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 14:19:55 +1000

On Mon, 2014-07-28 at 13:55 +1000, Alexey Kardashevskiy wrote:
> On 07/28/2014 11:18 AM, Benjamin Herrenschmidt wrote:
> > 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.
> 
> It is still pnv_pci_ioda2_set_bypass() :-/
> 
> take_ownership() is a callback of PNV IOMMU group.
> 
> s/take_ownership/set_bypass/ ?
> 

Hrm, ... ok. It's a bit messy but should do for now.

> > 
> >> 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);
> >>  }
> > 
> > 
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> > 
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