On Mon, 6 May 2019 16:58:03 -0400
Eric Farman wrote:
> On 5/6/19 1:17 PM, Cornelia Huck wrote:
> > If a ccw has CCW_FLAG_SKIP set, and the command is of type
> > read, read backwards, or sense, no data should be written
> > to the guest for that command.
> >
> > Signed-off-by: Cornelia Huck
> > ---
> >
> > Only extremely lightly tested (i.e., can boot a guest.)
> >
> > ---
> > hw/s390x/css.c | 22 ++
> > include/hw/s390x/css.h | 1 +
> > 2 files changed, 19 insertions(+), 4 deletions(-)
> >
> > diff --git a/hw/s390x/css.c b/hw/s390x/css.c
> > index 8fc9e35ba5d3..6ee31cc2e08f 100644
> > --- a/hw/s390x/css.c
> > +++ b/hw/s390x/css.c
> > @@ -830,8 +830,12 @@ static int ccw_dstream_rw_noflags(CcwDataStream *cds,
> > void *buff, int len,
> > if (op == CDS_OP_A) {
> > goto incr;
> > }
> > -ret = address_space_rw(_space_memory, cds->cda,
> > - MEMTXATTRS_UNSPECIFIED, buff, len, op);
> > +if (!cds->do_skip) {
> > +ret = address_space_rw(_space_memory, cds->cda,
> > + MEMTXATTRS_UNSPECIFIED, buff, len, op);
> > +} else {
> > +ret = 0;
> > +}
> > if (ret != MEMTX_OK) {
> > cds->flags |= CDS_F_STREAM_BROKEN;
> > return -EINVAL;
> > @@ -928,8 +932,13 @@ static int ccw_dstream_rw_ida(CcwDataStream *cds, void
> > *buff, int len,
> > do {
> > iter_len = MIN(len, cont_left);
> > if (op != CDS_OP_A) {
> > -ret = address_space_rw(_space_memory, cds->cda,
> > - MEMTXATTRS_UNSPECIFIED, buff, iter_len,
> > op);
> > +if (!cds->do_skip) {
> > +ret = address_space_rw(_space_memory, cds->cda,
> > + MEMTXATTRS_UNSPECIFIED, buff,
> > iter_len,
> > + op);
> > +} else {
> > +ret = 0;
> > +}
> > if (ret != MEMTX_OK) {
> > /* assume inaccessible address */
> > ret = -EINVAL; /* channel program check */
> > @@ -968,6 +977,11 @@ void ccw_dstream_init(CcwDataStream *cds, CCW1 const
> > *ccw, ORB const *orb)
> >
> > cds->count = ccw->count;
> > cds->cda_orig = ccw->cda;
> > +/* skip is only effective for read, read backwards, or sense commands
> > */
> > +cds->do_skip = (ccw->flags & CCW_FLAG_SKIP) &&
> > +(ccw->cmd_code & CCW_CMD_BASIC_SENSE ||
> > + ccw->cmd_code & 0x02 /* read */ ||
> > + ccw->cmd_code & 0x0c /* read backwards */);
>
> I wish so badly that these checks work, since it'd simplify the vfio-ccw
> code, but I don't think this lets you tell the difference between a READ
> (x02) and a NOP (x03) or any other control-type CCW. Ditto
> read-backward versus TIC. :-(
Drat, why is that never easy... I'll rework this check.
>
> > ccw_dstream_rewind(cds);
> > if (!(cds->flags & CDS_F_IDA)) {
> > cds->op_handler = ccw_dstream_rw_noflags;
> > diff --git a/include/hw/s390x/css.h b/include/hw/s390x/css.h
> > index aae19c427229..7cc183ef4366 100644
> > --- a/include/hw/s390x/css.h
> > +++ b/include/hw/s390x/css.h
> > @@ -97,6 +97,7 @@ typedef struct CcwDataStream {
> > int (*op_handler)(struct CcwDataStream *cds, void *buff, int len,
> > CcwDataStreamOp op);
> > hwaddr cda;
> > +bool do_skip;
> > } CcwDataStream;
> >
> > /*
> >
>
