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Date: Wed, 25 Jan 2012 17:47:19 +1100
Message-ID: <CAN05THRiO5S-TkD9rcA93ZmrVjwPCmAU2TRkfePkoOA1y+PcLg@mail.gmail.com>
From: ronnie sahlberg <ronniesahlberg@gmail.com>
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Subject: Re: [Qemu-devel] [PATCH] iSCSI: add configuration variables for
	iSCSI
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To: Eric Blake <eblake@redhat.com>
Cc: kwolf@redhat.com, qemu-devel@nongnu.org

On Tue, Jan 24, 2012 at 5:07 AM, Eric Blake <eblake@redhat.com> wrote:
>
> Can -readconfig support reading from an inherited fd, rather than only
> taking a file name that qemu has to open()?
>
...
>
> Can you give an actual command line that uses -readconfig, as part of
> your example?
>

Thanks for the review Eric.
I will update the patch with an example using -readconfig and fix the typo.


Yes,  -readconfig can read from a pipe()  and it can also read from an
arbitrary file descriptor.

Reading from a pipe :
cat iscsi.conf | ./x86_64-softmmu/qemu-system-x86_64 -enable-kvm
-display vnc=127.0.0.1:0 -drive
file=iscsi://127.0.0.1/iqn.ronnie.test/1 -readconfig /proc/self/fd/0

Read from an arbitrary filedescriptor inherited from the parent process :
9<iscsi.conf ./x86_64-softmmu/qemu-system-x86_64 -enable-kvm -display
vnc=127.0.0.1:0 -drive file=iscsi://127.0.0.1/iqn.ronnie.test/1
-readconfig /proc/self/fd/9


The second example shows how you can have qemu read from an arbitrary
descriptor that is inherited from the parent process (the shell in
this case)
I imagine you would pipe() then fork() and pass the read side of your
pipe to qemu here ?


If this works well or at least in some acceptable form it might be
useful for other users needing to pass sensitive config data into QEMU
too?


regards
ronnie sahlberg