[Qemu-devel] [PATCH 1/7] virtio_get_byteswap: function for endian-ambivalent targets using virtio.

[Rusty Russell <rusty@rustcorp.com.au>]

virtio data structures are defined as "target endian", which assumes
that's a fixed value.  In fact, that actually means it's
platform-specific.

The OASIS virtio 1.0 spec will fix this.  Meanwhile, create a hook for
little endian ppc (and potentially ARM).  This is called at device
reset time (which is done before any driver is loaded) since it
may involve a system call to get the status when running under kvm.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 hw/virtio/virtio.c                |   6 ++
 include/hw/virtio/virtio-access.h | 133 ++++++++++++++++++++++++++++++++++++++
 include/hw/virtio/virtio.h        |   2 +
 stubs/Makefile.objs               |   1 +
 stubs/virtio_get_byteswap.c       |   6 ++
 5 files changed, 148 insertions(+)
 create mode 100644 include/hw/virtio/virtio-access.h
 create mode 100644 stubs/virtio_get_byteswap.c

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 2f1e73b..7730780 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -18,6 +18,9 @@
 #include "hw/virtio/virtio.h"
 #include "qemu/atomic.h"
 #include "hw/virtio/virtio-bus.h"
+#include "hw/virtio/virtio-access.h"
+
+bool virtio_byteswap = false;
 
 /*
  * The alignment to use between consumer and producer parts of vring.
@@ -543,6 +546,9 @@ void virtio_reset(void *opaque)
 
     virtio_set_status(vdev, 0);
 
+    /* We assume all devices are the same endian. */
+    virtio_byteswap = virtio_get_byteswap();
+
     if (k->reset) {
         k->reset(vdev);
     }
diff --git a/include/hw/virtio/virtio-access.h b/include/hw/virtio/virtio-access.h
new file mode 100644
index 0000000..2263c9c
--- /dev/null
+++ b/include/hw/virtio/virtio-access.h
@@ -0,0 +1,133 @@
+/*
+ * Virtio Accessor Support: In case your target can change endian.
+ *
+ * Copyright IBM, Corp. 2013
+ *
+ * Authors:
+ *  Rusty Russell   <rusty@au.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+#ifndef _QEMU_VIRTIO_ACCESS_H
+#define _QEMU_VIRTIO_ACCESS_H
+#include "hw/virtio/virtio.h"
+
+/* Initialized by virtio_get_byteswap() at any virtio device reset. */
+extern bool virtio_byteswap;
+
+static inline uint16_t virtio_lduw_phys(hwaddr pa)
+{
+    if (virtio_byteswap) {
+        return bswap16(lduw_phys(pa));
+    }
+    return lduw_phys(pa);
+    
+}
+
+static inline uint32_t virtio_ldl_phys(hwaddr pa)
+{
+    if (virtio_byteswap) {
+        return bswap32(ldl_phys(pa));
+    }
+    return ldl_phys(pa);
+}
+
+static inline uint64_t virtio_ldq_phys(hwaddr pa)
+{
+    if (virtio_byteswap) {
+        return bswap64(ldq_phys(pa));
+    }
+    return ldq_phys(pa);
+}
+
+static inline void virtio_stw_phys(hwaddr pa, uint16_t value)
+{
+    if (virtio_byteswap) {
+        stw_phys(pa, bswap16(value));
+    } else {
+        stw_phys(pa, value);
+    }
+}
+
+static inline void virtio_stl_phys(hwaddr pa, uint32_t value)
+{
+    if (virtio_byteswap) {
+        stl_phys(pa, bswap32(value));
+    } else {
+        stl_phys(pa, value);
+    }
+}
+
+static inline void virtio_stw_p(void *ptr, uint16_t v)
+{
+    if (virtio_byteswap) {
+        stw_p(ptr, bswap16(v));
+    } else {
+        stw_p(ptr, v);
+    }
+}
+
+static inline void virtio_stl_p(void *ptr, uint32_t v)
+{
+    if (virtio_byteswap) {
+        stl_p(ptr, bswap32(v));
+    } else {
+        stl_p(ptr, v);
+    }
+}
+
+static inline void virtio_stq_p(void *ptr, uint64_t v)
+{
+    if (virtio_byteswap) {
+        stq_p(ptr, bswap64(v));
+    } else {
+        stq_p(ptr, v);
+    }
+}
+
+static inline int virtio_lduw_p(const void *ptr)
+{
+    if (virtio_byteswap) {
+        return bswap16(lduw_p(ptr));
+    } else {
+        return lduw_p(ptr);
+    }
+}
+
+static inline int virtio_ldl_p(const void *ptr)
+{
+    if (virtio_byteswap) {
+        return bswap32(ldl_p(ptr));
+    } else {
+        return ldl_p(ptr);
+    }
+}
+
+static inline uint64_t virtio_ldq_p(const void *ptr)
+{
+    if (virtio_byteswap) {
+        return bswap64(ldq_p(ptr));
+    } else {
+        return ldq_p(ptr);
+    }
+}
+
+static inline uint32_t virtio_tswap32(uint32_t s)
+{
+    if (virtio_byteswap) {
+        return bswap32(tswap32(s));
+    } else {
+        return tswap32(s);
+    }
+}
+
+static inline void virtio_tswap32s(uint32_t *s)
+{
+    tswap32s(s);
+    if (virtio_byteswap) {
+        *s = bswap32(*s);
+    }
+}
+#endif /* _QEMU_VIRTIO_ACCESS_H */
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index a90522d..065e1d9 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -249,4 +249,6 @@ void virtio_queue_set_host_notifier_fd_handler(VirtQueue *vq, bool assign,
                                                bool set_handler);
 void virtio_queue_notify_vq(VirtQueue *vq);
 void virtio_irq(VirtQueue *vq);
+
+extern bool virtio_get_byteswap(void);
 #endif
diff --git a/stubs/Makefile.objs b/stubs/Makefile.objs
index df92fe5..7e7a9c8 100644
--- a/stubs/Makefile.objs
+++ b/stubs/Makefile.objs
@@ -27,3 +27,4 @@ stub-obj-y += vm-stop.o
 stub-obj-y += vmstate.o
 stub-obj-$(CONFIG_WIN32) += fd-register.o
 stub-obj-y += cpus.o
+stub-obj-y += virtio_get_byteswap.o
diff --git a/stubs/virtio_get_byteswap.c b/stubs/virtio_get_byteswap.c
new file mode 100644
index 0000000..7cf764d
--- /dev/null
+++ b/stubs/virtio_get_byteswap.c
@@ -0,0 +1,6 @@
+#include "hw/virtio/virtio.h"
+
+bool virtio_get_byteswap(void)
+{
+    return false;
+}
-- 
1.8.1.2