arch-riscv: Increase maximum stack size

This patch increases the maximum stack size of RISC-V, which should help
to reduce problems with programs that allocate large amounts of data on
the stack or do many small allocations.

Change-Id: I1d760050229b12f01a4a8f24c047b587299fef6d
Reviewed-on: https://gem5-review.googlesource.com/6661
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Alec Roelke <ar4jc@virginia.edu>

src/arch/riscv/process.cc

@@ -61,7 +61,7 @@ RiscvProcess::RiscvProcess(ProcessParams * params,
     ObjectFile *objFile) : Process(params, objFile)
 {
     const Addr stack_base = 0x7FFFFFFFFFFFFFFFL;
-    const Addr max_stack_size = PageBytes * 64;
+    const Addr max_stack_size = 8 * 1024 * 1024;
     const Addr next_thread_stack_base = stack_base - max_stack_size;
     const Addr brk_point = roundUp(objFile->bssBase() + objFile->bssSize(),
             PageBytes);