On Tue, 2014-09-23 at 13:00 +1000, Alexey Kardashevskiy wrote:
> Modern IBM POWERPC systems support multiple IOMMU tables per PE
> so we need a more reliable way (compared to container_of()) to get
> a PE pointer from the iommu_table struct pointer used in IOMMU functions.
> 
> At the moment IOMMU group data points to an iommu_table struct. This
> introduces a spapr_tce_iommu_group struct which keeps an iommu_owner
> and a spapr_tce_iommu_ops struct. For IODA, iommu_owner is a pointer to
> the pnv_ioda_pe struct, for others it is still a pointer to
> the iommu_table struct. The ops structs correspond to the type which
> iommu_owner points to.
> 
> This defines a get_table() callback which returns an iommu_table
> by its number.
> 
> As the IOMMU group data pointer points to variable type instead of
> iommu_table, VFIO SPAPR TCE driver is updated to use the new type.
> This changes the tce_container struct to store iommu_group instead of
> iommu_table.
> 
> So, it was:
> - iommu_table points to iommu_group via iommu_table::it_group;
> - iommu_group points to iommu_table via iommu_group_get_iommudata();
> 
> now it is:
> - iommu_table points to iommu_group via iommu_table::it_group;
> - iommu_group points to spapr_tce_iommu_group via
> iommu_group_get_iommudata();
> - spapr_tce_iommu_group points to either (depending on .get_table()):
>       - iommu_table;
>       - pnv_ioda_pe;
> 
> This uses pnv_ioda1_iommu_get_table for both IODA1&2 but IODA2 will
> have own pnv_ioda2_iommu_get_table soon and pnv_ioda1_iommu_get_table
> will only be used for IODA1.
> 
> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
> ---
>  arch/powerpc/include/asm/iommu.h            |   6 ++
>  arch/powerpc/include/asm/tce.h              |  13 +++
>  arch/powerpc/kernel/iommu.c                 |  35 ++++++-
>  arch/powerpc/platforms/powernv/pci-ioda.c   |  31 +++++-
>  arch/powerpc/platforms/powernv/pci-p5ioc2.c |   1 +
>  arch/powerpc/platforms/powernv/pci.c        |   2 +-
>  arch/powerpc/platforms/pseries/iommu.c      |  10 +-
>  drivers/vfio/vfio_iommu_spapr_tce.c         | 148 
> ++++++++++++++++++++++------
>  8 files changed, 208 insertions(+), 38 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/iommu.h 
> b/arch/powerpc/include/asm/iommu.h
> index 42632c7..84ee339 100644
> --- a/arch/powerpc/include/asm/iommu.h
> +++ b/arch/powerpc/include/asm/iommu.h
> @@ -108,13 +108,19 @@ extern void iommu_free_table(struct iommu_table *tbl, 
> const char *node_name);
>   */
>  extern struct iommu_table *iommu_init_table(struct iommu_table * tbl,
>                                           int nid);
> +
> +struct spapr_tce_iommu_ops;
>  #ifdef CONFIG_IOMMU_API
>  extern void iommu_register_group(struct iommu_table *tbl,
> +                              void *iommu_owner,
> +                              struct spapr_tce_iommu_ops *ops,
>                                int pci_domain_number, unsigned long pe_num);
>  extern int iommu_add_device(struct device *dev);
>  extern void iommu_del_device(struct device *dev);
>  #else
>  static inline void iommu_register_group(struct iommu_table *tbl,
> +                                     void *iommu_owner,
> +                                     struct spapr_tce_iommu_ops *ops,
>                                       int pci_domain_number,
>                                       unsigned long pe_num)
>  {
> diff --git a/arch/powerpc/include/asm/tce.h b/arch/powerpc/include/asm/tce.h
> index 743f36b..9f159eb 100644
> --- a/arch/powerpc/include/asm/tce.h
> +++ b/arch/powerpc/include/asm/tce.h
> @@ -50,5 +50,18 @@
>  #define TCE_PCI_READ         0x1             /* read from PCI allowed */
>  #define TCE_VB_WRITE         0x1             /* write from VB allowed */
