RE: [PATCH 2/3 v2] iommu/fsl: Enable default DMA window for PCIedevices

[Sethi Varun-B16395]

> -----Original Message-----
> From: Bhushan Bharat-R65777
> Sent: Wednesday, October 16, 2013 10:20 PM
> To: Sethi Varun-B16395; joro@xxxxxxxxxx; iommu@xxxxxxxxxxxx
> foundation.org; linuxppc-dev@xxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; Yoder Stuart-B08248; Wood Scott-B07421;
> alex.williamson@xxxxxxxxxx
> Subject: RE: [PATCH 2/3 v2] iommu/fsl: Enable default DMA window for PCIe
> devices
> 
> 
> 
> > -----Original Message-----
> > From: Sethi Varun-B16395
> > Sent: Wednesday, October 16, 2013 4:53 PM
> > To: joro@xxxxxxxxxx; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; linuxppc-
> > dev@xxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Yoder
> > Stuart-B08248; Wood Scott-B07421; alex.williamson@xxxxxxxxxx; Bhushan
> > Bharat-R65777
> > Cc: Sethi Varun-B16395
> > Subject: [PATCH 2/3 v2] iommu/fsl: Enable default DMA window for PCIe
> > devices
> >
> > Once the PCIe device assigned to a guest VM (via VFIO) gets detached
> > from the iommu domain (when guest terminates), its PAMU table entry is
> > disabled. So, this would prevent the device from being used once it's
> assigned back to the host.
> >
> > This patch allows for creation of a default DMA window corresponding
> > to the device and subsequently enabling the PAMU table entry. Before
> > we enable the entry, we ensure that the device's bus master capability
> > is disabled (device quiesced).
> >
> > Signed-off-by: Varun Sethi <Varun.Sethi@xxxxxxxxxxxxx>
> > ---
> >  drivers/iommu/fsl_pamu.c        |   43 ++++++++++++++++++++++++++++---
> -----
> >  drivers/iommu/fsl_pamu.h        |    1 +
> >  drivers/iommu/fsl_pamu_domain.c |   46
> ++++++++++++++++++++++++++++++++++++---
> >  3 files changed, 78 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/iommu/fsl_pamu.c b/drivers/iommu/fsl_pamu.c index
> > cba0498..fb4a031 100644
> > --- a/drivers/iommu/fsl_pamu.c
> > +++ b/drivers/iommu/fsl_pamu.c
> > @@ -225,6 +225,21 @@ static struct paace *pamu_get_spaace(struct paace
> > *paace,
> > u32 wnum)
> >  	return spaace;
> >  }
> >
> > +/*
> > + * Defaul PPAACE settings for an LIODN.
> > + */
> > +static void setup_default_ppaace(struct paace *ppaace) {
> > +	pamu_init_ppaace(ppaace);
> > +	/* window size is 2^(WSE+1) bytes */
> > +	set_bf(ppaace->addr_bitfields, PPAACE_AF_WSE, 35);
> > +	ppaace->wbah = 0;
> > +	set_bf(ppaace->addr_bitfields, PPAACE_AF_WBAL, 0);
> > +	set_bf(ppaace->impl_attr, PAACE_IA_ATM,
> > +		PAACE_ATM_NO_XLATE);
> > +	set_bf(ppaace->addr_bitfields, PAACE_AF_AP,
> > +		PAACE_AP_PERMS_ALL);
> > +}
> >  /**
> >   * pamu_get_fspi_and_allocate() - Allocates fspi index and reserves
> subwindows
> >   *                                required for primary PAACE in the
> secondary
> > @@ -253,6 +268,24 @@ static unsigned long
> > pamu_get_fspi_and_allocate(u32
> > subwin_cnt)
> >  	return (spaace_addr - (unsigned long)spaact) / (sizeof(struct
> > paace));  }
> >
> > +/* Reset the PAACE entry to the default state */ void
> > +enable_default_dma_window(int liodn) {
> > +	struct paace *ppaace;
> > +
> > +	ppaace = pamu_get_ppaace(liodn);
> > +	if (!ppaace) {
> > +		pr_debug("Invalid liodn entry\n");
> > +		return;
> > +	}
> > +
> > +	memset(ppaace, 0, sizeof(struct paace));
> > +
> > +	setup_default_ppaace(ppaace);
> > +	mb();
> > +	pamu_enable_liodn(liodn);
> > +}
> > +
> >  /* Release the subwindows reserved for a particular LIODN */  void
> > pamu_free_subwins(int liodn)  { @@ -752,15 +785,7 @@ static void
> > __init
> > setup_liodns(void)
> >  				continue;
> >  			}
