linux-kernel - Re: [PATCH v4 4/4] vfio: ccw: add traceponits for interesting error paths

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Date:   Wed, 23 May 2018 12:25:55 +0200
From:   Cornelia Huck <cohuck@...hat.com>
To:     Dong Jia Shi <bjsdjshi@...ux.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, borntraeger@...ibm.com, pasic@...ux.ibm.com,
        pmorel@...ux.ibm.com
Subject: Re: [PATCH v4 4/4] vfio: ccw: add traceponits for interesting error
 paths

On Wed, 23 May 2018 04:56:45 +0200
Dong Jia Shi <bjsdjshi@...ux.ibm.com> wrote:

Still s/traceponits/tracepoints/ (can fix up when applying).

> From: Halil Pasic <pasic@...ux.ibm.com>
> 
> Add some tracepoints so we can inspect what is not working as is should.
> 
> Signed-off-by: Halil Pasic <pasic@...ux.ibm.com>
> Signed-off-by: Dong Jia Shi <bjsdjshi@...ux.ibm.com>
> ---
>  drivers/s390/cio/Makefile         |  1 +
>  drivers/s390/cio/vfio_ccw_fsm.c   | 17 +++++++++++-
>  drivers/s390/cio/vfio_ccw_trace.h | 54 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 71 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/s390/cio/vfio_ccw_trace.h
> 
> diff --git a/drivers/s390/cio/Makefile b/drivers/s390/cio/Makefile
> index a070ef0efe65..f230516abb96 100644
> --- a/drivers/s390/cio/Makefile
> +++ b/drivers/s390/cio/Makefile
> @@ -5,6 +5,7 @@
>  
>  # The following is required for define_trace.h to find ./trace.h
>  CFLAGS_trace.o := -I$(src)
> +CFLAGS_vfio_ccw_fsm.o := -I$(src)
>  
>  obj-y += airq.o blacklist.o chsc.o cio.o css.o chp.o idset.o isc.o \
>  	fcx.o itcw.o crw.o ccwreq.o trace.o ioasm.o
> diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c
> index 3c800642134e..797a82731159 100644
> --- a/drivers/s390/cio/vfio_ccw_fsm.c
> +++ b/drivers/s390/cio/vfio_ccw_fsm.c
> @@ -13,6 +13,9 @@
>  #include "ioasm.h"
>  #include "vfio_ccw_private.h"
>  
> +#define CREATE_TRACE_POINTS
> +#include "vfio_ccw_trace.h"
> +
>  static int fsm_io_helper(struct vfio_ccw_private *private)
>  {
>  	struct subchannel *sch;
> @@ -110,6 +113,10 @@ static void fsm_disabled_irq(struct vfio_ccw_private *private,
>  	 */
>  	cio_disable_subchannel(sch);
>  }
> +inline struct subchannel_id get_schid(struct vfio_ccw_private *p)
> +{
> +	return p->sch->schid;
> +}
>  
>  /*
>   * Deal with the ccw command request from the userspace.
> @@ -121,6 +128,7 @@ static void fsm_io_request(struct vfio_ccw_private *private,
>  	union scsw *scsw = &private->scsw;
>  	struct ccw_io_region *io_region = &private->io_region;
>  	struct mdev_device *mdev = private->mdev;
> +	char *errstr = "request";
>  
>  	private->state = VFIO_CCW_STATE_BOXED;
>  
> @@ -132,15 +140,19 @@ static void fsm_io_request(struct vfio_ccw_private *private,
>  		/* Don't try to build a cp if transport mode is specified. */
>  		if (orb->tm.b) {
>  			io_region->ret_code = -EOPNOTSUPP;
> +			errstr = "transport mode";
>  			goto err_out;
>  		}
>  		io_region->ret_code = cp_init(&private->cp, mdev_dev(mdev),
>  					      orb);
> -		if (io_region->ret_code)
> +		if (io_region->ret_code) {
> +			errstr = "cp init";
>  			goto err_out;
> +		}
>  
>  		io_region->ret_code = cp_prefetch(&private->cp);
>  		if (io_region->ret_code) {
> +			errstr = "cp prefetch";
>  			cp_free(&private->cp);
>  			goto err_out;
>  		}
> @@ -148,6 +160,7 @@ static void fsm_io_request(struct vfio_ccw_private *private,
>  		/* Start channel program and wait for I/O interrupt. */
>  		io_region->ret_code = fsm_io_helper(private);
>  		if (io_region->ret_code) {
> +			errstr = "cp fsm_io_helper";
>  			cp_free(&private->cp);
>  			goto err_out;
>  		}
> @@ -164,6 +177,8 @@ static void fsm_io_request(struct vfio_ccw_private *private,
>  
>  err_out:
>  	private->state = VFIO_CCW_STATE_IDLE;
> +	trace_vfio_ccw_io_fctl(scsw->cmd.fctl, get_schid(private),
> +			       io_region->ret_code, errstr);
>  }
>  
>  /*

This approach looks reasonable to me. We can still improve this later,
should we want to.