Raise store/AMO access fault on CBO to shadow-stack page

Proliferating the access_flags isn't ideal, but it wasn't clear how
better to handle this case.

riscv/mmu.cc

@@ -553,8 +553,8 @@ reg_t mmu_t::walk(mem_access_info_t access_info)
       // not shadow stack access xwr=110 or xwr=010 page cause page fault
       // shadow stack access with PTE_X moved to following check
       break;
-    } else if (ss_page && (type == STORE && !ss_access)) {
-      // not shadow stack store and  xwr = 010 cause access-fault
+    } else if (ss_page && ((type == STORE && !ss_access) || access_info.flags.clean_inval)) {
+      // non-shadow-stack store or CBO with xwr = 010 causes access-fault
       throw trap_store_access_fault(virt, addr, 0, 0);
     } else if (ss_page && type == FETCH) {
       // fetch from shadow stack pages cause instruction access-fault

riscv/mmu.h

@@ -43,9 +43,10 @@ struct xlate_flags_t {
   const bool hlvx : 1 {false};
   const bool lr : 1 {false};
   const bool ss_access : 1 {false};
+  const bool clean_inval : 1 {false};
 
   bool is_special_access() const {
-    return forced_virt || hlvx || lr || ss_access;
+    return forced_virt || hlvx || lr || ss_access || clean_inval;
   }
 };
 
@@ -232,14 +233,14 @@ class mmu_t
   }
 
   void clean_inval(reg_t addr, bool clean, bool inval) {
-    auto access_info = generate_access_info(addr, LOAD, {});
+    auto access_info = generate_access_info(addr, LOAD, {.clean_inval = true});
     reg_t transformed_addr = access_info.transformed_vaddr;
 
     auto base = transformed_addr & ~(blocksz - 1);
     for (size_t offset = 0; offset < blocksz; offset += 1)
       check_triggers(triggers::OPERATION_STORE, base + offset, false, transformed_addr, std::nullopt);
     convert_load_traps_to_store_traps({
-      const reg_t paddr = translate(generate_access_info(transformed_addr, LOAD, {}), 1);
+      const reg_t paddr = translate(access_info, 1);
       if (sim->reservable(paddr)) {
         if (tracer.interested_in_range(paddr, paddr + PGSIZE, LOAD))
           tracer.clean_invalidate(paddr, blocksz, clean, inval);