>  
> +struct spapr_tce_iommu_group;
> +
> +struct spapr_tce_iommu_ops {
> +     struct iommu_table *(*get_table)(
> +                     struct spapr_tce_iommu_group *data,
> +                     int num);
> +};
> +
> +struct spapr_tce_iommu_group {
> +     void *iommu_owner;
> +     struct spapr_tce_iommu_ops *ops;
> +};
> +
>  #endif /* __KERNEL__ */
>  #endif /* _ASM_POWERPC_TCE_H */
> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
> index b378f78..1c5dae7 100644
> --- a/arch/powerpc/kernel/iommu.c
> +++ b/arch/powerpc/kernel/iommu.c
> @@ -878,24 +878,53 @@ void iommu_free_coherent(struct iommu_table *tbl, 
> size_t size,
>   */
>  static void group_release(void *iommu_data)
>  {
> -     struct iommu_table *tbl = iommu_data;
> -     tbl->it_group = NULL;
> +     kfree(iommu_data);
>  }
>  
> +static struct iommu_table *spapr_tce_default_get_table(
> +             struct spapr_tce_iommu_group *data, int num)
> +{
> +     struct iommu_table *tbl = data->iommu_owner;
> +
> +     switch (num) {
> +     case 0:
> +             if (tbl->it_size)
> +                     return tbl;
> +             /* fallthru */
> +     default:
> +             return NULL;
> +     }
> +}
> +
> +static struct spapr_tce_iommu_ops spapr_tce_default_ops = {
> +     .get_table = spapr_tce_default_get_table
> +};
> +
>  void iommu_register_group(struct iommu_table *tbl,
> +             void *iommu_owner, struct spapr_tce_iommu_ops *ops,
>               int pci_domain_number, unsigned long pe_num)
>  {
>       struct iommu_group *grp;
>       char *name;
> +     struct spapr_tce_iommu_group *data;
> +
> +     data = kzalloc(sizeof(*data), GFP_KERNEL);
> +     if (!data)
> +             return;
> +
> +     data->iommu_owner = iommu_owner ? iommu_owner : tbl;
> +     data->ops = ops ? ops : &spapr_tce_default_ops;
>  
>       grp = iommu_group_alloc();
>       if (IS_ERR(grp)) {
>               pr_warn("powerpc iommu api: cannot create new group, err=%ld\n",
>                               PTR_ERR(grp));
> +             kfree(data);
>               return;
>       }
> +
>       tbl->it_group = grp;
> -     iommu_group_set_iommudata(grp, tbl, group_release);
> +     iommu_group_set_iommudata(grp, data, group_release);
>       name = kasprintf(GFP_KERNEL, "domain%d-pe%lx",
>                       pci_domain_number, pe_num);
>       if (!name)
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c 
> b/arch/powerpc/platforms/powernv/pci-ioda.c
> index 136e765..2d32a1c 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -23,6 +23,7 @@
>  #include <linux/io.h>
>  #include <linux/msi.h>
>  #include <linux/memblock.h>
> +#include <linux/iommu.h>
>  
>  #include <asm/sections.h>
>  #include <asm/io.h>
> @@ -988,6 +989,26 @@ static void pnv_pci_ioda2_tce_invalidate(struct 
> pnv_ioda_pe *pe,
>       }
>  }
>  
> +static struct iommu_table *pnv_ioda1_iommu_get_table(
> +             struct spapr_tce_iommu_group *data,
> +             int num)
> +{
> +     struct pnv_ioda_pe *pe = data->iommu_owner;
> +
> +     switch (num) {
> +     case 0:
> +             if (pe->tce32.table.it_size)
> +                     return &pe->tce32.table;
> +             /* fallthru */
> +     default:
> +             return NULL;
> +     }
> +}
> +
> +static struct spapr_tce_iommu_ops pnv_pci_ioda1_ops = {
> +     .get_table = pnv_ioda1_iommu_get_table,
> +};
> +
>  static void pnv_pci_ioda_setup_dma_pe(struct pnv_phb *phb,
>                                     struct pnv_ioda_pe *pe, unsigned int base,
>                                     unsigned int segs)
> @@ -1067,7 +1088,8 @@ static void pnv_pci_ioda_setup_dma_pe(struct pnv_phb 
> *phb,
