Skip storing in store_func if actually_store is false, add a fake store at start of AMO.

This includes skipping store in store_slow_path.

Is okay to skip the mmio_store part too, since the access_fault for mmio_failure will be caught on the actual store.

The ordering for the mmio_access fault is irrelevant since it will occur after the TW faults, and load faults are converted to store faults.

Will catch any faults from the access but won't perform a store.

Since store permissions can only be granted if read permissions exist,

any store faults will occur before or at the same time as a load fault.

Thus this store permissions check is sufficient for properly catching the faults in an Amo access TW.

1 files changed, 2 insertions, 0 deletions

diff --git a/riscv/mmu.cc b/riscv/mmu.cc
index 6c7af21..40dccf0 100644
--- a/riscv/mmu.cc
+++ b/riscv/mmu.cc
@@ -172,6 +172,7 @@ void mmu_t::store_slow_path(reg_t addr, reg_t len, const uint8_t* bytes, uint32_
       throw *matched_trigger;
   }
 
+  if (actually_store) {
   if (auto host_addr = sim->addr_to_mem(paddr)) {
     memcpy(host_addr, bytes, len);
     if (tracer.interested_in_range(paddr, paddr + PGSIZE, STORE))
@@ -181,6 +182,7 @@ void mmu_t::store_slow_path(reg_t addr, reg_t len, const uint8_t* bytes, uint32_
   } else if (!mmio_store(paddr, len, bytes)) {
     throw trap_store_access_fault((proc) ? proc->state.v : false, addr, 0, 0);
   }
+  }
 }
 
 tlb_entry_t mmu_t::refill_tlb(reg_t vaddr, reg_t paddr, char* host_addr, access_type type)