Re: [PATCH kernel v9 13/32] vfio: powerpc/spapr/iommu/powernv/ioda2: Rework IOMMU ownership control

David Gibson
2015-04-29T03:27:31Z

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On Sat, Apr 25, 2015 at 10:14:37PM +1000, Alexey Kardashevskiy wrote:
> This adds tce_iommu_take_ownership() and tce_iommu_release_ownership
> which call in a loop iommu_take_ownership()/iommu_release_ownership()
> for every table on the group. As there is just one now, no change in
> behaviour is expected.
>
> 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.
>
> The set_bypass() callback is not really an iommu_table function but
> IOMMU/PE function. This introduces a iommu_table_group_ops struct and
> adds take_ownership()/release_ownership() callbacks to it which are
> called when an external user takes/releases control over the IOMMU.
>
> This replaces set_bypass() with ownership callbacks as it is not
> necessarily just bypass enabling, it can be something else/more
> so let's give it more generic name.
>
> The callbacks is implemented for IODA2 only. Other platforms (P5IOC2,
> IODA1) will use the old iommu_take_ownership/iommu_release_ownership API.
> The following patches will replace iommu_take_ownership/
> iommu_release_ownership calls in IODA2 with full IOMMU table release/
> create.
>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> [aw: for the vfio related changes]
> Acked-by: Alex Williamson <alex.williamson@redhat.com>
> ---
> Changes:
> v9:
> * squashed "vfio: powerpc/spapr: powerpc/iommu: Rework IOMMU ownership control"
> and "vfio: powerpc/spapr: powerpc/powernv/ioda2: Rework IOMMU ownership control"
> into a single patch
> * moved helpers with a loop through tables in a group
> to vfio_iommu_spapr_tce.c to keep the platform code free of IOMMU table
> groups as much as possible
> * added missing tce_iommu_clear() to tce_iommu_release_ownership()
> * replaced the set_ownership(enable) callback with take_ownership() and
> release_ownership()
> ---
> arch/powerpc/include/asm/iommu.h | 13 +++++-
> arch/powerpc/kernel/iommu.c | 11 ------
> arch/powerpc/platforms/powernv/pci-ioda.c | 40 +++++++++++++++----
> drivers/vfio/vfio_iommu_spapr_tce.c | 66 +++++++++++++++++++++++++++----
> 4 files changed, 103 insertions(+), 27 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
> index fa37519..e63419e 100644
> --- a/arch/powerpc/include/asm/iommu.h
> +++ b/arch/powerpc/include/asm/iommu.h
> @@ -93,7 +93,6 @@ struct iommu_table {
> unsigned long it_page_shift;/* table iommu page size */
> struct iommu_table_group *it_table_group;
> struct iommu_table_ops *it_ops;
> - void (*set_bypass)(struct iommu_table *tbl, bool enable);
> };
>
> /* Pure 2^n version of get_order */
> @@ -128,11 +127,23 @@ extern struct iommu_table *iommu_init_table(struct iommu_table * tbl,
>
> #define IOMMU_TABLE_GROUP_MAX_TABLES 1
>
> +struct iommu_table_group;
> +
> +struct iommu_table_group_ops {
> + /*
> + * Switches ownership from the kernel itself to an external
> + * user. While onwership is taken, the kernel cannot use IOMMU itself.

Typo in "onwership". I'd also like to see this be even more explicit
that "take" is the "core kernel -> vfio/whatever" transition and
release is the reverse.