>                                TCE_PCI_SWINV_PAIR);
>       }
>       iommu_init_table(tbl, phb->hose->node);
> -     iommu_register_group(tbl, phb->hose->global_number, pe->pe_number);
> +     iommu_register_group(tbl, pe, &pnv_pci_ioda1_ops,
> +                     phb->hose->global_number, pe->pe_number);
>  
>       if (pe->pdev)
>               set_iommu_table_base_and_group(&pe->pdev->dev, tbl);
> @@ -1137,6 +1159,10 @@ static void pnv_pci_ioda2_setup_bypass_pe(struct 
> pnv_phb *phb,
>       pnv_pci_ioda2_set_bypass(&pe->tce32.table, true);
>  }
>  
> +static struct spapr_tce_iommu_ops pnv_pci_ioda2_ops = {
> +     .get_table = pnv_ioda1_iommu_get_table,
> +};
> +
>  static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
>                                      struct pnv_ioda_pe *pe)
>  {
> @@ -1202,7 +1228,8 @@ static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb 
> *phb,
>               tbl->it_type |= (TCE_PCI_SWINV_CREATE | TCE_PCI_SWINV_FREE);
>       }
>       iommu_init_table(tbl, phb->hose->node);
> -     iommu_register_group(tbl, phb->hose->global_number, pe->pe_number);
> +     iommu_register_group(tbl, pe, &pnv_pci_ioda2_ops,
> +                     phb->hose->global_number, pe->pe_number);
>  
>       if (pe->pdev)
>               set_iommu_table_base_and_group(&pe->pdev->dev, tbl);
> diff --git a/arch/powerpc/platforms/powernv/pci-p5ioc2.c 
> b/arch/powerpc/platforms/powernv/pci-p5ioc2.c
> index 94ce348..b79066d 100644
> --- a/arch/powerpc/platforms/powernv/pci-p5ioc2.c
> +++ b/arch/powerpc/platforms/powernv/pci-p5ioc2.c
> @@ -89,6 +89,7 @@ static void pnv_pci_p5ioc2_dma_dev_setup(struct pnv_phb 
> *phb,
>       if (phb->p5ioc2.iommu_table.it_map == NULL) {
>               iommu_init_table(&phb->p5ioc2.iommu_table, phb->hose->node);
>               iommu_register_group(&phb->p5ioc2.iommu_table,
> +                             NULL, NULL,
>                               pci_domain_nr(phb->hose->bus), phb->opal_id);
>       }
>  
> diff --git a/arch/powerpc/platforms/powernv/pci.c 
> b/arch/powerpc/platforms/powernv/pci.c
> index 97895d4..6ffac79 100644
> --- a/arch/powerpc/platforms/powernv/pci.c
> +++ b/arch/powerpc/platforms/powernv/pci.c
> @@ -723,7 +723,7 @@ static struct iommu_table *pnv_pci_setup_bml_iommu(struct 
> pci_controller *hose)
>       pnv_pci_setup_iommu_table(tbl, __va(be64_to_cpup(basep)),
>                                 be32_to_cpup(sizep), 0, IOMMU_PAGE_SHIFT_4K);
>       iommu_init_table(tbl, hose->node);
> -     iommu_register_group(tbl, pci_domain_nr(hose->bus), 0);
> +     iommu_register_group(tbl, NULL, NULL, pci_domain_nr(hose->bus), 0);
>  
>       /* Deal with SW invalidated TCEs when needed (BML way) */
>       swinvp = of_get_property(hose->dn, "linux,tce-sw-invalidate-info",
> diff --git a/arch/powerpc/platforms/pseries/iommu.c 
> b/arch/powerpc/platforms/pseries/iommu.c
> index 4642d6a..b95f8cf 100644
> --- a/arch/powerpc/platforms/pseries/iommu.c
> +++ b/arch/powerpc/platforms/pseries/iommu.c
> @@ -616,7 +616,7 @@ static void pci_dma_bus_setup_pSeries(struct pci_bus *bus)
>  
>       iommu_table_setparms(pci->phb, dn, tbl);
>       pci->iommu_table = iommu_init_table(tbl, pci->phb->node);
> -     iommu_register_group(tbl, pci_domain_nr(bus), 0);
> +     iommu_register_group(tbl, NULL, NULL, pci_domain_nr(bus), 0);
>  
>       /* Divide the rest (1.75GB) among the children */
>       pci->phb->dma_window_size = 0x80000000ul;
> @@ -661,7 +661,7 @@ static void pci_dma_bus_setup_pSeriesLP(struct pci_bus 
> *bus)
>                                  ppci->phb->node);
>               iommu_table_setparms_lpar(ppci->phb, pdn, tbl, dma_window);
>               ppci->iommu_table = iommu_init_table(tbl, ppci->phb->node);
