target/alpha: Switch to do_transaction_failed() hook

Switch the alpha target from the old unassigned_access hook
to the new do_transaction_failed hook. This allows us to
resolve a ??? in the old hook implementation.

The only part of the alpha target that does physical
memory accesses is reading the page table -- add a
TODO comment there to the effect that we should handle
bus faults on page table walks. (Since the palcode
doesn't actually do anything useful on a bus fault anyway
it's a bit moot for now.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <1502196172-13818-1-git-send-email-peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

target/alpha/cpu.c

@@ -297,7 +297,7 @@ static void alpha_cpu_class_init(ObjectClass *oc, void *data)
 #ifdef CONFIG_USER_ONLY
     cc->handle_mmu_fault = alpha_cpu_handle_mmu_fault;
 #else
-    cc->do_unassigned_access = alpha_cpu_unassigned_access;
+    cc->do_transaction_failed = alpha_cpu_do_transaction_failed;
     cc->do_unaligned_access = alpha_cpu_do_unaligned_access;
     cc->get_phys_page_debug = alpha_cpu_get_phys_page_debug;
     dc->vmsd = &vmstate_alpha_cpu;

target/alpha/cpu.h

@@ -486,9 +486,11 @@ void cpu_alpha_store_fpcr (CPUAlphaState *env, uint64_t val);
 uint64_t cpu_alpha_load_gr(CPUAlphaState *env, unsigned reg);
 void cpu_alpha_store_gr(CPUAlphaState *env, unsigned reg, uint64_t val);
 #ifndef CONFIG_USER_ONLY
-QEMU_NORETURN void alpha_cpu_unassigned_access(CPUState *cpu, hwaddr addr,
-                                               bool is_write, bool is_exec,
-                                               int unused, unsigned size);
+void alpha_cpu_do_transaction_failed(CPUState *cs, hwaddr physaddr,
+                                     vaddr addr, unsigned size,
+                                     MMUAccessType access_type,
+                                     int mmu_idx, MemTxAttrs attrs,
+                                     MemTxResult response, uintptr_t retaddr);
 #endif
 
 static inline void cpu_get_tb_cpu_state(CPUAlphaState *env, target_ulong *pc,

target/alpha/helper.c

@@ -163,6 +163,14 @@ static int get_physical_address(CPUAlphaState *env, target_ulong addr,
 
     pt = env->ptbr;
 
+    /* TODO: rather than using ldq_phys() to read the page table we should
+     * use address_space_ldq() so that we can handle the case when
+     * the page table read gives a bus fault, rather than ignoring it.
+     * For the existing code the zero data that ldq_phys will return for
+     * an access to invalid memory will result in our treating the page
+     * table as invalid, which may even be the right behaviour.
+     */
+
     /* L1 page table read.  */
     index = (addr >> (TARGET_PAGE_BITS + 20)) & 0x3ff;
     L1pte = ldq_phys(cs->as, pt + index*8);

target/alpha/mem_helper.c

@@ -49,22 +49,23 @@ void alpha_cpu_do_unaligned_access(CPUState *cs, vaddr addr,
     cpu_loop_exit(cs);
 }
 
-void alpha_cpu_unassigned_access(CPUState *cs, hwaddr addr,
-                                 bool is_write, bool is_exec, int unused,
-                                 unsigned size)
+void alpha_cpu_do_transaction_failed(CPUState *cs, hwaddr physaddr,
+                                     vaddr addr, unsigned size,
+                                     MMUAccessType access_type,
+                                     int mmu_idx, MemTxAttrs attrs,
+                                     MemTxResult response, uintptr_t retaddr)
 {
     AlphaCPU *cpu = ALPHA_CPU(cs);
     CPUAlphaState *env = &cpu->env;
 
+    if (retaddr) {
+        cpu_restore_state(cs, retaddr);
+    }
+
     env->trap_arg0 = addr;
-    env->trap_arg1 = is_write ? 1 : 0;
+    env->trap_arg1 = access_type == MMU_DATA_STORE ? 1 : 0;
     cs->exception_index = EXCP_MCHK;
     env->error_code = 0;
-
-    /* ??? We should cpu_restore_state to the faulting insn, but this hook
-       does not have access to the retaddr value from the original helper.
-       It's all moot until the QEMU PALcode grows an MCHK handler.  */
-
     cpu_loop_exit(cs);
 }