[Qemu-devel] [v7 Patch 4/5]Qemu: Add commandline -drive option 'hostcache'

[Supriya Kannery <supriyak@linux.vnet.ibm.com>]

qemu command option 'hostcache' added to -drive for block devices.
While starting a VM from qemu commandline, this option can be used 
for setting host cache usage for block data access. Simultaneous
use of 'hostcache' and 'cache' options not allowed.

Signed-off-by: Supriya Kannery <supriyak@linux.vnet.ibm.com>

---
 blockdev.c      |   13 +++++++++++++
 qemu-config.c   |    4 ++++
 qemu-options.hx |    2 +-
 3 files changed, 18 insertions(+), 1 deletion(-)

Index: qemu/blockdev.c
===================================================================
--- qemu.orig/blockdev.c
+++ qemu/blockdev.c
@@ -237,6 +237,7 @@ DriveInfo *drive_init(QemuOpts *opts, in
     DriveInfo *dinfo;
     int snapshot = 0;
     int ret;
+    int hostcache = 0;
 
     translation = BIOS_ATA_TRANSLATION_AUTO;
     media = MEDIA_DISK;
@@ -319,7 +320,19 @@ DriveInfo *drive_init(QemuOpts *opts, in
 	}
     }
 
+    if ((hostcache = qemu_opt_get_bool(opts, "hostcache", -1)) != -1) {
+        if (!hostcache) {
+            bdrv_flags |= BDRV_O_NOCACHE;
+        } else {
+            bdrv_flags &= ~BDRV_O_NOCACHE;
+        }
+    }
+
     if ((buf = qemu_opt_get(opts, "cache")) != NULL) {
+        if (hostcache != -1) {
+            error_report("'hostcache' and 'cache' cannot co-exist");
+            return NULL;
+        }
         if (bdrv_parse_cache_flags(buf, &bdrv_flags) != 0) {
             error_report("invalid cache option");
             return NULL;
Index: qemu/qemu-options.hx
===================================================================
--- qemu.orig/qemu-options.hx
+++ qemu/qemu-options.hx
@@ -135,7 +135,7 @@ DEF("drive", HAS_ARG, QEMU_OPTION_drive,
     "       [,cyls=c,heads=h,secs=s[,trans=t]][,snapshot=on|off]\n"
     "       [,cache=writethrough|writeback|none|directsync|unsafe][,format=f]\n"
     "       [,serial=s][,addr=A][,id=name][,aio=threads|native]\n"
-    "       [,readonly=on|off]\n"
+    "       [,readonly=on|off][,hostcache=on|off]\n"
     "                use 'file' as a drive image\n", QEMU_ARCH_ALL)
 STEXI
 @item -drive @var{option}[,@var{option}[,@var{option}[,...]]]
Index: qemu/qemu-config.c
===================================================================
--- qemu.orig/qemu-config.c
+++ qemu/qemu-config.c
@@ -85,6 +85,10 @@ static QemuOptsList qemu_drive_opts = {
             .name = "readonly",
             .type = QEMU_OPT_BOOL,
             .help = "open drive file as read-only",
+        },{
+            .name = "hostcache",
+            .type = QEMU_OPT_BOOL,
+            .help = "set or reset hostcache (on/off)"
         },
         { /* end of list */ }
     },