On Fri, 31 Jan 2020 15:15:00 -0500 Eric Farman <[email protected]> wrote:
> [Had two un-addressed QEMU comments on my todo list; let's do that now.] > > On 11/20/19 6:13 AM, Cornelia Huck wrote: > > On Fri, 15 Nov 2019 04:34:34 +0100 > > Eric Farman <[email protected]> wrote: Oh, that was some time ago... hope I can still recall what I was thinking back then. > > > >> From: Farhan Ali <[email protected]> > >> > >> 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 <[email protected]> > >> Signed-off-by: Eric Farman <[email protected]> > >> --- > >> > >> 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? > > Might make things a little cleaner, but I am not sure. I'm going to > leave a todo here while we sort out the rest of the kernel code, so I > can try to put something more beneficial together. Yes, this looks like something that can be sorted out later. What bothers me most here, I guess, is that it is not very obvious why the functions above can assume the presence of the cdc object, while this one can't. The secret sauce is in the different do_subchannel_work_* callbacks, which reside in another file... maybe amend the comment here to mention that? That would help and doesn't involve code refactoring :) > > > > > (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? > > POPS says cc=3 on stsch if the subchannel is not operational, and it's > not operational if it's not provided to the channel subsystem. So, > basically yes. I guess his idea was to call out a problem on the kvm > side, so should we just return CC_EXPECTED here, as if there's no region? Yes, that looks like the better choice (out of the two possible condition codes...) And also log a moan somewhere? > > > > >> + } > >> + > >> + /* > >> + * 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. > > >