> -             iommu_register_group(tbl, pci_domain_nr(bus), 0);
> +             iommu_register_group(tbl, NULL, NULL, pci_domain_nr(bus), 0);
>               pr_debug("  created table: %p\n", ppci->iommu_table);
>       }
>  }
> @@ -688,7 +688,8 @@ static void pci_dma_dev_setup_pSeries(struct pci_dev *dev)
>                                  phb->node);
>               iommu_table_setparms(phb, dn, tbl);
>               PCI_DN(dn)->iommu_table = iommu_init_table(tbl, phb->node);
> -             iommu_register_group(tbl, pci_domain_nr(phb->bus), 0);
> +             iommu_register_group(tbl, NULL, NULL,
> +                             pci_domain_nr(phb->bus), 0);
>               set_iommu_table_base_and_group(&dev->dev,
>                                              PCI_DN(dn)->iommu_table);
>               return;
> @@ -1105,7 +1106,8 @@ static void pci_dma_dev_setup_pSeriesLP(struct pci_dev 
> *dev)
>                                  pci->phb->node);
>               iommu_table_setparms_lpar(pci->phb, pdn, tbl, dma_window);
>               pci->iommu_table = iommu_init_table(tbl, pci->phb->node);
> -             iommu_register_group(tbl, pci_domain_nr(pci->phb->bus), 0);
> +             iommu_register_group(tbl, NULL, NULL,
> +                             pci_domain_nr(pci->phb->bus), 0);
>               pr_debug("  created table: %p\n", pci->iommu_table);
>       } else {
>               pr_debug("  found DMA window, table: %p\n", pci->iommu_table);
> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c 
> b/drivers/vfio/vfio_iommu_spapr_tce.c
> index 730b4ef..a8adfbd 100644
> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> @@ -43,17 +43,51 @@ static void tce_iommu_detach_group(void *iommu_data,
>   */
>  struct tce_container {
>       struct mutex lock;
> -     struct iommu_table *tbl;
> +     struct iommu_group *grp;
> +     long windows_num;
>       bool enabled;
>  };
>  
> +static struct iommu_table *spapr_tce_find_table(
> +             struct tce_container *container,
> +             struct spapr_tce_iommu_group *data,
> +             phys_addr_t ioba)
> +{
> +     long i;
> +     struct iommu_table *ret = NULL;
> +
> +     mutex_lock(&container->lock);
> +     for (i = 0; i < container->windows_num; ++i) {
> +             struct iommu_table *tbl = data->ops->get_table(data, i);
> +
> +             if (tbl) {
> +                     unsigned long entry = ioba >> tbl->it_page_shift;
> +                     unsigned long start = tbl->it_offset;
> +                     unsigned long end = start + tbl->it_size;
> +
> +                     if ((start <= entry) && (entry < end)) {
> +                             ret = tbl;
> +                             break;
> +                     }
> +             }
> +     }
> +     mutex_unlock(&container->lock);
> +
> +     return ret;
> +}
> +
>  static int tce_iommu_enable(struct tce_container *container)
>  {
>       int ret = 0;
>       unsigned long locked, lock_limit, npages;
> -     struct iommu_table *tbl = container->tbl;
> +     struct iommu_table *tbl;
> +     struct spapr_tce_iommu_group *data;
>  
> -     if (!container->tbl)
> +     if (!container->grp)
> +             return -ENXIO;
> +
> +     data = iommu_group_get_iommudata(container->grp);
> +     if (!data || !data->iommu_owner || !data->ops->get_table)
>               return -ENXIO;
>  
>       if (!current->mm)
> @@ -80,6 +114,10 @@ static int tce_iommu_enable(struct tce_container 
> *container)
>        * that would effectively kill the guest at random points, much better
>        * enforcing the limit based on the max that the guest can map.
>        */
> +     tbl = data->ops->get_table(data, 0);

