Messages in this thread | | | Subject | Re: [PATCH] powerpc/vfio: Add missing locks for take/release TCE table ownership | From | Benjamin Herrenschmidt <> | Date | Wed, 26 Jun 2013 15:49:55 +1000 |
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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 <aik@ozlabs.ru> > --- > 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); >
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