Subject: Re: [PATCH kernel v9 09/32] vfio: powerpc/spapr: Rework groups attaching

From: David Gibson <[email-masked]>
Date: Wed, 29 Apr 2015 12:16:18 +1000

On Sat, Apr 25, 2015 at 10:14:33PM +1000, Alexey Kardashevskiy wrote:
> This is to make extended ownership and multiple groups support patches
> simpler for review.
> 
> This should cause no behavioural change.

Um.. this doesn't appear to be true.  Previously removing a group from
an enabled container would fail with EBUSY, now it forces a disable.

> 
> Signed-off-by: Alexey Kardashevskiy <[email-masked]>
> [aw: for the vfio related changes]
> Acked-by: Alex Williamson <[email-masked]>
> Reviewed-by: David Gibson <[email-masked]>
> ---
>  drivers/vfio/vfio_iommu_spapr_tce.c | 40 ++++++++++++++++++++++---------------
>  1 file changed, 24 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> index 115d5e6..0fbe03e 100644
> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> @@ -460,16 +460,21 @@ static int tce_iommu_attach_group(void *iommu_data,
>  				iommu_group_id(container->tbl->it_group),
>  				iommu_group_id(iommu_group));
>  		ret = -EBUSY;
> -	} else if (container->enabled) {
> +		goto unlock_exit;
> +	}
> +
> +	if (container->enabled) {
>  		pr_err("tce_vfio: attaching group #%u to enabled container\n",
>  				iommu_group_id(iommu_group));
>  		ret = -EBUSY;
> -	} else {
> -		ret = iommu_take_ownership(tbl);
> -		if (!ret)
> -			container->tbl = tbl;
> +		goto unlock_exit;
>  	}
>  
> +	ret = iommu_take_ownership(tbl);
> +	if (!ret)
> +		container->tbl = tbl;
> +
> +unlock_exit:
>  	mutex_unlock(&container->lock);
>  
>  	return ret;
> @@ -487,19 +492,22 @@ static void tce_iommu_detach_group(void *iommu_data,
>  		pr_warn("tce_vfio: detaching group #%u, expected group is #%u\n",
>  				iommu_group_id(iommu_group),
>  				iommu_group_id(tbl->it_group));
> -	} else {
> -		if (container->enabled) {
> -			pr_warn("tce_vfio: detaching group #%u from enabled container, forcing disable\n",
> -					iommu_group_id(tbl->it_group));
> -			tce_iommu_disable(container);
> -		}
> +		goto unlock_exit;
> +	}
>  
> -		/* pr_debug("tce_vfio: detaching group #%u from iommu %p\n",
> -				iommu_group_id(iommu_group), iommu_group); */
> -		container->tbl = NULL;
> -		tce_iommu_clear(container, tbl, tbl->it_offset, tbl->it_size);
> -		iommu_release_ownership(tbl);
> +	if (container->enabled) {
> +		pr_warn("tce_vfio: detaching group #%u from enabled container, forcing disable\n",
> +				iommu_group_id(tbl->it_group));
> +		tce_iommu_disable(container);
>  	}
> +
> +	/* pr_debug("tce_vfio: detaching group #%u from iommu %p\n",
> +	   iommu_group_id(iommu_group), iommu_group); */
> +	container->tbl = NULL;
> +	tce_iommu_clear(container, tbl, tbl->it_offset, tbl->it_size);
> +	iommu_release_ownership(tbl);
> +
> +unlock_exit:
>  	mutex_unlock(&container->lock);
>  }
>  

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson