From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55277) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZcR85-0008Uy-UM for qemu-devel@nongnu.org; Thu, 17 Sep 2015 00:49:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZcR81-0007TO-Ua for qemu-devel@nongnu.org; Thu, 17 Sep 2015 00:49:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53326) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZcR81-0007Sz-Pe for qemu-devel@nongnu.org; Thu, 17 Sep 2015 00:49:01 -0400 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (Postfix) with ESMTPS id 5D903C0B2008 for ; Thu, 17 Sep 2015 04:49:00 +0000 (UTC) Date: Thu, 17 Sep 2015 12:48:56 +0800 From: Fam Zheng Message-ID: <20150917044856.GA11527@ad.nay.redhat.com> References: <1442417379-5626-1-git-send-email-pbonzini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1442417379-5626-1-git-send-email-pbonzini@redhat.com> Subject: Re: [Qemu-devel] [PATCH] scsi-generic: let guests recognize readonly=on on passthrough devices List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: qemu-devel@nongnu.org On Wed, 09/16 17:29, Paolo Bonzini wrote: > Passed-through SCSI devices can be opened with the readonly=on option. > When this happens, Linux filters away write commands so that the guest > cannot overwrite the contents of the device. > > However, the guest does not know that the device is read-only, and > accepts writes. The writes only fail later when the page cache is > flushed. > > This patch modifies scsi-generic to modify the MODE SENSE data and > set the read-only bit in the device-specific parameters, so that > the guest OS treats the disk as write protected. > > Signed-off-by: Paolo Bonzini > --- > hw/scsi/scsi-generic.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c > index 1b6350b..a4626f7 100644 > --- a/hw/scsi/scsi-generic.c > +++ b/hw/scsi/scsi-generic.c > @@ -210,6 +210,20 @@ static void scsi_read_complete(void * opaque, int ret) > } > blk_set_guest_block_size(s->conf.blk, s->blocksize); > > + /* Patch MODE SENSE device specific parameters if the BDS is opened > + * readonly. > + */ > + if ((s->type == TYPE_DISK || s->type == TYPE_TAPE) && > + blk_is_read_only(s->conf.blk) && > + (r->req.cmd.buf[0] == MODE_SENSE || > + r->req.cmd.buf[0] == MODE_SENSE_10) && > + (r->req.cmd.buf[1] & 0x8) == 0) { > + if (r->req.cmd.buf[0] == MODE_SENSE) { > + r->buf[2] |= 0x80; > + } else { > + r->buf[3] |= 0x80; > + } > + } > scsi_req_data(&r->req, len); > scsi_req_unref(&r->req); > } > -- > 2.5.0 > > Reviewed-by: Fam Zheng