Can we define an enum to avoid sprinkling magic zeros in the code?

> +     if (!tbl)
> +             return -ENXIO;
> +
>       down_write(&current->mm->mmap_sem);
>       npages = (tbl->it_size << IOMMU_PAGE_SHIFT_4K) >> PAGE_SHIFT;
>       locked = current->mm->locked_vm + npages;
> @@ -89,7 +127,6 @@ static int tce_iommu_enable(struct tce_container 
> *container)
>                               rlimit(RLIMIT_MEMLOCK));
>               ret = -ENOMEM;
>       } else {
> -
>               current->mm->locked_vm += npages;
>               container->enabled = true;
>       }
> @@ -100,16 +137,27 @@ static int tce_iommu_enable(struct tce_container 
> *container)
>  
>  static void tce_iommu_disable(struct tce_container *container)
>  {
> +     struct spapr_tce_iommu_group *data;
> +     struct iommu_table *tbl;
> +
>       if (!container->enabled)
>               return;
>  
>       container->enabled = false;
>  
> -     if (!container->tbl || !current->mm)
> +     if (!container->grp || !current->mm)
> +             return;
> +
> +     data = iommu_group_get_iommudata(container->grp);
> +     if (!data || !data->iommu_owner || !data->ops->get_table)
> +             return;
> +
> +     tbl = data->ops->get_table(data, 0);
> +     if (!tbl)
>               return;
>  
>       down_write(&current->mm->mmap_sem);
> -     current->mm->locked_vm -= (container->tbl->it_size <<
> +     current->mm->locked_vm -= (tbl->it_size <<
>                       IOMMU_PAGE_SHIFT_4K) >> PAGE_SHIFT;
>       up_write(&current->mm->mmap_sem);
>  }
> @@ -129,6 +177,8 @@ static void *tce_iommu_open(unsigned long arg)
>  
>       mutex_init(&container->lock);
>  
> +     container->windows_num = 1;
> +
>       return container;
>  }
>  
> @@ -136,11 +186,11 @@ static void tce_iommu_release(void *iommu_data)
>  {
>       struct tce_container *container = iommu_data;
>  
> -     WARN_ON(container->tbl && !container->tbl->it_group);
> +     WARN_ON(container->grp);
>       tce_iommu_disable(container);
>  
> -     if (container->tbl && container->tbl->it_group)
> -             tce_iommu_detach_group(iommu_data, container->tbl->it_group);
> +     if (container->grp)
> +             tce_iommu_detach_group(iommu_data, container->grp);
>  
>       mutex_destroy(&container->lock);
>  
> @@ -169,8 +219,17 @@ static long tce_iommu_ioctl(void *iommu_data,
>  
>       case VFIO_IOMMU_SPAPR_TCE_GET_INFO: {
>               struct vfio_iommu_spapr_tce_info info;
> -             struct iommu_table *tbl = container->tbl;
> +             struct iommu_table *tbl;
> +             struct spapr_tce_iommu_group *data;
>  
> +             if (WARN_ON(!container->grp))
> +                     return -ENXIO;
> +
> +             data = iommu_group_get_iommudata(container->grp);
> +             if (WARN_ON(!data || !data->iommu_owner || !data->ops))
> +                     return -ENXIO;
> +
> +             tbl = data->ops->get_table(data, 0);
>               if (WARN_ON(!tbl))
>                       return -ENXIO;
>  
> @@ -194,13 +253,16 @@ static long tce_iommu_ioctl(void *iommu_data,
>       }
>       case VFIO_IOMMU_MAP_DMA: {
>               struct vfio_iommu_type1_dma_map param;
> -             struct iommu_table *tbl = container->tbl;
> +             struct iommu_table *tbl;
> +             struct spapr_tce_iommu_group *data;
>               unsigned long tce, i;
>  
> -             if (!tbl)
> +             if (WARN_ON(!container->grp))

