kernel/amd64: bus: Move MMIO_OFFSET to bus.h

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/sys/include/arch/amd64/bus.h b/sys/include/arch/amd64/bus.h
index 8f9bc39..b9d3362 100644
--- a/sys/include/arch/amd64/bus.h
+++ b/sys/include/arch/amd64/bus.h
@@ -32,6 +32,14 @@
 
 #include <sys/types.h>
 
+/*
+ * Hyra assumes that the bootloader uses PDE[256] for some
+ * higher half mappings. To avoid conflicts with those mappings,
+ * this offset is used to start device memory at PDE[257]. This
+ * will give us more than enough space.
+ */
+#define MMIO_OFFSET (VM_HIGHER_HALF + 0x8000000000)
+
 typedef uint64_t bus_addr_t;
 
 int bus_map(bus_addr_t addr, size_t size, int flags, void **vap);