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Re: [Qemu-devel] Re: [PATCH] usb-msd: Add usb-storage, removable=on|off
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] Re: [PATCH] usb-msd: Add usb-storage, removable=on|off property |
Date: |
Mon, 17 Jan 2011 10:04:05 +0000 |
User-agent: |
Mutt/1.5.20 (2009-06-14) |
On Mon, Jan 17, 2011 at 10:21:26AM +0100, Christoph Hellwig wrote:
> The actual removable bit looks fine, but I don't think the connection of
> the change callback looks sane. What's the rationale for it?
Since we're using bdrv_set_removable(), the user may try to eject the
block device from the QEMU monitor. At that point we have a closed
BlockDriverState and all operations will (at best) error since there is
no medium.
The callback removes the USB MSD so that eject is equivalent to removing
the device. It's a hack and we could remove it, but then we're left
with a weird guest-visible state that you can't get into with a physical
USB thumbdrive.
I was considering not using bdrv_set_removable() and instead adding a
hint to the BlockDriverState which gets checked when constructing the
SCSI INQUIRY response. If we take that approach, then QEMU doesn't
consider the block device removable in the eject/change medium sense.
Stefan