virtio-pci: Fix endianness of virtio config

The virtio config area in PIO space is a bit special. The initial
header is little endian but the rest (device specific) is guest
native endian.

The PIO accessors for PCI on machines that don't have native IO ports
assume that all PIO is little endian, which works fine for everything
except the above.

A complicated way to fix it would be to split the BAR into two memory
regions with different endianess settings, but this isn't practical
to do, besides, the PIO code doesn't honor region endianness anyway
(I have a patch for that too but it isn't necessary at this stage).

So I decided to go for the quick fix instead which consists of
reverting the swap in virtio-pci in selected places, hoping that when
we eventually do a "v2" of the virtio protocols, we sort that out once
and for all using a fixed endian setting for everything.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
[agraf: keep virtio in libhw and determine endianness through a
        helper function in exec.c]
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/exec.c b/exec.c
index 7f9f730250..5b9eb9aa19 100644
--- a/exec.c
+++ b/exec.c
@@ -4390,6 +4390,20 @@ tb_page_addr_t get_page_addr_code(CPUState *env1, target_ulong addr)
     return qemu_ram_addr_from_host_nofail(p);
 }
 
+/*
+ * A helper function for the _utterly broken_ virtio device model to find out if
+ * it's running on a big endian machine. Don't do this at home kids!
+ */
+bool virtio_is_big_endian(void);
+bool virtio_is_big_endian(void)
+{
+#if defined(TARGET_WORDS_BIGENDIAN)
+    return true;
+#else
+    return false;
+#endif
+}
+
 #define MMUSUFFIX _cmmu
 #undef GETPC
 #define GETPC() NULL