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Re: [Qemu-devel] [PATCH 2/3] hw/s390x/css: Remove QEMU_PACKED from struc
From: |
David Hildenbrand |
Subject: |
Re: [Qemu-devel] [PATCH 2/3] hw/s390x/css: Remove QEMU_PACKED from struct SenseId |
Date: |
Tue, 25 Sep 2018 18:52:28 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 |
On 25/09/2018 17:20, Thomas Huth 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().
>
> Signed-off-by: Thomas Huth <address@hidden>
> ---
> 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;
> }
> }
>
> @@ -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];
>
> - 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 {
>
Dumb idea: as migration under spark never worked, add some #idef
alignment fix for sparc only?
--
Thanks,
David / dhildenb