Patchwork [10/33] target-alpha: Cleanup MMU modes.

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Submitter Richard Henderson
Date April 28, 2011, 8:50 p.m.
Message ID <1304023875-25040-11-git-send-email-rth@twiddle.net>
Download mbox | patch
Permalink /patch/93307/
State New
Headers show

Comments

Richard Henderson - April 28, 2011, 8:50 p.m.
Don't bother including executive and supervisor modes.

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 target-alpha/cpu.h |   36 ++++++++++++++++++++++++++++--------
 1 files changed, 28 insertions(+), 8 deletions(-)

Patch

diff --git a/target-alpha/cpu.h b/target-alpha/cpu.h
index 1fc21dc..bdd396c 100644
--- a/target-alpha/cpu.h
+++ b/target-alpha/cpu.h
@@ -192,6 +192,33 @@  enum {
 
 #define SWCR_MASK  (SWCR_TRAP_ENABLE_MASK | SWCR_MAP_MASK | SWCR_STATUS_MASK)
 
+/* MMU modes definitions */
+
+/* Alpha has 5 MMU modes: PALcode, kernel, executive, supervisor, and user.
+   The Unix PALcode only exposes the kernel and user modes; presumably
+   executive and supervisor are used by VMS.
+
+   PALcode itself uses physical mode for code and kernel mode for data;
+   there are PALmode instructions that can access data via physical mode
+   or via an os-installed "alternate mode", which is one of the 4 above.
+
+   QEMU does not currently properly distinguish between code/data when
+   looking up addresses.  To avoid having to address this issue, our
+   emulated PALcode will cheat and use the KSEG mapping for its code+data
+   rather than physical addresses.
+
+   Moreover, we're only emulating Unix PALcode, and not attempting VMS.
+
+   All of which allows us to drop all but kernel and user modes.
+   Elide the unused MMU modes to save space.  */
+
+#define NB_MMU_MODES 2
+
+#define MMU_MODE0_SUFFIX _kernel
+#define MMU_MODE1_SUFFIX _user
+#define MMU_KERNEL_IDX   0
+#define MMU_USER_IDX     1
+
 typedef struct CPUAlphaState CPUAlphaState;
 
 struct CPUAlphaState {
@@ -246,16 +273,9 @@  struct CPUAlphaState {
 #define cpu_gen_code cpu_alpha_gen_code
 #define cpu_signal_handler cpu_alpha_signal_handler
 
-/* MMU modes definitions */
-#define NB_MMU_MODES 4
-#define MMU_MODE0_SUFFIX _kernel
-#define MMU_MODE1_SUFFIX _executive
-#define MMU_MODE2_SUFFIX _supervisor
-#define MMU_MODE3_SUFFIX _user
-#define MMU_USER_IDX 3
 static inline int cpu_mmu_index (CPUState *env)
 {
-    return (env->ps >> 3) & 3;
+    return (env->ps >> 3) & 1;
 }
 
 #include "cpu-all.h"