Re: [PATCH kernel v9 26/32] powerpc/iommu: Add userspace view of TCE table

David Gibson
2015-04-29T22:33:56Z

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On Sat, Apr 25, 2015 at 10:14:50PM +1000, Alexey Kardashevskiy wrote:
> In order to support memory pre-registration, we need a way to track
> the use of every registered memory region and only allow unregistration
> if a region is not in use anymore. So we need a way to tell from what
> region the just cleared TCE was from.
>
> This adds a userspace view of the TCE table into iommu_table struct.
> It contains userspace address, one per TCE entry. The table is only
> allocated when the ownership over an IOMMU group is taken which means
> it is only used from outside of the powernv code (such as VFIO).
>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
> Changes:
> v9:
> * fixed code flow in error cases added in v8
>
> v8:
> * added ENOMEM on failed vzalloc()
> ---
> arch/powerpc/include/asm/iommu.h | 6 ++++++
> arch/powerpc/kernel/iommu.c | 18 ++++++++++++++++++
> arch/powerpc/platforms/powernv/pci-ioda.c | 22 ++++++++++++++++++++--
> 3 files changed, 44 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
> index 7694546..1472de3 100644
> --- a/arch/powerpc/include/asm/iommu.h
> +++ b/arch/powerpc/include/asm/iommu.h
> @@ -111,9 +111,15 @@ struct iommu_table {
> unsigned long *it_map; /* A simple allocation bitmap for now */
> unsigned long it_page_shift;/* table iommu page size */
> struct iommu_table_group *it_table_group;
> + unsigned long *it_userspace; /* userspace view of the table */

A single unsigned long doesn't seem like enough. How do you know
which process's address space this address refers to?

> struct iommu_table_ops *it_ops;
> };
>
> +#define IOMMU_TABLE_USERSPACE_ENTRY(tbl, entry) \
> + ((tbl)->it_userspace ? \
> + &((tbl)->it_userspace[(entry) - (tbl)->it_offset]) : \
> + NULL)
> +
> /* Pure 2^n version of get_order */
> static inline __attribute_const__
> int get_iommu_order(unsigned long size, struct iommu_table *tbl)
> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
> index 2eaba0c..74a3f52 100644
> --- a/arch/powerpc/kernel/iommu.c
> +++ b/arch/powerpc/kernel/iommu.c
> @@ -38,6 +38,7 @@
> #include <linux/pci.h>
> #include <linux/iommu.h>
> #include <linux/sched.h>
> +#include <linux/vmalloc.h>
> #include <asm/io.h>
> #include <asm/prom.h>
> #include <asm/iommu.h>
> @@ -739,6 +740,8 @@ void iommu_reset_table(struct iommu_table *tbl, const char *node_name)
> free_pages((unsigned long) tbl->it_map, order);
> }
>
> + WARN_ON(tbl->it_userspace);
> +
> memset(tbl, 0, sizeof(*tbl));
> }
>
> @@ -1016,6 +1019,7 @@ int iommu_take_ownership(struct iommu_table *tbl)
> {
> unsigned long flags, i, sz = (tbl->it_size + 7) >> 3;
> int ret = 0;
> + unsigned long *uas;
>
> /*
> * VFIO does not control TCE entries allocation and the guest
> @@ -1027,6 +1031,10 @@ int iommu_take_ownership(struct iommu_table *tbl)
> if (!tbl->it_ops->exchange)
> return -EINVAL;
>
> + uas = vzalloc(sizeof(*uas) * tbl->it_size);
> + if (!uas)
> + return -ENOMEM;
> +
> spin_lock_irqsave(&tbl->large_pool.lock, flags);
> for (i = 0; i < tbl->nr_pools; i++)
> spin_lock(&tbl->pools[i].lock);
> @@ -1044,6 +1052,13 @@ int iommu_take_ownership(struct iommu_table *tbl)
> memset(tbl->it_map, 0xff, sz);
> }
>
> + if (ret) {
> + vfree(uas);
> + } else {
> + BUG_ON(tbl->it_userspace);
> + tbl->it_userspace = uas;
> + }
> +
> for (i = 0; i < tbl->nr_pools; i++)
> spin_unlock(&tbl->pools[i].lock);
> spin_unlock_irqrestore(&tbl->large_pool.lock, flags);
> @@ -1056,6 +1071,9 @@ void iommu_release_ownership(struct iommu_table *tbl)
> {
> unsigned long flags, i, sz = (tbl->it_size + 7) >> 3;
>
> + vfree(tbl->it_userspace);
> + tbl->it_userspace = NULL;
> +
> spin_lock_irqsave(&tbl->large_pool.lock, flags);
> for (i = 0; i < tbl->nr_pools; i++)
> spin_lock(&tbl->pools[i].lock);
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
> index 45bc131..e0be556 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -25,6 +25,7 @@
> #include <linux/memblock.h>
> #include <linux/iommu.h>
> #include <linux/sizes.h>
> +#include <linux/vmalloc.h>
>
> #include <asm/sections.h>
> #include <asm/io.h>
> @@ -1827,6 +1828,14 @@ static void pnv_ioda2_tce_free(struct iommu_table *tbl, long index,
> pnv_pci_ioda2_tce_invalidate(tbl, index, npages, false);
> }
>
> +void pnv_pci_ioda2_free_table(struct iommu_table *tbl)
> +{
> + vfree(tbl->it_userspace);
> + tbl->it_userspace = NULL;
> +
> + pnv_pci_free_table(tbl);
> +}
> +
> static struct iommu_table_ops pnv_ioda2_iommu_ops = {
> .set = pnv_ioda2_tce_build,
> #ifdef CONFIG_IOMMU_API
> @@ -1834,7 +1843,7 @@ static struct iommu_table_ops pnv_ioda2_iommu_ops = {
> #endif
> .clear = pnv_ioda2_tce_free,
> .get = pnv_tce_get,
> - .free = pnv_pci_free_table,
> + .free = pnv_pci_ioda2_free_table,
> };
>
> static void pnv_pci_ioda_setup_opal_tce_kill(struct pnv_phb *phb,
> @@ -2062,12 +2071,21 @@ static long pnv_pci_ioda2_create_table(struct iommu_table_group *table_group,
> int nid = pe->phb->hose->node;
> __u64 bus_offset = num ? pe->tce_bypass_base : 0;
> long ret;
> + unsigned long *uas, uas_cb = sizeof(*uas) * (window_size >> page_shift);
> +
> + uas = vzalloc(uas_cb);
> + if (!uas)
> + return -ENOMEM;

I don't see why this is allocated both here as well as in
take_ownership. Isn't this function used for core-kernel users of the
iommu as well, in which case it shouldn't need the it_userspace.

> ret = pnv_pci_create_table(table_group, nid, bus_offset, page_shift,
> window_size, levels, tbl);
> - if (ret)
> + if (ret) {
> + vfree(uas);
> return ret;
> + }
>
> + BUG_ON(tbl->it_userspace);
> + tbl->it_userspace = uas;
> tbl->it_ops = &pnv_ioda2_iommu_ops;
> if (pe->tce_inval_reg)
> tbl->it_type |= (TCE_PCI_SWINV_CREATE | TCE_PCI_SWINV_FREE);

--
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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