Re: [PATCH v2 04/13] powerpc/powernv: Convert/move set_bypass() callback to take_ownership()

[Alex Williamson <alex.williamson@redhat.com>]

On Tue, 2014-09-23 at 13:00 +1000, Alexey Kardashevskiy wrote:
> At the moment the iommu_table struct has a set_bypass() which enables/
> disables DMA bypass on IODA2 PHB. This is exposed to POWERPC IOMMU code
> which calls this callback when external IOMMU users such as VFIO are
> about to get over a PHB.
> 
> Since the set_bypass() is not really an iommu_table function but PE's
> function, and we have an ops struct per IOMMU owner, let's move
> set_bypass() to the spapr_tce_iommu_ops struct.
> 
> As arch/powerpc/kernel/iommu.c is more about POWERPC IOMMU tables and
> has very little to do with PEs, this moves take_ownership() calls to
> the VFIO SPAPR TCE driver.
> 
> This renames set_bypass() to take_ownership() as it is not necessarily
> just enabling bypassing, it can be something else/more so let's give it
> a generic name. The bool parameter is inverted.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
> ---
>  arch/powerpc/include/asm/iommu.h          |  1 -
>  arch/powerpc/include/asm/tce.h            |  2 ++
>  arch/powerpc/kernel/iommu.c               | 12 ------------
>  arch/powerpc/platforms/powernv/pci-ioda.c | 20 ++++++++++++--------
>  drivers/vfio/vfio_iommu_spapr_tce.c       | 16 ++++++++++++++++
>  5 files changed, 30 insertions(+), 21 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
> index 84ee339..2b0b01d 100644
> --- a/arch/powerpc/include/asm/iommu.h
> +++ b/arch/powerpc/include/asm/iommu.h
> @@ -77,7 +77,6 @@ struct iommu_table {
>  #ifdef CONFIG_IOMMU_API
>  	struct iommu_group *it_group;
>  #endif
> -	void (*set_bypass)(struct iommu_table *tbl, bool enable);
>  };
>  
>  /* Pure 2^n version of get_order */
> diff --git a/arch/powerpc/include/asm/tce.h b/arch/powerpc/include/asm/tce.h
> index 9f159eb..e6355f9 100644
> --- a/arch/powerpc/include/asm/tce.h
> +++ b/arch/powerpc/include/asm/tce.h
> @@ -56,6 +56,8 @@ struct spapr_tce_iommu_ops {
>  	struct iommu_table *(*get_table)(
>  			struct spapr_tce_iommu_group *data,
>  			int num);
> +	void (*take_ownership)(struct spapr_tce_iommu_group *data,
> +			bool enable);

"set" is a better verb when using a bool to specify direction, imho.

This is pretty confusing now that we have

iommu_take_ownership()
data->ops->take_ownership(true)

iommu_release_ownership()
data->ops->take_ownership(false)

And there's zero comments here about what take_ownership is supposed to
provide, or get_table for that matter.

