[Qemu-devel] [PATCH v1 1/1] hw/scsi: Report errors and sense to guests through scsi-block

[Alistair Francis <alistair.francis@wdc.com>]

From: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>

When host block devices are bridged to a guest system through
virtio-scsi-pci and scsi-block driver, scsi_handle_rw_error() in
hw/scsi/scsi-disk.c checks the error number to judge which error to
report to the guests. EIO and EINVAL are not reported and ignored. Once
EIO or EINVAL happen, eternal wait of guest system happens. This problem
was observed with zoned block devices on the host system attached to the
guest via virtio-scsi-pci. To avoid the eternal wait, add EIO and EINVAL
to the list of error numbers to report to the guest.

On top of this, it is required to report SCSI sense data to the guest
so that the guest can handle the error correctly. However,
scsi_handle_rw_error() does not passthrough sense data that host
scsi-block device reported. Instead, it newly generates fixed sense
data only for certain error numbers. This is inflexible to support new
error codes to report to guest. To avoid this inflexiblity, pass the SCSI
sense data that the host scsi-block device reported as is. To be more
precise, set valid sense_len in the SCSIDiskReq referring sb_len_wr that
host SCSI device SG_IO ioctl reported. Add update_sense callback to
SCSIDiskClass to refer the SG_IO ioctl result only when scsi-block device
is targeted.

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
---
 hw/scsi/scsi-disk.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index ed7295bfd7..6801e3a0d0 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -62,6 +62,7 @@ typedef struct SCSIDiskClass {
     DMAIOFunc       *dma_readv;
     DMAIOFunc       *dma_writev;
     bool            (*need_fua_emulation)(SCSICommand *cmd);
+    void            (*update_sense)(SCSIRequest *r);
 } SCSIDiskClass;
 
 typedef struct SCSIDiskReq {
@@ -438,6 +439,7 @@ static bool scsi_handle_rw_error(SCSIDiskReq *r, int error, bool acct_failed)
 {
     bool is_read = (r->req.cmd.mode == SCSI_XFER_FROM_DEV);
     SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
+    SCSIDiskClass *sdc = (SCSIDiskClass *) object_get_class(OBJECT(s));
     BlockErrorAction action = blk_get_error_action(s->qdev.conf.blk,
                                                    is_read, error);
 
@@ -452,9 +454,12 @@ static bool scsi_handle_rw_error(SCSIDiskReq *r, int error, bool acct_failed)
              * pause the host.
              */
             assert(r->status && *r->status);
+            if (sdc->update_sense) {
+                sdc->update_sense(&r->req);
+            }
             error = scsi_sense_buf_to_errno(r->req.sense, sizeof(r->req.sense));
             if (error == ECANCELED || error == EAGAIN || error == ENOTCONN ||
-                error == 0)  {
+                error == EIO || error == EINVAL || error == 0)  {
                 /* These errors are handled by guest. */
                 scsi_req_complete(&r->req, *r->status);
                 return true;
@@ -2894,6 +2899,13 @@ static int scsi_block_parse_cdb(SCSIDevice *d, SCSICommand *cmd,
     }
 }
 
+static void scsi_block_update_sense(SCSIRequest *req)
+{
+    SCSIDiskReq *r = DO_UPCAST(SCSIDiskReq, req, req);
+    SCSIBlockReq *br = DO_UPCAST(SCSIBlockReq, req, r);
+    r->req.sense_len = MIN(br->io_header.sb_len_wr, sizeof(r->req.sense));
+}
+
 #endif
 
 static
@@ -3059,6 +3071,7 @@ static void scsi_block_class_initfn(ObjectClass *klass, void *data)
     sc->parse_cdb    = scsi_block_parse_cdb;
     sdc->dma_readv   = scsi_block_dma_readv;
     sdc->dma_writev  = scsi_block_dma_writev;
+    sdc->update_sense = scsi_block_update_sense;
     sdc->need_fua_emulation = scsi_block_no_fua;
     dc->desc = "SCSI block device passthrough";
     dc->props = scsi_block_properties;
-- 
2.22.0