On Fri, 15 Nov 2019 04:34:34 +0100
Eric Farman <far...@linux.ibm.com> wrote:
> From: Farhan Ali <al...@linux.ibm.com>
>
> The schib region can be used to obtain the latest SCHIB from the host
> passthrough subchannel. Since the guest SCHIB is virtualized,
> we currently only update the path related information so that the
> guest is aware of any path related changes when it issues the
> 'stsch' instruction.
One important information here is that you tweak the generic stsch
handling, although the behaviour remains the same for non-vfio
subchannels.
>
> Signed-off-by: Farhan Ali <al...@linux.ibm.com>
> Signed-off-by: Eric Farman <far...@linux.ibm.com>
> ---
>
> Notes:
> v0->v1: [EF]
> - Change various incarnations of "update chp status" to
> "handle_store", to reflect the STSCH instruction that will
> drive this code
> - Remove temporary variable for casting/testing purposes in
> s390_ccw_store(), and add a block comment of WHY its there.
> - Add a few comments to vfio_ccw_handle_store()
>
> hw/s390x/css.c | 8 ++++--
> hw/s390x/s390-ccw.c | 20 +++++++++++++
> hw/vfio/ccw.c | 57 +++++++++++++++++++++++++++++++++++++
> include/hw/s390x/css.h | 3 +-
> include/hw/s390x/s390-ccw.h | 1 +
> target/s390x/ioinst.c | 3 +-
> 6 files changed, 87 insertions(+), 5 deletions(-)
>
> diff --git a/hw/s390x/css.c b/hw/s390x/css.c
> index 844caab408..6ee6a96d75 100644
> --- a/hw/s390x/css.c
> +++ b/hw/s390x/css.c
> @@ -1335,11 +1335,15 @@ static void copy_schib_to_guest(SCHIB *dest, const
> SCHIB *src)
> }
> }
>
> -int css_do_stsch(SubchDev *sch, SCHIB *schib)
> +IOInstEnding css_do_stsch(SubchDev *sch, SCHIB *schib)
> {
> + int ret = IOINST_CC_EXPECTED;
It's a bit useless initializing ret here, given that you use it right
below :)
> +
Maybe add a comment here:
/*
* For some subchannels, we may want to update parts of
* the schib (e.g. update path masks from the host device
* for passthrough subchannels).
*/
> + ret = s390_ccw_store(sch);
> +
> /* Use current status. */
> copy_schib_to_guest(schib, &sch->curr_status);
> - return 0;
> + return ret;
> }
>
> static void copy_pmcw_from_guest(PMCW *dest, const PMCW *src)
> diff --git a/hw/s390x/s390-ccw.c b/hw/s390x/s390-ccw.c
> index 0c5a5b60bd..be0b379338 100644
> --- a/hw/s390x/s390-ccw.c
> +++ b/hw/s390x/s390-ccw.c
> @@ -51,6 +51,26 @@ int s390_ccw_clear(SubchDev *sch)
> return cdc->handle_clear(sch);
> }
>
> +IOInstEnding s390_ccw_store(SubchDev *sch)
> +{
> + S390CCWDeviceClass *cdc = NULL;
> + int ret = IOINST_CC_EXPECTED;
> +
> + /*
> + * This only applies to passthrough devices, so we can't unconditionally
> + * set this variable like we would for halt/clear.
Hm, can we maybe handle this differently? We have a generic ccw_cb in
the subchannel structure for ccw interpretation; would it make sense to
add a generic callback for stsch there as well?
(This works fine, though. Might want to add the check for halt/clear as
well, but that might be a bit overkill.)
> + */
> + if (object_dynamic_cast(OBJECT(sch->driver_data), TYPE_S390_CCW)) {
> + cdc = S390_CCW_DEVICE_GET_CLASS(sch->driver_data);
> + }
> +
> + if (cdc && cdc->handle_store) {
> + ret = cdc->handle_store(sch);
> + }
> +
> + return ret;
> +}
> +
> static void s390_ccw_get_dev_info(S390CCWDevice *cdev,
> char *sysfsdev,
> Error **errp)
> diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
> index 3e32bc1819..2ff223470f 100644
> --- a/hw/vfio/ccw.c
> +++ b/hw/vfio/ccw.c
> @@ -41,6 +41,9 @@ struct VFIOCCWDevice {
> uint64_t async_cmd_region_size;
> uint64_t async_cmd_region_offset;
> struct ccw_cmd_region *async_cmd_region;
> + uint64_t schib_region_size;
> + uint64_t schib_region_offset;
> + struct ccw_schib_region *schib_region;
> EventNotifier io_notifier;
> bool force_orb_pfch;
> bool warned_orb_pfch;
> @@ -124,6 +127,45 @@ again:
> }
> }
>
> +static IOInstEnding vfio_ccw_handle_store(SubchDev *sch)
> +{
> + S390CCWDevice *cdev = sch->driver_data;
> + VFIOCCWDevice *vcdev = DO_UPCAST(VFIOCCWDevice, cdev, cdev);
> + SCHIB *schib = &sch->curr_status;
> + struct ccw_schib_region *region = vcdev->schib_region;
> + SCHIB *s = (SCHIB *)region->schib_area;
You probably don't want to access region until after you checked it's
not NULL :)
> + int ret;
> +
> + /* schib region not available so nothing else to do */
> + if (!region) {
> + return IOINST_CC_EXPECTED;
> + }
> +
> + memset(region, 0, sizeof(*region));
> + ret = pread(vcdev->vdev.fd, region, vcdev->schib_region_size,
> + vcdev->schib_region_offset);
> +
> + if (ret == -1) {
> + /* Assume device is damaged, regardless of errno */
> + return IOINST_CC_NOT_OPERATIONAL;
Not sure that's correct; cc 3 for stsch indicates that there are no
more subchannels with higher ids?
> + }
> +
> + /*
> + * Selectively copy path-related bits of the SCHIB,
> + * rather than copying the entire struct.
> + */
> + schib->pmcw.pnom = s->pmcw.pnom;
> + schib->pmcw.lpum = s->pmcw.lpum;
> + schib->pmcw.pam = s->pmcw.pam;
> + schib->pmcw.pom = s->pmcw.pom;
> +
> + if (s->scsw.flags & SCSW_FLAGS_MASK_PNO) {
> + schib->scsw.flags |= SCSW_FLAGS_MASK_PNO;
> + }
> +
> + return IOINST_CC_EXPECTED;
> +}
> +
The rest of the patch looks good to me.
