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>

1 files changed, 8 insertions, 0 deletions

diff --git a/target/alpha/helper.c b/target/alpha/helper.c
index 34121f4cad..36407f77f5 100644
--- a/target/alpha/helper.c
+++ b/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);