Subject: Re: [PATCH v5 27/29] vfio: powerpc/spapr: powerpc/powernv/ioda2: Rework ownership

From: Alex Williamson <[email-masked]>
Date: Tue, 10 Mar 2015 18:09:17 -0600

On Tue, 2015-03-10 at 01:07 +1100, Alexey Kardashevskiy wrote:
> Before the IOMMU user would take control over the IOMMU table belonging to
> a specific IOMMU group. This approach did not allow sharing tables between
> IOMMU groups attached to the same container.
> 
> This introduces a new IOMMU ownership flavour when the user can not
> just control the existing IOMMU table but remove/create tables on demand.
> If an IOMMU supports a set_ownership() callback, that lets the user have
> full control over the IOMMU group. When the ownership is taken,
> the platform code removes all the windows so the caller must create them.
> Before returning the ownership back to the platform code, the user
> has to unprogram and remove all the tables it created.

We have no ability to enforce that requirement on the user.  VFIO needs
to do the cleanup if the user fails to.

> Old-style ownership is still supported allowing VFIO to run on older
> P5IOC2 and IODA IO controllers.
> 
> Signed-off-by: Alexey Kardashevskiy <[email-masked]>
> ---
>  arch/powerpc/platforms/powernv/pci-ioda.c | 30 +++++++++++++++---
>  drivers/vfio/vfio_iommu_spapr_tce.c       | 51 ++++++++++++++++++++++++-------
>  2 files changed, 66 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
> index 07857c4..afb6906 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -1620,11 +1620,33 @@ static void pnv_ioda2_set_ownership(struct iommu_table_group *table_group,
>  {
>  	struct pnv_ioda_pe *pe = container_of(table_group, struct pnv_ioda_pe,
>  						table_group);
> -	if (enable)
> -		iommu_take_ownership(table_group);
> -	else
> -		iommu_release_ownership(table_group);
> +	if (enable) {
> +		pnv_pci_ioda2_unset_window(&pe->table_group, 0);
> +		pnv_pci_free_table(&pe->table_group.tables[0]);
> +	} else {
> +		struct iommu_table *tbl = &pe->table_group.tables[0];
> +		int64_t rc;
>  
> +		rc = pnv_pci_ioda2_create_table(&pe->table_group, 0,
> +				IOMMU_PAGE_SHIFT_4K,
> +				pe->phb->ioda.m32_pci_base,
> +				POWERNV_IOMMU_DEFAULT_LEVELS, tbl);
> +		if (rc) {
> +			pe_err(pe, "Failed to create 32-bit TCE table, err %ld",
> +					rc);
> +			return;
> +		}
> +
> +		iommu_init_table(tbl, pe->phb->hose->node);
> +
> +		rc = pnv_pci_ioda2_set_window(&pe->table_group, 0, tbl);
> +		if (rc) {
> +			pe_err(pe, "Failed to configure 32-bit TCE table, err %ld\n",
> +					rc);
> +			pnv_pci_free_table(tbl);
> +			return;
> +		}
> +	}
>  	pnv_pci_ioda2_set_bypass(pe, !enable);
>  }
>  
> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> index d665ddc..3bc0645 100644
> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> @@ -426,18 +426,11 @@ static int tce_iommu_clear(struct tce_container *container,
>  static void tce_iommu_release(void *iommu_data)
>  {
>  	struct tce_container *container = iommu_data;
> -	struct iommu_table *tbl;
> -	struct iommu_table_group *table_group;
>  
>  	WARN_ON(container->grp);
>  
> -	if (container->grp) {
> -		table_group = iommu_group_get_iommudata(container->grp);
> -		tbl = &table_group->tables[0];
> -		tce_iommu_clear(container, tbl,	tbl->it_offset, tbl->it_size);
> -
> +	if (container->grp)
>  		tce_iommu_detach_group(iommu_data, container->grp);
> -	}
>  
>  	tce_mem_unregister_all(container);
>  	tce_iommu_disable(container);
> @@ -826,14 +819,24 @@ static int tce_iommu_attach_group(void *iommu_data,
>  
>  	if (!table_group->ops || !table_group->ops->set_ownership) {
>  		ret = iommu_take_ownership(table_group);
> +	} else if (!table_group->ops->create_table ||
> +			!table_group->ops->set_window) {
> +		WARN_ON_ONCE(1);
> +		ret = -EFAULT;
>  	} else {
>  		/*
>  		 * Disable iommu bypass, otherwise the user can DMA to all of
>  		 * our physical memory via the bypass window instead of just
>  		 * the pages that has been explicitly mapped into the iommu
>  		 */
> +		struct iommu_table tbltmp = { 0 }, *tbl = &tbltmp;
> +
>  		table_group->ops->set_ownership(table_group, true);
> -		ret = 0;
> +		ret = table_group->ops->create_table(table_group, 0,
> +				IOMMU_PAGE_SHIFT_4K,
> +				table_group->tce32_size, 1, tbl);
> +		if (!ret)
> +			ret = table_group->ops->set_window(table_group, 0, tbl);
>  	}
>  
>  	if (ret)
> @@ -852,6 +855,7 @@ static void tce_iommu_detach_group(void *iommu_data,
>  {
>  	struct tce_container *container = iommu_data;
>  	struct iommu_table_group *table_group;
> +	long i;
>  
>  	mutex_lock(&container->lock);
>  	if (iommu_group != container->grp) {
> @@ -875,10 +879,35 @@ static void tce_iommu_detach_group(void *iommu_data,
>  	BUG_ON(!table_group);
>  
>  	/* Kernel owns the device now, we can restore bypass */
> -	if (!table_group->ops || !table_group->ops->set_ownership)
> +	if (!table_group->ops || !table_group->ops->set_ownership) {
> +		for (i = 0; i < IOMMU_TABLE_GROUP_MAX_TABLES; ++i) {
> +			struct iommu_table *tbl = &table_group->tables[i];
> +
> +			if (!tbl->it_size)
> +				continue;
> +
> +			if (!tbl->it_ops)
> +				goto unlock_exit;
> +			tce_iommu_clear(container, tbl,
> +					tbl->it_offset, tbl->it_size);
> +		}
>  		iommu_release_ownership(table_group);
> -	else
> +	} else if (!table_group->ops->unset_window) {
> +		WARN_ON_ONCE(1);
> +	} else {
> +		for (i = 0; i < IOMMU_TABLE_GROUP_MAX_TABLES; ++i) {
> +			struct iommu_table *tbl = &table_group->tables[i];
> +
> +			table_group->ops->unset_window(table_group, i);
> +			tce_iommu_clear(container, tbl,
> +					tbl->it_offset, tbl->it_size);
> +
> +			if (tbl->it_ops->free)
> +				tbl->it_ops->free(tbl);
> +		}
> +
>  		table_group->ops->set_ownership(table_group, false);
> +	}
>  
>  unlock_exit:
>