>  };
>  
>  struct spapr_tce_iommu_group {
> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
> index 1c5dae7..c2c8d9d 100644
> --- a/arch/powerpc/kernel/iommu.c
> +++ b/arch/powerpc/kernel/iommu.c
> @@ -1139,14 +1139,6 @@ int iommu_take_ownership(struct iommu_table *tbl)
>  	memset(tbl->it_map, 0xff, sz);
>  	iommu_clear_tces_and_put_pages(tbl, tbl->it_offset, tbl->it_size);
>  
> -	/*
> -	 * 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
> -	 */
> -	if (tbl->set_bypass)
> -		tbl->set_bypass(tbl, false);
> -
>  	return 0;
>  }
>  EXPORT_SYMBOL_GPL(iommu_take_ownership);
> @@ -1161,10 +1153,6 @@ void iommu_release_ownership(struct iommu_table *tbl)
>  	/* Restore bit#0 set by iommu_init_table() */
>  	if (tbl->it_offset == 0)
>  		set_bit(0, tbl->it_map);
> -
> -	/* The kernel owns the device now, we can restore the iommu bypass */
> -	if (tbl->set_bypass)
> -		tbl->set_bypass(tbl, true);
>  }
>  EXPORT_SYMBOL_GPL(iommu_release_ownership);
>  
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
> index 2d32a1c..8cb2f31 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -1105,10 +1105,8 @@ static void pnv_pci_ioda_setup_dma_pe(struct pnv_phb *phb,
>  		__free_pages(tce_mem, get_order(TCE32_TABLE_SIZE * segs));
>  }
>  
> -static void pnv_pci_ioda2_set_bypass(struct iommu_table *tbl, bool enable)
> +static void pnv_pci_ioda2_set_bypass(struct pnv_ioda_pe *pe, bool enable)
>  {
> -	struct pnv_ioda_pe *pe = container_of(tbl, struct pnv_ioda_pe,
> -					      tce32.table);
>  	uint16_t window_id = (pe->pe_number << 1 ) + 1;
>  	int64_t rc;
>  
> @@ -1136,7 +1134,7 @@ static void pnv_pci_ioda2_set_bypass(struct iommu_table *tbl, bool enable)
>  		 * host side.
>  		 */
>  		if (pe->pdev)
> -			set_iommu_table_base(&pe->pdev->dev, tbl);
> +			set_iommu_table_base(&pe->pdev->dev, &pe->tce32.table);
>  		else
>  			pnv_ioda_setup_bus_dma(pe, pe->pbus, false);
>  	}
> @@ -1152,15 +1150,21 @@ static void pnv_pci_ioda2_setup_bypass_pe(struct pnv_phb *phb,
>  	/* TVE #1 is selected by PCI address bit 59 */
>  	pe->tce_bypass_base = 1ull << 59;
>  
> -	/* Install set_bypass callback for VFIO */
> -	pe->tce32.table.set_bypass = pnv_pci_ioda2_set_bypass;
> -
>  	/* Enable bypass by default */
> -	pnv_pci_ioda2_set_bypass(&pe->tce32.table, true);
> +	pnv_pci_ioda2_set_bypass(pe, true);
> +}
> +
> +static void pnv_ioda2_take_ownership(struct spapr_tce_iommu_group *data,
> +				     bool enable)
> +{
> +	struct pnv_ioda_pe *pe = data->iommu_owner;
> +
> +	pnv_pci_ioda2_set_bypass(pe, !enable);
>  }
>  
>  static struct spapr_tce_iommu_ops pnv_pci_ioda2_ops = {
>  	.get_table = pnv_ioda1_iommu_get_table,
> +	.take_ownership = pnv_ioda2_take_ownership,
>  };
>  
>  static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> index a8adfbd..1c1a9c4 100644
> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> @@ -76,6 +76,13 @@ static struct iommu_table *spapr_tce_find_table(
>  	return ret;
>  }
>  
> +static void tce_iommu_take_ownership_notify(struct spapr_tce_iommu_group *data,
> +		bool enable)
> +{
> +	if (data && data->ops && data->ops->take_ownership)
> +		data->ops->take_ownership(data, enable);
> +}
> +
>  static int tce_iommu_enable(struct tce_container *container)
>  {
>  	int ret = 0;
> @@ -413,6 +420,12 @@ static int tce_iommu_attach_group(void *iommu_data,
>  		ret = iommu_take_ownership(tbl);
>  		if (!ret)
>  			container->grp = iommu_group;
> +		/*
> +		 * 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
> +		 */
> +		tce_iommu_take_ownership_notify(data, true);
>  	}
>  
>  	mutex_unlock(&container->lock);
> @@ -450,6 +463,9 @@ static void tce_iommu_detach_group(void *iommu_data,
>  		BUG_ON(!tbl);
>  
>  		iommu_release_ownership(tbl);
> +
> +		/* Kernel owns the device now, we can restore bypass */
> +		tce_iommu_take_ownership_notify(data, false);
>  	}
>  	mutex_unlock(&container->lock);
>  }