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Date: Tue, 07 Jan 2014 21:48:17 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] TRIM/DISCARD/UNMAP support on qemu-nbd
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To: "Richard W.M. Jones" <rjones@redhat.com>
Cc: Teng-Feng Yang <shinrairis@gmail.com>, qemu-devel@nongnu.org

Il 07/01/2014 21:27, Richard W.M. Jones ha scritto:
> Not much more what I said in the original email (especially see the
> attached script which you can download from the bottom of this page:
> https://lists.gnu.org/archive/html/qemu-devel/2014-01/msg00084.html )
> 
> Basically it tries to dd /dev/zero into the virtio-scsi device exposed
> by qemu, then calls sg_unmap (there are two devices, it only unmaps
> the first so we can hopefully see the difference), but it doesn't seem
> to have any effect on the underlying file.  The underlying file is a
> regular raw-format file on ext4.
> 
> I called sg_readcap/sg_vpd and we seem to have all the right
> capability bits exposed.
> 
> This script won't work with regular libguestfs.  I compiled a special
> appliance that had the sg tools included.

Try again with the pull request of
http://permalink.gmane.org/gmane.comp.emulators.qemu/248421

Paolo