Index: sys/riscv/riscv/machdep.c
===================================================================
--- sys/riscv/riscv/machdep.c
+++ sys/riscv/riscv/machdep.c
@@ -84,6 +84,7 @@
 #include <machine/machdep.h>
 #include <machine/metadata.h>
 #include <machine/pcb.h>
+#include <machine/pte.h>
 #include <machine/reg.h>
 #include <machine/riscvreg.h>
 #include <machine/sbi.h>
@@ -826,6 +827,26 @@
 	if (fdt_get_mem_regions(mem_regions, &mem_regions_sz, NULL) != 0)
 		panic("Cannot get physical memory regions");
 	physmem_hardware_regions(mem_regions, mem_regions_sz);
+
+	/*
+	 * Exclude reserved memory specified by the device tree. Typically,
+	 * this contains an entry for memory used by the runtime SBI firmware.
+	 */
+	if (fdt_get_reserved_mem(mem_regions, &mem_regions_sz) == 0)
+		physmem_exclude_regions(mem_regions, mem_regions_sz,
+		    EXFLAG_NODUMP | EXFLAG_NOALLOC);
+	else
+		/*
+		 * XXX: Exclude the lowest 2MB of physical memory, since it is
+		 * assumed to contain the SBI firmware. This is a little
+		 * fragile, but it is consistent with the platforms we support
+		 * so far.
+		 *
+		 * TODO: remove this when the all regular booting methods
+		 * properly report reserved memory regions.
+		 */
+		physmem_exclude_region(mem_regions[0].mr_start, L2_SIZE,
+		    EXFLAG_NODUMP | EXFLAG_NOALLOC);
 #endif
 
 	/* Do basic tuning, hz etc */