[libvirt] [PATCH] qemu: raise an error when trying to use readonly ide disks

[Martin Kletzander]

On Mon, Jun 30, 2014 at 12:05:06PM +0200, Giuseppe Scrivano wrote:
>The IDE bus doesn't support readonly disks, so inform the user with an
>error message instead of let qemu fail with a more obscure "Device
>'ide-hd' could not be initialized" error message.
>
>Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1112939
>
>Signed-off-by: Giuseppe Scrivano <gscrivan at redhat.com>
>---
> src/qemu/qemu_command.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
>diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
>index 63f322a..4829176 100644
>--- a/src/qemu/qemu_command.c
>+++ b/src/qemu/qemu_command.c
>@@ -3385,8 +3385,15 @@ qemuBuildDriveStr(virConnectPtr conn,
>         disk->bus != VIR_DOMAIN_DISK_BUS_IDE)
>         virBufferAddLit(&opt, ",boot=on");
>     if (disk->readonly &&
>-        virQEMUCapsGet(qemuCaps, QEMU_CAPS_DRIVE_READONLY))
>+        virQEMUCapsGet(qemuCaps, QEMU_CAPS_DRIVE_READONLY)) {
>+        if (disk->bus == VIR_DOMAIN_DISK_BUS_IDE &&
>+            disk->device == VIR_DOMAIN_DISK_DEVICE_DISK) {
>+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
>+                           _("readonly ide disks are not supported"));
>+            goto error;
>+        }
>         virBufferAddLit(&opt, ",readonly=on");
>+    }

I'm not very sure we should do that.  Second opinion would be great.
My point is that if qemu does not support the readonly flag, we just
skip setting it, but if it supports it, we will error out?  OTOH
skipping the readonly=on when user requests it is, ehm, not nice
either.  I think Eric was saying that *some* readonly flags do not
make much of a sense, but that was probably WRT backing chains or
something like that.  Eric?

Martin

>     if (disk->transient) {
>         virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
>                        _("transient disks not supported yet"));
>--
>1.9.3
>
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