2013-06-26 05:39:37

by Alexey Kardashevskiy

Subject: [PATCH] powerpc/vfio: Add missing locks for take/release TCE table ownership

VFIO IOMMU driver for sPAPR TCE locks the whole DMA window by setting
ones to iommu_table.it_map. However this was not protected by the locks
which other clients of iommu_table use.

The patch fixes this.

Signed-off-by: Alexey Kardashevskiy <[email protected]>
---
arch/powerpc/kernel/iommu.c | 25 +++++++++++++++++++++++--
1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index b20ff17..9f34742 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -1076,25 +1076,41 @@ EXPORT_SYMBOL_GPL(iommu_put_tce_user_mode);
int iommu_take_ownership(struct iommu_table *tbl)
{
unsigned long sz = (tbl->it_size + 7) >> 3;
+ int i, ret = 0;
+
+ for (i = 0; i < tbl->nr_pools; i++)
+ spin_lock(&tbl->pools[i].lock);
+ spin_lock(&tbl->large_pool.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;
+ goto unlock_exit;
}

memset(tbl->it_map, 0xff, sz);
iommu_clear_tces_and_put_pages(tbl, tbl->it_offset, tbl->it_size);

- return 0;
+unlock_exit:
+ spin_unlock(&tbl->large_pool.lock);
+ for (i = 0; i < tbl->nr_pools; i++)
+ spin_unlock(&tbl->pools[i].lock);
+
+ return ret;
}
EXPORT_SYMBOL_GPL(iommu_take_ownership);

void iommu_release_ownership(struct iommu_table *tbl)
{
unsigned long sz = (tbl->it_size + 7) >> 3;
+ int i;
+
+ for (i = 0; i < tbl->nr_pools; i++)
+ spin_lock(&tbl->pools[i].lock);
+ spin_lock(&tbl->large_pool.lock);

iommu_clear_tces_and_put_pages(tbl, tbl->it_offset, tbl->it_size);
memset(tbl->it_map, 0, sz);
@@ -1102,6 +1118,11 @@ 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);
+
+ spin_unlock(&tbl->large_pool.lock);
+ for (i = 0; i < tbl->nr_pools; i++)
+ spin_unlock(&tbl->pools[i].lock);
+
}
EXPORT_SYMBOL_GPL(iommu_release_ownership);

--
1.7.10.4

2013-06-26 05:50:14

by Benjamin Herrenschmidt

Subject: Re: [PATCH] powerpc/vfio: Add missing locks for take/release TCE table ownership

On Wed, 2013-06-26 at 15:39 +1000, Alexey Kardashevskiy wrote:
> VFIO IOMMU driver for sPAPR TCE locks the whole DMA window by setting
> ones to iommu_table.it_map. However this was not protected by the locks
> which other clients of iommu_table use.
>
> The patch fixes this.
>
> Signed-off-by: Alexey Kardashevskiy <[email protected]>
> ---
> arch/powerpc/kernel/iommu.c | 25 +++++++++++++++++++++++--
> 1 file changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
> index b20ff17..9f34742 100644
> --- a/arch/powerpc/kernel/iommu.c
> +++ b/arch/powerpc/kernel/iommu.c
> @@ -1076,25 +1076,41 @@ EXPORT_SYMBOL_GPL(iommu_put_tce_user_mode);
> int iommu_take_ownership(struct iommu_table *tbl)
> {
> unsigned long sz = (tbl->it_size + 7) >> 3;
> + int i, ret = 0;
> +
> + for (i = 0; i < tbl->nr_pools; i++)
> + spin_lock(&tbl->pools[i].lock);
> + spin_lock(&tbl->large_pool.lock);

IOMMUs can be used at interrupt time so the above will trigger lockdep
warnings unless you also bracket the whole function in
local_irq_save/restore.

Now you *shouldn't* be racing since afaik you only take the iommu
ownership after no more drivers are hooked up, but better safe than
sorry.

Cheers,
Ben.


> 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;
> + goto unlock_exit;
> }
>
> memset(tbl->it_map, 0xff, sz);
> iommu_clear_tces_and_put_pages(tbl, tbl->it_offset, tbl->it_size);
>
> - return 0;
> +unlock_exit:
> + spin_unlock(&tbl->large_pool.lock);
> + for (i = 0; i < tbl->nr_pools; i++)
> + spin_unlock(&tbl->pools[i].lock);
> +
> + return ret;
> }
> EXPORT_SYMBOL_GPL(iommu_take_ownership);
>
> void iommu_release_ownership(struct iommu_table *tbl)
> {
> unsigned long sz = (tbl->it_size + 7) >> 3;
> + int i;
> +
> + for (i = 0; i < tbl->nr_pools; i++)
> + spin_lock(&tbl->pools[i].lock);
> + spin_lock(&tbl->large_pool.lock);
>
> iommu_clear_tces_and_put_pages(tbl, tbl->it_offset, tbl->it_size);
> memset(tbl->it_map, 0, sz);
> @@ -1102,6 +1118,11 @@ 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);
> +
> + spin_unlock(&tbl->large_pool.lock);
> + for (i = 0; i < tbl->nr_pools; i++)
> + spin_unlock(&tbl->pools[i].lock);
> +
> }
> EXPORT_SYMBOL_GPL(iommu_release_ownership);
>