[Xen-devel] [PATCH v3 4/6] xen/arm: traps: MMIO should only be emulated for fault translation

[Julien Grall <julien.grall@xxxxxxx>]

The function do_trap_data_abort_guest assumes that a stage-2 data abort
can only be taken for a translation fault or permission fault today.

Whilst this is true today, it might not be in the future. Rather than
emulating the MMIO for any fault other than the permission one, print
a warning message when the fault is not handled by Xen.

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

---
    Changes in v2:
        - Add Stefano's reviewed-by
---
 xen/arch/arm/traps.c | 51 ++++++++++++++++++++++++++++-----------------------
 1 file changed, 28 insertions(+), 23 deletions(-)

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 7206a7e..46922eb 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -2467,35 +2467,40 @@ static void do_trap_data_abort_guest(struct 
cpu_user_regs *regs,
         /* Trap was triggered by mem_access, work here is done */
         if ( !rc )
             return;
+        break;
     }
-    break;
-    }
-
-    if ( dabt.s1ptw )
-        goto bad_data_abort;
+    case FSC_FLT_TRANS:
+        if ( dabt.s1ptw )
+            goto bad_data_abort;
 
-    /* XXX: Decode the instruction if ISS is not valid */
-    if ( !dabt.valid )
-        goto bad_data_abort;
+        /* XXX: Decode the instruction if ISS is not valid */
+        if ( !dabt.valid )
+            goto bad_data_abort;
 
-    /*
-     * Erratum 766422: Thumb store translation fault to Hypervisor may
-     * not have correct HSR Rt value.
-     */
-    if ( check_workaround_766422() && (regs->cpsr & PSR_THUMB) && dabt.write )
-    {
-        rc = decode_instruction(regs, &info.dabt);
-        if ( rc )
+        /*
+         * Erratum 766422: Thumb store translation fault to Hypervisor may
+         * not have correct HSR Rt value.
+         */
+        if ( check_workaround_766422() && (regs->cpsr & PSR_THUMB) &&
+             dabt.write )
         {
-            gprintk(XENLOG_DEBUG, "Unable to decode instruction\n");
-            goto bad_data_abort;
+            rc = decode_instruction(regs, &info.dabt);
+            if ( rc )
+            {
+                gprintk(XENLOG_DEBUG, "Unable to decode instruction\n");
+                goto bad_data_abort;
+            }
         }
-    }
 
-    if (handle_mmio(&info))
-    {
-        advance_pc(regs, hsr);
-        return;
+        if ( handle_mmio(&info) )
+        {
+            advance_pc(regs, hsr);
+            return;
+        }
+        break;
+    default:
+        gprintk(XENLOG_WARNING, "Unsupported DFSC: HSR=%#x DFSC=%#x\n",
+                hsr.bits, dabt.dfsc);
     }
 
 bad_data_abort:
-- 
1.9.1


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