On Tue, 25 Sep 2018 17:20:08 +0200 Thomas Huth <th...@redhat.com> wrote:
> The uint16_t member cu_type of struct SenseId is not naturally aligned, > and since the struct is marked with QEMU_PACKED, this can lead to > unaligned memory accesses - which does not work on architectures like > Sparc. Thus remove the QEMU_PACKED here and rather copy the struct > byte by byte when we do copy_sense_id_to_guest(). Hm... would it look nicer if we chopped up {cu,dev}_type into a hi/lo byte and keep the QEMU_PACKED? (The ciws should be ok, I think.) > > Signed-off-by: Thomas Huth <th...@redhat.com> > --- > hw/s390x/css.c | 35 +++++++++++++++++++---------------- > include/hw/s390x/css.h | 2 +- > 2 files changed, 20 insertions(+), 17 deletions(-) > > diff --git a/hw/s390x/css.c b/hw/s390x/css.c > index 5a9fe45..aaa2efa 100644 > --- a/hw/s390x/css.c > +++ b/hw/s390x/css.c > @@ -750,20 +750,23 @@ static void sch_handle_halt_func(SubchDev *sch) > > } > > -static void copy_sense_id_to_guest(SenseId *dest, SenseId *src) > +static void copy_sense_id_to_guest(uint8_t *dest, SenseId *src) > { > int i; > > - dest->reserved = src->reserved; > - dest->cu_type = cpu_to_be16(src->cu_type); > - dest->cu_model = src->cu_model; > - dest->dev_type = cpu_to_be16(src->dev_type); > - dest->dev_model = src->dev_model; > - dest->unused = src->unused; > - for (i = 0; i < ARRAY_SIZE(dest->ciw); i++) { > - dest->ciw[i].type = src->ciw[i].type; > - dest->ciw[i].command = src->ciw[i].command; > - dest->ciw[i].count = cpu_to_be16(src->ciw[i].count); > + dest[0] = src->reserved; > + dest[1] = src->cu_type >> 8; > + dest[2] = src->cu_type & 0xff; > + dest[3] = src->cu_model; > + dest[4] = src->dev_type >> 8; > + dest[5] = src->dev_type & 0xff; > + dest[6] = src->dev_model; > + dest[7] = src->unused; > + for (i = 0; i < ARRAY_SIZE(src->ciw); i++) { > + dest[8 + i * 4] = src->ciw[i].type; > + dest[9 + i * 4] = src->ciw[i].command; > + dest[10 + i * 4] = src->ciw[i].count >> 8; > + dest[11 + i * 4] = src->ciw[i].count & 0xff; /me gets a headache while trying to understand the endianness here... > } > } > > @@ -1044,9 +1047,9 @@ static int css_interpret_ccw(SubchDev *sch, hwaddr > ccw_addr, > break; > case CCW_CMD_SENSE_ID: > { > - SenseId sense_id; > + uint8_t sense_id[256]; If we go with this approach, maybe add a #define here? The documentation ("Common I/O Device Commands") defines the sense id data to be at most 256 bytes, so that would fit nicely. > > - copy_sense_id_to_guest(&sense_id, &sch->id); > + copy_sense_id_to_guest(sense_id, &sch->id); > /* Sense ID information is device specific. */ > if (check_len) { > if (ccw.count != sizeof(sense_id)) { > @@ -1060,11 +1063,11 @@ static int css_interpret_ccw(SubchDev *sch, hwaddr > ccw_addr, > * have enough place to store at least bytes 0-3. > */ > if (len >= 4) { > - sense_id.reserved = 0xff; > + sense_id[0] = 0xff; > } else { > - sense_id.reserved = 0; > + sense_id[0] = 0; > } > - ccw_dstream_write_buf(&sch->cds, &sense_id, len); > + ccw_dstream_write_buf(&sch->cds, sense_id, len); > sch->curr_status.scsw.count = ccw_dstream_residual_count(&sch->cds); > ret = 0; > break; > diff --git a/include/hw/s390x/css.h b/include/hw/s390x/css.h > index 9da5912..bec82d0 100644 > --- a/include/hw/s390x/css.h > +++ b/include/hw/s390x/css.h > @@ -48,7 +48,7 @@ typedef struct SenseId { > uint8_t unused; /* padding byte */ > /* extended part */ > CIW ciw[MAX_CIWS]; /* variable # of CIWs */ > -} QEMU_PACKED SenseId; > +} SenseId; /* Note: No QEMU_PACKED due to unaligned > members */ > > /* Channel measurements, from linux/drivers/s390/cio/cmf.c. */ > typedef struct CMB {