 static void csr_writeback() {
@@ -40,6 +42,8 @@ static void csr_writeback() {
   sscratch->val = cpu.sscratch;
   mideleg->val  = cpu.mideleg;
   medeleg->val  = cpu.medeleg;
+  mtval->val    = cpu.mtval;
+  stval->val    = cpu.stval;
 }
 
 void isa_difftest_getregs(void *r) {