[Qemu-devel] [PATCH] Add an error_report when failing to open due to block-drv-whitelist

[Ryan Harper <ryanh@us.ibm.com>]

When configure qemu with --block-drv-whitelist we don't report when we are
blocked by the white list and the resulting error message is misleading:

./configure --target-list=x86_64-softmmu \
            --block-drv-whitelist=qcow2,raw,host_device,host_cdrom

x86_64-softmmu/qemu-system-x86_64 -L pc-bios -m 512 -drive \
        file=fedora9_32_20G.qcow2,if=ide -monitor stdio
qemu: could not open disk image fedora9_32_20G.qcow2: Inappropriate ioctl for device

Which might lead one to look at the bdrv probe functions for floppy/cdrom
because we indeed will get an ioctl failure stored in errno and we report this
in vl.c when we get a non-zero return value from bdrv_open().

This patch adds an error report when we fail the whitelist and changes the errno
value to ENOPROTOOPT which was the closest thing I could think of that matched
the actual error.

Now we get the following output on whitelist failure:

x86_64-softmmu/qemu-system-x86_64 -L pc-bios -m 512 -drive \
        file=fedora9_32_20G.qcow2,if=ide -monitor stdio
qemu-system-x86_64: -drive file=fedora9_32_20G.qcow2,if=ide: block-drv-whitelist prevents using format 'file'
qemu: could not open disk image fedora9_32_20G.qcow2: Protocol not supported

Signed-off-by: Ryan Harper <ryanh@us.ibm.com>
---
 block.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/block.c b/block.c
index 39724c1..ffcf7f2 100644
--- a/block.c
+++ b/block.c
@@ -403,6 +403,9 @@ static int bdrv_open_common(BlockDriverState *bs, const char *filename,
     pstrcpy(bs->filename, sizeof(bs->filename), filename);
 
     if (use_bdrv_whitelist && !bdrv_is_whitelisted(drv)) {
+        error_report("block-drv-whitelist prevents using format '%s'", drv->format_name);
+        /* reset errno since we're failing because of whitelist restrictions */
+        errno = EPROTONOSUPPORT;
         return -ENOTSUP;
     }
 
-- 
1.6.3.3



-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
ryanh@us.ibm.com