Subject: Re: [PATCH v3 10/18] powerpc/powernv: Convert/move set_bypass() callback to take_ownership()

From: Benjamin Herrenschmidt <[email-masked]>
Date: Mon, 28 Jul 2014 11:18:55 +1000

On Thu, 2014-07-24 at 18:48 +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.

I disagree with the name change. take_ownership() is the right semantic
at the high level, but down to the actual table, it *is* about disabling
bypass.

> Signed-off-by: Alexey Kardashevskiy <[email-masked]>
> Reviewed-by: Gavin Shan <[email-masked]>
> ---
>  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 | 18 +++++++++++-------
>  drivers/vfio/vfio_iommu_spapr_tce.c       | 16 ++++++++++++++++
>  5 files changed, 29 insertions(+), 20 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 8bfe98f..5ee4987 100644
> --- a/arch/powerpc/include/asm/tce.h
> +++ b/arch/powerpc/include/asm/tce.h
> @@ -58,6 +58,8 @@ struct spapr_tce_iommu_ops {
>  	struct iommu_table *(*get_table)(
>  			struct spapr_tce_iommu_group *data,
>  			phys_addr_t addr);
> +	void (*take_ownership)(struct spapr_tce_iommu_group *data,
> +			bool enable);
>  };
>  
>  struct spapr_tce_iommu_group {
> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
> index e203314..06984d5 100644
> --- a/arch/powerpc/kernel/iommu.c
> +++ b/arch/powerpc/kernel/iommu.c
> @@ -1116,14 +1116,6 @@ 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);
> @@ -1138,10 +1130,6 @@ 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 495137b..f828c57 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -709,10 +709,8 @@ 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;
>  
> @@ -752,15 +750,21 @@ 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 917c854..05b2f11 100644
> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> @@ -78,6 +78,13 @@ static long tce_iommu_account_memlimit(struct iommu_table *tbl, bool inc)
>  	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;
> @@ -386,6 +393,12 @@ 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);
> @@ -423,6 +436,9 @@ 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);
>  }