[Qemu-devel] [PATCH for-1.6] mips_malta: do not raise exceptions when accessing invalid memory

[Aurelien Jarno]

Since commit c658b94f6e8c206c59d02aa6fbac285b86b53d2c, MIPS raises
exceptions when accessing invalid memory. This is not the correct
behaviour for MIPS Malta Core LV, as the GT-64120A system controller
just ignore undecoded access. This feature is used by the Linux kernel
to probe for some devices.

Emulate the correct behaviour in QEMU by adding an empty slot covering
the entire memory space decoded by the GT-64120A.

Signed-off-by: Aurelien Jarno <address@hidden>
---
 default-configs/mips-softmmu.mak     |    1 +
 default-configs/mips64-softmmu.mak   |    1 +
 default-configs/mips64el-softmmu.mak |    1 +
 default-configs/mipsel-softmmu.mak   |    1 +
 hw/mips/mips_malta.c                 |    6 ++++++
 5 files changed, 10 insertions(+)

diff --git a/default-configs/mips-softmmu.mak b/default-configs/mips-softmmu.mak
index 926709a..71177ef 100644
--- a/default-configs/mips-softmmu.mak
+++ b/default-configs/mips-softmmu.mak
@@ -34,3 +34,4 @@ CONFIG_JAZZ_LED=y
 CONFIG_MC146818RTC=y
 CONFIG_VT82C686=y
 CONFIG_ISA_TESTDEV=y
+CONFIG_EMPTY_SLOT=y
diff --git a/default-configs/mips64-softmmu.mak 
b/default-configs/mips64-softmmu.mak
index 0ef3f09..617301b 100644
--- a/default-configs/mips64-softmmu.mak
+++ b/default-configs/mips64-softmmu.mak
@@ -34,3 +34,4 @@ CONFIG_JAZZ_LED=y
 CONFIG_MC146818RTC=y
 CONFIG_VT82C686=y
 CONFIG_ISA_TESTDEV=y
+CONFIG_EMPTY_SLOT=y
diff --git a/default-configs/mips64el-softmmu.mak 
b/default-configs/mips64el-softmmu.mak
index 6089318..317b151 100644
--- a/default-configs/mips64el-softmmu.mak
+++ b/default-configs/mips64el-softmmu.mak
@@ -36,3 +36,4 @@ CONFIG_JAZZ_LED=y
 CONFIG_MC146818RTC=y
 CONFIG_VT82C686=y
 CONFIG_ISA_TESTDEV=y
+CONFIG_EMPTY_SLOT=y
diff --git a/default-configs/mipsel-softmmu.mak 
b/default-configs/mipsel-softmmu.mak
index cd59e24..532a9ae 100644
--- a/default-configs/mipsel-softmmu.mak
+++ b/default-configs/mipsel-softmmu.mak
@@ -34,3 +34,4 @@ CONFIG_JAZZ_LED=y
 CONFIG_MC146818RTC=y
 CONFIG_VT82C686=y
 CONFIG_ISA_TESTDEV=y
+CONFIG_EMPTY_SLOT=y
diff --git a/hw/mips/mips_malta.c b/hw/mips/mips_malta.c
index 0f5de33..61cb3e4 100644
--- a/hw/mips/mips_malta.c
+++ b/hw/mips/mips_malta.c
@@ -50,6 +50,7 @@
 #include "qemu/host-utils.h"
 #include "sysemu/qtest.h"
 #include "qemu/error-report.h"
+#include "hw/empty_slot.h"
 
 //#define DEBUG_BOARD_INIT
 
@@ -908,6 +909,11 @@ void mips_malta_init(QEMUMachineInitArgs *args)
     DeviceState *dev = qdev_create(NULL, TYPE_MIPS_MALTA);
     MaltaState *s = MIPS_MALTA(dev);
 
+    /* The whole address space decoded by the GT-64120A doesn't generate
+       exception when accessing invalid memory. Create an empty slot to
+       emulate this feature. */
+    empty_slot_init(0, 0x1fffffff);
+
     qdev_init_nofail(dev);
 
     /* Make sure the first 3 serial ports are associated with a device. */
-- 
1.7.10.4