If a user can get here by their own mistake, return an error and be
done, no warning.  If a user can get here via a kernel ordering issue,
it's a problem in the design.  Which is it?

>                       return -ENXIO;
>  
> -             BUG_ON(!tbl->it_group);
> +             data = iommu_group_get_iommudata(container->grp);
> +             if (WARN_ON(!data || !data->iommu_owner || !data->ops))
> +                     return -ENXIO;

Same

>  
>               minsz = offsetofend(struct vfio_iommu_type1_dma_map, size);
>  
> @@ -225,6 +287,11 @@ static long tce_iommu_ioctl(void *iommu_data,
>               if (param.flags & VFIO_DMA_MAP_FLAG_WRITE)
>                       tce |= TCE_PCI_WRITE;
>  
> +             tbl = spapr_tce_find_table(container, data, param.iova);

Why aren't we using ops->find_table() here?

> +             if (!tbl)
> +                     return -ENXIO;
> +             BUG_ON(!tbl->it_group);
> +
>               ret = iommu_tce_put_param_check(tbl, param.iova, tce);
>               if (ret)
>                       return ret;
> @@ -247,9 +314,14 @@ static long tce_iommu_ioctl(void *iommu_data,
>       }
>       case VFIO_IOMMU_UNMAP_DMA: {
>               struct vfio_iommu_type1_dma_unmap param;
> -             struct iommu_table *tbl = container->tbl;
> +             struct iommu_table *tbl;
> +             struct spapr_tce_iommu_group *data;
>  
> -             if (WARN_ON(!tbl))
> +             if (WARN_ON(!container->grp))
> +                     return -ENXIO;
> +
> +             data = iommu_group_get_iommudata(container->grp);
> +             if (WARN_ON(!data || !data->iommu_owner || !data->ops))
>                       return -ENXIO;

Same as above on both of these.

>  
>               minsz = offsetofend(struct vfio_iommu_type1_dma_unmap,
> @@ -268,6 +340,12 @@ static long tce_iommu_ioctl(void *iommu_data,
>               if (param.size & ~IOMMU_PAGE_MASK_4K)
>                       return -EINVAL;
>  
> +             tbl = spapr_tce_find_table(container, data, param.iova);

ops->find_table()?

