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authorPaolo Bonzini <pbonzini@redhat.com>2015-09-16 17:26:16 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2015-09-25 12:04:41 +0200
commit0eb2baeb449d27d6e6208a257dba6be1aad4d476 (patch)
treeb5a99cbff011e402822b636fbf054c772bf4d591 /hw
parent5e43efb29ae877da131e6c1a4761cd7f4eec5a16 (diff)
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scsi-generic: let guests recognize readonly=on on passthrough devices
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. Reviewed-by: Fam Zheng <famz@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'hw')
-rw-r--r--hw/scsi/scsi-generic.c14
1 files changed, 14 insertions, 0 deletions
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);
}