> + */
> + void (*take_ownership)(struct iommu_table_group *table_group);
> + void (*release_ownership)(struct iommu_table_group *table_group);
> +};
> +
> struct iommu_table_group {
> #ifdef CONFIG_IOMMU_API
> struct iommu_group *group;
> #endif
> struct iommu_table tables[IOMMU_TABLE_GROUP_MAX_TABLES];
> + struct iommu_table_group_ops *ops;
> };
>
> #ifdef CONFIG_IOMMU_API
> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
> index 005146b..2856d27 100644
> --- a/arch/powerpc/kernel/iommu.c
> +++ b/arch/powerpc/kernel/iommu.c
> @@ -1057,13 +1057,6 @@ int iommu_take_ownership(struct iommu_table *tbl)
>
> memset(tbl->it_map, 0xff, sz);
>
> - /*
> - * 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;
> }
> @@ -1078,10 +1071,6 @@ 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 88472cb..718d5cc 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -1870,10 +1870,8 @@ 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->it_table_group,
> - struct pnv_ioda_pe, table_group);
> uint16_t window_id = (pe->pe_number << 1 ) + 1;
> int64_t rc;
>
> @@ -1901,7 +1899,8 @@ 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->table_group.tables[0]);
> else
> pnv_ioda_setup_bus_dma(pe, pe->pbus, false);
> }
> @@ -1917,13 +1916,35 @@ 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->table_group.tables[0].set_bypass = pnv_pci_ioda2_set_bypass;
> -
> /* Enable bypass by default */
> - pnv_pci_ioda2_set_bypass(&pe->table_group.tables[0], true);
> + pnv_pci_ioda2_set_bypass(pe, true);
> }
>
> +#ifdef CONFIG_IOMMU_API
> +static void pnv_ioda2_take_ownership(struct iommu_table_group *table_group)
> +{
> + struct pnv_ioda_pe *pe = container_of(table_group, struct pnv_ioda_pe,
> + table_group);
> +
> + iommu_take_ownership(&table_group->tables[0]);
> + pnv_pci_ioda2_set_bypass(pe, false);
> +}
> +
> +static void pnv_ioda2_release_ownership(struct iommu_table_group *table_group)
> +{
> + struct pnv_ioda_pe *pe = container_of(table_group, struct pnv_ioda_pe,
> + table_group);
> +
> + iommu_release_ownership(&table_group->tables[0]);
> + pnv_pci_ioda2_set_bypass(pe, true);
> +}
> +
> +static struct iommu_table_group_ops pnv_pci_ioda2_ops = {
> + .take_ownership = pnv_ioda2_take_ownership,
> + .release_ownership = pnv_ioda2_release_ownership,
> +};
> +#endif
> +
> static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
> struct pnv_ioda_pe *pe)
> {
> @@ -1991,6 +2012,9 @@ static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
> }
> tbl->it_ops = &pnv_ioda2_iommu_ops;
> iommu_init_table(tbl, phb->hose->node);
> +#ifdef CONFIG_IOMMU_API
> + pe->table_group.ops = &pnv_pci_ioda2_ops;
> +#endif
>
> if (pe->flags & PNV_IODA_PE_DEV) {
> iommu_register_group(&pe->table_group, phb->hose->global_number,
> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> index 17e884a..dacc738 100644
> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> @@ -483,6 +483,43 @@ static long tce_iommu_ioctl(void *iommu_data,
> return -ENOTTY;
> }
>
> +static void tce_iommu_release_ownership(struct tce_container *container,
> + struct iommu_table_group *table_group)
> +{
> + int i;
> +
> + for (i = 0; i < IOMMU_TABLE_GROUP_MAX_TABLES; ++i) {
> + struct iommu_table *tbl = &table_group->tables[i];
> +
> + tce_iommu_clear(container, tbl, tbl->it_offset, tbl->it_size);
> + if (tbl->it_map)
> + iommu_release_ownership(tbl);
> + }
> +}
> +
> +static int tce_iommu_take_ownership(struct iommu_table_group *table_group)
> +{
> + int i, j, rc = 0;
> +
> + for (i = 0; i < IOMMU_TABLE_GROUP_MAX_TABLES; ++i) {
> + struct iommu_table *tbl = &table_group->tables[i];
> +
> + if (!tbl->it_map)
> + continue;
> +
> + rc = iommu_take_ownership(tbl);
> + if (rc) {
> + for (j = 0; j < i; ++j)
> + iommu_release_ownership(
> + &table_group->tables[j]);
> +
> + return rc;
> + }
> + }
> +
> + return 0;
> +}
> +
> static int tce_iommu_attach_group(void *iommu_data,
> struct iommu_group *iommu_group)
> {
> @@ -515,9 +552,23 @@ static int tce_iommu_attach_group(void *iommu_data,
> goto unlock_exit;
> }
>
> - ret = iommu_take_ownership(&table_group->tables[0]);
> - if (!ret)
> - container->grp = iommu_group;
> + if (!table_group->ops || !table_group->ops->take_ownership ||
> + !table_group->ops->release_ownership) {
> + ret = tce_iommu_take_ownership(table_group);

Haven't looked at the rest of the series. I'm hoping that you're
eventually planning to replace this fallback with setting the
take_ownership call for p5ioc etc. to point to
tce_iommu_take_ownership.

> + } else {
> + /*
> + * 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
> + */
> + table_group->ops->take_ownership(table_group);
> + ret = 0;
> + }
> +
> + if (ret)
> + goto unlock_exit;
> +
> + container->grp = iommu_group;
>
> unlock_exit:
> mutex_unlock(&container->lock);
> @@ -530,7 +581,6 @@ static void tce_iommu_detach_group(void *iommu_data,
> {
> struct tce_container *container = iommu_data;
> struct iommu_table_group *table_group;
> - struct iommu_table *tbl;
>
> mutex_lock(&container->lock);
> if (iommu_group != container->grp) {
> @@ -553,9 +603,11 @@ static void tce_iommu_detach_group(void *iommu_data,
> table_group = iommu_group_get_iommudata(iommu_group);
> BUG_ON(!table_group);
>
> - tbl = &table_group->tables[0];
> - tce_iommu_clear(container, tbl, tbl->it_offset, tbl->it_size);
> - iommu_release_ownership(tbl);
> + /* Kernel owns the device now, we can restore bypass */
> + if (!table_group->ops || !table_group->ops->release_ownership)
> + tce_iommu_release_ownership(container, table_group);
> + else
> + table_group->ops->release_ownership(table_group);
>
> unlock_exit:
> mutex_unlock(&container->lock);

--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson

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