From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35408) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZcEeZ-0002tD-US for qemu-devel@nongnu.org; Wed, 16 Sep 2015 11:29:48 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZcEeU-00077f-2r for qemu-devel@nongnu.org; Wed, 16 Sep 2015 11:29:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38832) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZcEeT-00077S-Uj for qemu-devel@nongnu.org; Wed, 16 Sep 2015 11:29:42 -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 AF350461C1 for ; Wed, 16 Sep 2015 15:29:41 +0000 (UTC) From: Paolo Bonzini Date: Wed, 16 Sep 2015 17:29:39 +0200 Message-Id: <1442417379-5626-1-git-send-email-pbonzini@redhat.com> Subject: [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: qemu-devel@nongnu.org Cc: famz@redhat.com 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