hw/pci-host/astro: Implement Hard Fail and Soft Fail mode

The Astro/Elroy chip can work in either Hard-Fail or Soft-Fail mode.

Hard fail means the system bus will send an HPMC (=crash) to the
processor, soft fail means the system bus will ignore timeouts of
MMIO-reads or MMIO-writes and return -1ULL.

The HF mode is controlled by a bit in the status register and is usually
programmed by the OS. Return the corresponing values based on the current
value of that bit.

Signed-off-by: Helge Deller <deller@gmx.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

hw/pci-host/astro.c

@@ -131,15 +131,21 @@ static MemTxResult elroy_chip_read_with_attrs(void *opaque, hwaddr addr,
             if (s->iosapic_reg_select < ARRAY_SIZE(s->iosapic_reg)) {
                 val = s->iosapic_reg[s->iosapic_reg_select];
             } else {
-                val = 0;
-                ret = MEMTX_DECODE_ERROR;
+                goto check_hf;
             }
         }
         trace_iosapic_reg_read(s->iosapic_reg_select, size, val);
         break;
     default:
-        val = 0;
-        ret = MEMTX_DECODE_ERROR;
+    check_hf:
+        if (s->status_control & HF_ENABLE) {
+            val = 0;
+            ret = MEMTX_DECODE_ERROR;
+        } else {
+            /* return -1ULL if HardFail is disabled */
+            val = ~0;
+            ret = MEMTX_OK;
+        }
     }
     trace_elroy_read(addr, size, val);
 
@@ -187,7 +193,7 @@ static MemTxResult elroy_chip_write_with_attrs(void *opaque, hwaddr addr,
         if (s->iosapic_reg_select < ARRAY_SIZE(s->iosapic_reg)) {
             s->iosapic_reg[s->iosapic_reg_select] = val;
         } else {
-            return MEMTX_DECODE_ERROR;
+            goto check_hf;
         }
         break;
     case 0x0840:                /* IOSAPIC_REG_EOI */
@@ -200,7 +206,10 @@ static MemTxResult elroy_chip_write_with_attrs(void *opaque, hwaddr addr,
         }
         break;
     default:
-        return MEMTX_DECODE_ERROR;
+    check_hf:
+        if (s->status_control & HF_ENABLE) {
+            return MEMTX_DECODE_ERROR;
+        }
     }
     return MEMTX_OK;
 }

include/hw/pci-host/astro.h

@@ -27,6 +27,8 @@ OBJECT_DECLARE_SIMPLE_TYPE(ElroyState, ELROY_PCI_HOST_BRIDGE)
 #define IOS_DIST_BASE_ADDR      0xfffee00000ULL
 #define IOS_DIST_BASE_SIZE           0x10000ULL
 
+#define HF_ENABLE       0x40    /* enable HF mode (default is -1 mode) */
+
 struct AstroState;
 
 struct ElroyState {