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SubjectRe: [PATCH kernel v8 15/31] powerpc/iommu: Fix IOMMU ownership control functions
On Fri, Apr 10, 2015 at 04:30:57PM +1000, Alexey Kardashevskiy wrote:
> This adds missing locks in iommu_take_ownership()/
> iommu_release_ownership().
>
> This marks all pages busy in iommu_table::it_map in order to catch
> errors if there is an attempt to use this table while ownership over it
> is taken.
>
> This only clears TCE content if there is no page marked busy in it_map.
> Clearing must be done outside of the table locks as iommu_clear_tce()
> called from iommu_clear_tces_and_put_pages() does this.
>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
> Changes:
> v5:
> * do not store bit#0 value, it has to be set for zero-based table
> anyway
> * removed test_and_clear_bit
> ---
> arch/powerpc/kernel/iommu.c | 26 ++++++++++++++++++++++----
> 1 file changed, 22 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
> index 7d6089b..068fe4ff 100644
> --- a/arch/powerpc/kernel/iommu.c
> +++ b/arch/powerpc/kernel/iommu.c
> @@ -1052,17 +1052,28 @@ EXPORT_SYMBOL_GPL(iommu_tce_build);
>
> static int iommu_table_take_ownership(struct iommu_table *tbl)
> {
> - unsigned long sz = (tbl->it_size + 7) >> 3;
> + unsigned long flags, i, sz = (tbl->it_size + 7) >> 3;
> + int ret = 0;
> +
> + spin_lock_irqsave(&tbl->large_pool.lock, flags);
> + for (i = 0; i < tbl->nr_pools; i++)
> + spin_lock(&tbl->pools[i].lock);
>
> if (tbl->it_offset == 0)
> clear_bit(0, tbl->it_map);
>
> if (!bitmap_empty(tbl->it_map, tbl->it_size)) {
> pr_err("iommu_tce: it_map is not empty");
> - return -EBUSY;
> + ret = -EBUSY;
> + if (tbl->it_offset == 0)
> + set_bit(0, tbl->it_map);

This really needs a comment. Why on earth are you changing the it_map
on a failure case?

> + } else {
> + memset(tbl->it_map, 0xff, sz);
> }
>
> - memset(tbl->it_map, 0xff, sz);
> + for (i = 0; i < tbl->nr_pools; i++)
> + spin_unlock(&tbl->pools[i].lock);
> + spin_unlock_irqrestore(&tbl->large_pool.lock, flags);
>
> return 0;
> }
> @@ -1095,7 +1106,11 @@ EXPORT_SYMBOL_GPL(iommu_take_ownership);
>
> static void iommu_table_release_ownership(struct iommu_table *tbl)
> {
> - unsigned long sz = (tbl->it_size + 7) >> 3;
> + unsigned long flags, i, sz = (tbl->it_size + 7) >> 3;
> +
> + spin_lock_irqsave(&tbl->large_pool.lock, flags);
> + for (i = 0; i < tbl->nr_pools; i++)
> + spin_lock(&tbl->pools[i].lock);
>
> memset(tbl->it_map, 0, sz);
>
> @@ -1103,6 +1118,9 @@ static void iommu_table_release_ownership(struct iommu_table *tbl)
> if (tbl->it_offset == 0)
> set_bit(0, tbl->it_map);
>
> + for (i = 0; i < tbl->nr_pools; i++)
> + spin_unlock(&tbl->pools[i].lock);
> + spin_unlock_irqrestore(&tbl->large_pool.lock, flags);
> }
>
> extern void iommu_release_ownership(struct iommu_table_group *table_group)

--
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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