[Xen-changelog] [xen-unstable] Make QEMU consistently report write caching support for emulated IDE

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kfraser@xxxxxxxxxxxxxxxxxxxxx
# Date 1184147295 -3600
# Node ID 637ff26be6ff820d185d8cdc5cc344aea6b5c9e2
# Parent  ff51ff907f8cce9d10296507e6c4c666cf603876
Make QEMU consistently report write caching support for emulated IDE
drives to fix a hang during SLES 9 HVM guest installation.

Without this, the SLES 9 installer kernels (32 and 64 bit) were
getting inconsistent information from QEMU as to whether the
(emulated) IDE drives support write caching (which they do).  So part
of the kernel thought write caching was enabled (and enabled the usage
of barrier writes) and part of it didn't, which triggered a bug in
which the same barrier write is submitted over and over again ...

Fixed by setting another bit in the WIN_IDENTIFY (IDE drive "identify"
command) response to indicate we really, truly support write caching.

Signed-off-by: David Lively <dlively@xxxxxxxxxxxxxxx>
Signed-off-by: Ben Guthro <bguthro@xxxxxxxxxxxxxxx>
---
 tools/ioemu/hw/ide.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletion(-)

diff -r ff51ff907f8c -r 637ff26be6ff tools/ioemu/hw/ide.c
--- a/tools/ioemu/hw/ide.c      Tue Jul 10 23:42:13 2007 +0100
+++ b/tools/ioemu/hw/ide.c      Wed Jul 11 10:48:15 2007 +0100
@@ -596,7 +596,8 @@ static void ide_identify(IDEState *s)
     /* 13=flush_cache_ext,12=flush_cache,10=lba48 */
     put_le16(p + 83, (1 << 14) | (1 << 13) | (1 <<12) | (1 << 10));
     put_le16(p + 84, (1 << 14));
-    put_le16(p + 85, (1 << 14));
+    /* 14=nop 5=write_cache */
+    put_le16(p + 85, (1 << 14) | (1 << 5));
     /* 13=flush_cache_ext,12=flush_cache,10=lba48 */
     put_le16(p + 86, (1 << 14) | (1 << 13) | (1 <<12) | (1 << 10));
     put_le16(p + 87, (1 << 14));

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