Re: [PATCH 2/2] vfio-ccw: support async command subregion

[Pierre Morel <pmorel@linux.ibm.com>]

On 22/11/2018 17:54, Cornelia Huck wrote:
> A vfio-ccw device may provide an async command subregion for
> issuing halt/clear subchannel requests. If it is present, use
> it for sending halt/clear request to the device; if not, fall
> back to emulation (as done today).
> 
> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> ---
>   hw/s390x/css.c              |  27 +++++++--
>   hw/vfio/ccw.c               | 109 +++++++++++++++++++++++++++++++++++-
>   include/hw/s390x/s390-ccw.h |   3 +
>   3 files changed, 133 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/s390x/css.c b/hw/s390x/css.c
> index 04ec5cc970..0897c041c5 100644
> --- a/hw/s390x/css.c
> +++ b/hw/s390x/css.c
> @@ -22,6 +22,7 @@
>   #include "trace.h"
>   #include "hw/s390x/s390_flic.h"
>   #include "hw/s390x/s390-virtio-ccw.h"
> +#include "hw/s390x/s390-ccw.h"
>   
>   typedef struct CrwContainer {
>       CRW crw;
> @@ -1194,6 +1195,26 @@ static void sch_handle_start_func_virtual(SubchDev *sch)
>   
>   }
>   
> +static void sch_handle_halt_func_passthrough(SubchDev *sch)
> +{
> +    int ret;
> +
> +    ret = vfio_ccw_handle_halt(sch);
> +    if (ret == -ENOSYS) {
> +        sch_handle_halt_func(sch);
> +    }
> +}
> +
> +static void sch_handle_clear_func_passthrough(SubchDev *sch)
> +{
> +    int ret;
> +
> +    ret = vfio_ccw_handle_clear(sch);
> +    if (ret == -ENOSYS) {
> +        sch_handle_clear_func(sch);
> +    }
> +}
> +
>   static IOInstEnding sch_handle_start_func_passthrough(SubchDev *sch)
>   {
>   
> @@ -1237,11 +1258,9 @@ IOInstEnding do_subchannel_work_passthrough(SubchDev *sch)
>       SCSW *s = &sch->curr_status.scsw;
>   
>       if (s->ctrl & SCSW_FCTL_CLEAR_FUNC) {
> -        /* TODO: Clear handling */
> -        sch_handle_clear_func(sch);
> +        sch_handle_clear_func_passthrough(sch);
>       } else if (s->ctrl & SCSW_FCTL_HALT_FUNC) {
> -        /* TODO: Halt handling */
> -        sch_handle_halt_func(sch);
> +        sch_handle_halt_func_passthrough(sch);
>       } else if (s->ctrl & SCSW_FCTL_START_FUNC) {
>           return sch_handle_start_func_passthrough(sch);
>       }
> diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
> index 9246729a75..dd0fecf168 100644
> --- a/hw/vfio/ccw.c
> +++ b/hw/vfio/ccw.c
> @@ -2,9 +2,12 @@
>    * vfio based subchannel assignment support
>    *
>    * Copyright 2017 IBM Corp.
> + * Copyright 2018 Red Hat, Inc.
> + *
>    * Author(s): Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
>    *            Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
>    *            Pierre Morel <pmorel@linux.vnet.ibm.com>
> + *            Cornelia Huck <cohuck@redhat.com>
>    *
>    * This work is licensed under the terms of the GNU GPL, version 2 or (at
>    * your option) any later version. See the COPYING file in the top-level
> @@ -32,6 +35,9 @@ typedef struct VFIOCCWDevice {
>       uint64_t io_region_size;
>       uint64_t io_region_offset;
>       struct ccw_io_region *io_region;
> +    uint64_t async_cmd_region_size;
> +    uint64_t async_cmd_region_offset;
> +    struct ccw_cmd_region *async_cmd_region;
>       EventNotifier io_notifier;
>       bool force_orb_pfch;
>       bool warned_orb_pfch;
> @@ -114,6 +120,87 @@ again:
>       }
>   }
>   
> +int vfio_ccw_handle_clear(SubchDev *sch)
> +{
> +    S390CCWDevice *cdev = sch->driver_data;
> +    VFIOCCWDevice *vcdev = DO_UPCAST(VFIOCCWDevice, cdev, cdev);
> +    struct ccw_cmd_region *region = vcdev->async_cmd_region;
> +    int ret;
> +
> +    if (!vcdev->async_cmd_region) {
> +        /* Async command region not available, fall back to emulation */
> +        return -ENOSYS;
> +    }
> +
> +    memset(region, 0, sizeof(*region));
> +    region->command = VFIO_CCW_ASYNC_CMD_CSCH;
> +
> +again:
> +    ret = pwrite(vcdev->vdev.fd, region,
> +                 vcdev->async_cmd_region_size, vcdev->async_cmd_region_offset);
> +    if (ret != vcdev->async_cmd_region_size) {
> +        if (errno == EAGAIN) {


Where do the EAGAIN come from?


> +            goto again;
> +        }
> +        error_report("vfio-ccw: wirte I/O region failed with errno=%d", errno);
> +        ret = -errno;
> +    } else {
> +        ret = region->ret_code;
> +    }
> +    switch (ret) {
> +    case 0:
> +    case -ENODEV:
> +    case -EACCES:

should never happen?

> +        return 0;
> +    case -EFAULT:
> +    default:
> +        sch_gen_unit_exception(sch);
> +        css_inject_io_interrupt(sch);
> +        return 0;
> +    }
> +}
> +

otherwise LGTM

-- 
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany