Subject: Re: [PATCH v3 08/24] powerpc/spapr: vfio: Switch from iommu_table to new powerpc_iommu

From: Alex Williamson <[email-masked]>
Date: Mon, 02 Feb 2015 17:12:45 -0700

On Thu, 2015-01-29 at 20:21 +1100, Alexey Kardashevskiy wrote:
> Modern IBM POWERPC systems support multiple (currently two) TCE tables
> per IOMMU group (a.k.a. PE). This adds a powerpc_iommu container
> for TCE tables. Right now just one table is supported.
> 
> Signed-off-by: Alexey Kardashevskiy <[email-masked]>
> ---
>  arch/powerpc/include/asm/iommu.h            |  18 ++--
>  arch/powerpc/kernel/eeh.c                   |   2 +-
>  arch/powerpc/kernel/iommu.c                 |  34 ++++----
>  arch/powerpc/platforms/powernv/pci-ioda.c   |  37 +++++---
>  arch/powerpc/platforms/powernv/pci-p5ioc2.c |  16 ++--
>  arch/powerpc/platforms/powernv/pci.c        |   2 +-
>  arch/powerpc/platforms/powernv/pci.h        |   4 +-
>  arch/powerpc/platforms/pseries/iommu.c      |   9 +-
>  drivers/vfio/vfio_iommu_spapr_tce.c         | 131 ++++++++++++++++++++--------
>  9 files changed, 170 insertions(+), 83 deletions(-)
[snip]
> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> index 29d5708..28909e1 100644
> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> @@ -84,7 +84,7 @@ static void decrement_locked_vm(long npages)
>   */
>  struct tce_container {
>  	struct mutex lock;
> -	struct iommu_table *tbl;
> +	struct iommu_group *grp;
>  	bool enabled;
>  };
>  
> @@ -104,16 +104,40 @@ static bool tce_check_page_size(struct page *page, unsigned page_shift)
>  	return false;
>  }
>  
> +static struct iommu_table *spapr_tce_find_table(
> +		struct tce_container *container,
> +		phys_addr_t ioba)
> +{
> +	long i;
> +	struct iommu_table *ret = NULL;
> +	struct powerpc_iommu *iommu = iommu_group_get_iommudata(container->grp);
> +
> +	mutex_lock(&container->lock);
> +	for (i = 0; i < POWERPC_IOMMU_MAX_TABLES; ++i) {
> +		struct iommu_table *tbl = &iommu->tables[i];
> +		unsigned long entry = ioba >> tbl->it_page_shift;
> +		unsigned long start = tbl->it_offset;
> +		unsigned long end = start + tbl->it_size;
> +
> +		if ((start <= entry) && (entry < end)) {
> +			ret = tbl;
> +			break;
> +		}
> +	}
> +	mutex_unlock(&container->lock);
> +
> +	return ret;
> +}
> +
>  static int tce_iommu_enable(struct tce_container *container)
>  {
>  	int ret = 0;
> +	struct powerpc_iommu *iommu;
> +	struct iommu_table *tbl;
>  
> -	if (!container->tbl)
> +	if (!container->grp)
>  		return -ENXIO;
>  
> -	if (!current->mm)
> -		return -ESRCH; /* process exited */
> -
>  	if (container->enabled)
>  		return -EBUSY;
>  
> @@ -142,7 +166,12 @@ static int tce_iommu_enable(struct tce_container *container)
>  	 * as this information is only available from KVM and VFIO is
>  	 * KVM agnostic.
>  	 */
> -	ret = try_increment_locked_vm(IOMMU_TABLE_PAGES(container->tbl));
> +	iommu = iommu_group_get_iommudata(container->grp);
> +	if (!iommu)
> +		return -EFAULT;
> +
> +	tbl = &iommu->tables[0];

There should probably be a comment somewhere documenting that tables[0]
is the small window and presumably [1] will be the DDW.