Re: [PULL 13/14] vfio-ccw: Factor out the ccw0-to-ccw1 transition

[Eric Farman <farman@linux.ibm.com>]

Conny,

I'm bad at things, because I thought for sure I had checked for and
fixed this before I sent the patches.  This one gets a sparse warning,
fixed below.

Eric

On 6/21/19 10:33 AM, Cornelia Huck wrote:
> From: Eric Farman <farman@linux.ibm.com>
> 
> This is a really useful function, but it's buried in the
> copy_ccw_from_iova() routine so that ccwchain_calc_length()
> can just work with Format-1 CCWs while doing its counting.
> But it means we're translating a full 2K of "CCWs" to Format-1,
> when in reality there's probably far fewer in that space.
> 
> Let's factor it out, so maybe we can do something with it later.
> 
> Signed-off-by: Eric Farman <farman@linux.ibm.com>
> Message-Id: <20190618202352.39702-5-farman@linux.ibm.com>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
> Reviewed-by: Farhan Ali <alifm@linux.ibm.com>
> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> ---
>  drivers/s390/cio/vfio_ccw_cp.c | 48 ++++++++++++++++++----------------
>  1 file changed, 25 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
> index a55f8d110920..9a8bf06281e0 100644
> --- a/drivers/s390/cio/vfio_ccw_cp.c
> +++ b/drivers/s390/cio/vfio_ccw_cp.c
> @@ -161,6 +161,27 @@ static inline void pfn_array_idal_create_words(
>  	idaws[0] += pa->pa_iova & (PAGE_SIZE - 1);
>  }
>  
> +void convert_ccw0_to_ccw1(struct ccw1 *source, unsigned long len)

static void convert_...

> +{
> +	struct ccw0 ccw0;
> +	struct ccw1 *pccw1 = source;
> +	int i;
> +
> +	for (i = 0; i < len; i++) {
> +		ccw0 = *(struct ccw0 *)pccw1;
> +		if ((pccw1->cmd_code & 0x0f) == CCW_CMD_TIC) {
> +			pccw1->cmd_code = CCW_CMD_TIC;
> +			pccw1->flags = 0;
> +			pccw1->count = 0;
> +		} else {
> +			pccw1->cmd_code = ccw0.cmd_code;
> +			pccw1->flags = ccw0.flags;
> +			pccw1->count = ccw0.count;
> +		}
> +		pccw1->cda = ccw0.cda;
> +		pccw1++;
> +	}
> +}
>  
>  /*
>   * Within the domain (@mdev), copy @n bytes from a guest physical
> @@ -211,32 +232,9 @@ static long copy_ccw_from_iova(struct channel_program *cp,
>  			       struct ccw1 *to, u64 iova,
>  			       unsigned long len)
>  {
> -	struct ccw0 ccw0;
> -	struct ccw1 *pccw1;
>  	int ret;
> -	int i;
>  
>  	ret = copy_from_iova(cp->mdev, to, iova, len * sizeof(struct ccw1));
> -	if (ret)
> -		return ret;
> -
> -	if (!cp->orb.cmd.fmt) {
> -		pccw1 = to;
> -		for (i = 0; i < len; i++) {
> -			ccw0 = *(struct ccw0 *)pccw1;
> -			if ((pccw1->cmd_code & 0x0f) == CCW_CMD_TIC) {
> -				pccw1->cmd_code = CCW_CMD_TIC;
> -				pccw1->flags = 0;
> -				pccw1->count = 0;
> -			} else {
> -				pccw1->cmd_code = ccw0.cmd_code;
> -				pccw1->flags = ccw0.flags;
> -				pccw1->count = ccw0.count;
> -			}
> -			pccw1->cda = ccw0.cda;
> -			pccw1++;
> -		}
> -	}
>  
>  	return ret;
>  }
> @@ -441,6 +439,10 @@ static int ccwchain_handle_ccw(u32 cda, struct channel_program *cp)
>  	if (len)
>  		return len;
>  
> +	/* Convert any Format-0 CCWs to Format-1 */
> +	if (!cp->orb.cmd.fmt)
> +		convert_ccw0_to_ccw1(cp->guest_cp, len);
> +
>  	/* Count the CCWs in the current chain */
>  	len = ccwchain_calc_length(cda, cp);
>  	if (len < 0)
>