> >  			ppaace = pamu_get_ppaace(liodn);
> > -			pamu_init_ppaace(ppaace);
> > -			/* window size is 2^(WSE+1) bytes */
> > -			set_bf(ppaace->addr_bitfields, PPAACE_AF_WSE, 35);
> > -			ppaace->wbah = 0;
> > -			set_bf(ppaace->addr_bitfields, PPAACE_AF_WBAL, 0);
> > -			set_bf(ppaace->impl_attr, PAACE_IA_ATM,
> > -				PAACE_ATM_NO_XLATE);
> > -			set_bf(ppaace->addr_bitfields, PAACE_AF_AP,
> > -				PAACE_AP_PERMS_ALL);
> > +			setup_default_ppaace(ppaace);
> >  			if (of_device_is_compatible(node, "fsl,qman-portal"))
> >  				setup_qbman_paace(ppaace, QMAN_PORTAL_PAACE);
> >  			if (of_device_is_compatible(node, "fsl,qman")) diff --
> git
> > a/drivers/iommu/fsl_pamu.h b/drivers/iommu/fsl_pamu.h index
> > 8fc1a12..0edcbbbb
> > 100644
> > --- a/drivers/iommu/fsl_pamu.h
> > +++ b/drivers/iommu/fsl_pamu.h
> > @@ -406,5 +406,6 @@ void get_ome_index(u32 *omi_index, struct device
> > *dev);  int pamu_update_paace_stash(int liodn, u32 subwin, u32 value);
> > int pamu_disable_spaace(int liodn, u32 subwin);
> >  u32 pamu_get_max_subwin_cnt(void);
> > +void enable_default_dma_window(int liodn);
> >
> >  #endif  /* __FSL_PAMU_H */
> > diff --git a/drivers/iommu/fsl_pamu_domain.c
> > b/drivers/iommu/fsl_pamu_domain.c index 966ae70..dd6cafc 100644
> > --- a/drivers/iommu/fsl_pamu_domain.c
> > +++ b/drivers/iommu/fsl_pamu_domain.c
> > @@ -340,17 +340,57 @@ static inline struct device_domain_info
> > *find_domain(struct device *dev)
> >  	return dev->archdata.iommu_domain;
> >  }
> >
> > +/* Disable device DMA capability and enable default DMA window */
> > +static void disable_device_dma(struct device_domain_info *info,
> > +				int enable_dma_window)
> > +{
> > +#ifdef CONFIG_PCI
> > +	if (info->dev->bus == &pci_bus_type) {
> > +		struct pci_dev *pdev = NULL;
> > +		pdev = to_pci_dev(info->dev);
> > +		if (pci_is_enabled(pdev))
> > +			pci_disable_device(pdev);
> > +	}
> > +#endif
> > +
> > +	if (enable_dma_window)
> > +		enable_default_dma_window(info->liodn);
> > +}
> > +
> > +static int check_for_shared_liodn(struct device_domain_info *info) {
> > +	struct device_domain_info *tmp;
> > +
> > +	/*
> > +	 * Sanity check, to ensure that this is not a
> > +	 * shared LIODN. In case of a PCIe controller
> > +	 * it's possible that all PCIe devices share
> > +	 * the same LIODN.
> > +	 */
> > +	list_for_each_entry(tmp, &info->domain->devices, link) {
> > +		if (info->liodn == tmp->liodn)
> > +			return 1;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> >  static void remove_device_ref(struct device_domain_info *info, u32
> win_cnt)  {
> >  	unsigned long flags;
> > +	int enable_dma_window = 0;
> >
> >  	list_del(&info->link);
> >  	spin_lock_irqsave(&iommu_lock, flags);
> > -	if (win_cnt > 1)
> > -		pamu_free_subwins(info->liodn);
> > -	pamu_disable_liodn(info->liodn);
> > +	if (!check_for_shared_liodn(info)) {
> 
> One query; Do we really need to check for this?
> 
[Sethi Varun-B16395] Yes, just a sanity check to ensure that there are no more devices linked to this LIODN and we can disable it.

-Varun

> Otherwise this patch series looks good to me.
> 
> Thanks
> -Bharat
> 
> > +		if (win_cnt > 1)
> > +			pamu_free_subwins(info->liodn);
> > +		pamu_disable_liodn(info->liodn);
> > +		enable_dma_window = 1;
> > +	}
> >  	spin_unlock_irqrestore(&iommu_lock, flags);
> >  	spin_lock_irqsave(&device_domain_lock, flags);
> > +	disable_device_dma(info, enable_dma_window);
> >  	info->dev->archdata.iommu_domain = NULL;
> >  	kmem_cache_free(iommu_devinfo_cache, info);
> >  	spin_unlock_irqrestore(&device_domain_lock, flags);
> > --
> > 1.7.9.5


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