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powerpc/powernv/ioda: Fix locked_vm counting for memory used by IOMMU tables

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[ Upstream commit 11f5acce2f ]

We store 2 multilevel tables in iommu_table - one for the hardware and
one with the corresponding userspace addresses. Before allocating
the tables, the iommu_table_group_ops::get_table_size() hook returns
the combined size of the two and VFIO SPAPR TCE IOMMU driver adjusts
the locked_vm counter correctly. When the table is actually allocated,
the amount of allocated memory is stored in iommu_table::it_allocated_size
and used to decrement the locked_vm counter when we release the memory
used by the table; .get_table_size() and .create_table() calculate it
independently but the result is expected to be the same.

However the allocator does not add the userspace table size to
.it_allocated_size so when we destroy the table because of VFIO PCI
unplug (i.e. VFIO container is gone but the userspace keeps running),
we decrement locked_vm by just a half of size of memory we are
releasing.

To make things worse, since we enabled on-demand allocation of
indirect levels, it_allocated_size contains only the amount of memory
actually allocated at the table creation time which can just be a
fraction. It is not a problem with incrementing locked_vm (as
get_table_size() value is used) but it is with decrementing.

As the result, we leak locked_vm and may not be able to allocate more
IOMMU tables after few iterations of hotplug/unplug.

This sets it_allocated_size in the pnv_pci_ioda2_ops::create_table()
hook to what pnv_pci_ioda2_get_table_size() returns so from now on we
have a single place which calculates the maximum memory a table can
occupy. The original meaning of it_allocated_size is somewhat lost now
though.

We do not ditch it_allocated_size whatsoever here and we do not call
get_table_size() from vfio_iommu_spapr_tce.c when decrementing
locked_vm as we may have multiple IOMMU groups per container and even
though they all are supposed to have the same get_table_size()
implementation, there is a small chance for failure or confusion.

Fixes: 090bad39b2 ("powerpc/powernv: Add indirect levels to it_userspace")
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Alexey Kardashevskiy 2019-02-13 14:38:18 +11:00 • committed by Greg Kroah-Hartman
commit 4acf797458
2 changed files with 6 additions and 2 deletions
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1
arch/powerpc/platforms/powernv/pci-ioda-tce.c
View file

@ -313,7 +313,6 @@ long pnv_pci_ioda2_table_alloc_pages(int nid, __u64 bus_offset,
page_shift);
tbl->it_level_size = 1ULL << (level_shift - 3);
tbl->it_indirect_levels = levels - 1;
tbl->it_allocated_size = total_allocated;
tbl->it_userspace = uas;
tbl->it_nid = nid;

7
arch/powerpc/platforms/powernv/pci-ioda.c
View file

@ -2603,8 +2603,13 @@ static long pnv_pci_ioda2_create_table_userspace(
int num, __u32 page_shift, __u64 window_size, __u32 levels,
struct iommu_table **ptbl)
{
return pnv_pci_ioda2_create_table(table_group,
long ret = pnv_pci_ioda2_create_table(table_group,
num, page_shift, window_size, levels, true, ptbl);
if (!ret)
(*ptbl)->it_allocated_size = pnv_pci_ioda2_get_table_size(
page_shift, window_size, levels);
return ret;
}
static void pnv_ioda2_take_ownership(struct iommu_table_group *table_group)