> +             if (!tbl)
> +                     return -ENXIO;
> +
> +             BUG_ON(!tbl->it_group);
> +
>               ret = iommu_tce_clear_param_check(tbl, param.iova, 0,
>                               param.size >> IOMMU_PAGE_SHIFT_4K);
>               if (ret)
> @@ -293,10 +371,10 @@ static long tce_iommu_ioctl(void *iommu_data,
>               mutex_unlock(&container->lock);
>               return 0;
>       case VFIO_EEH_PE_OP:
> -             if (!container->tbl || !container->tbl->it_group)
> +             if (!container->grp)
>                       return -ENODEV;
>  
> -             return vfio_spapr_iommu_eeh_ioctl(container->tbl->it_group,
> +             return vfio_spapr_iommu_eeh_ioctl(container->grp,
>                                                 cmd, arg);
>       }
>  
> @@ -308,16 +386,16 @@ static int tce_iommu_attach_group(void *iommu_data,
>  {
>       int ret;
>       struct tce_container *container = iommu_data;
> -     struct iommu_table *tbl = iommu_group_get_iommudata(iommu_group);
> +     struct iommu_table *tbl;
> +     struct spapr_tce_iommu_group *data;
>  
> -     BUG_ON(!tbl);
>       mutex_lock(&container->lock);
>  
>       /* pr_debug("tce_vfio: Attaching group #%u to iommu %p\n",
>                       iommu_group_id(iommu_group), iommu_group); */
> -     if (container->tbl) {
> +     if (container->grp) {
>               pr_warn("tce_vfio: Only one group per IOMMU container is 
> allowed, existing id=%d, attaching id=%d\n",
> -                             iommu_group_id(container->tbl->it_group),
> +                             iommu_group_id(container->grp),
>                               iommu_group_id(iommu_group));
>               ret = -EBUSY;
>       } else if (container->enabled) {
> @@ -325,9 +403,16 @@ static int tce_iommu_attach_group(void *iommu_data,
>                               iommu_group_id(iommu_group));
>               ret = -EBUSY;
>       } else {
> +             data = iommu_group_get_iommudata(iommu_group);
> +             if (WARN_ON(!data || !data->iommu_owner || !data->ops))
> +                     return -ENXIO;
> +
> +             tbl = data->ops->get_table(data, 0);
> +             BUG_ON(!tbl);

Why BUG_ON?  A user can attempt to attach any group to any container, do
you really want to give them the ability to halt the system?

> +
>               ret = iommu_take_ownership(tbl);
>               if (!ret)
> -                     container->tbl = tbl;
> +                     container->grp = iommu_group;
>       }
>  
>       mutex_unlock(&container->lock);
> @@ -339,24 +424,31 @@ static void tce_iommu_detach_group(void *iommu_data,
>               struct iommu_group *iommu_group)
>  {
>       struct tce_container *container = iommu_data;
> -     struct iommu_table *tbl = iommu_group_get_iommudata(iommu_group);
> +     struct iommu_table *tbl;
> +     struct spapr_tce_iommu_group *data;
>  
> -     BUG_ON(!tbl);
>       mutex_lock(&container->lock);
> -     if (tbl != container->tbl) {
> +     if (iommu_group != container->grp) {
>               pr_warn("tce_vfio: detaching group #%u, expected group is 
> #%u\n",
>                               iommu_group_id(iommu_group),
> -                             iommu_group_id(tbl->it_group));
> +                             iommu_group_id(container->grp));
>       } else {
>               if (container->enabled) {
>                       pr_warn("tce_vfio: detaching group #%u from enabled 
> container, forcing disable\n",
> -                                     iommu_group_id(tbl->it_group));
> +                                     iommu_group_id(container->grp));
>                       tce_iommu_disable(container);
>               }
>  
>               /* pr_debug("tce_vfio: detaching group #%u from iommu %p\n",
>                               iommu_group_id(iommu_group), iommu_group); */
> -             container->tbl = NULL;
> +             container->grp = NULL;
> +
> +             data = iommu_group_get_iommudata(iommu_group);
> +             BUG_ON(!data || !data->iommu_owner || !data->ops);
> +
> +             tbl = data->ops->get_table(data, 0);
> +             BUG_ON(!tbl);
> +
>               iommu_release_ownership(tbl);
>       }
>       mutex_unlock(&container->lock);

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