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    Subject[PATCH 5.0 067/246] powerpc/powernv/ioda: Fix locked_vm counting for memory used by IOMMU tables
    Date
    5.0-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    [ Upstream commit 11f5acce2fa43b015a8120fa7620fa4efd0a2952 ]

    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: 090bad39b237 ("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>
    ---
    arch/powerpc/platforms/powernv/pci-ioda-tce.c | 1 -
    arch/powerpc/platforms/powernv/pci-ioda.c | 7 ++++++-
    2 files changed, 6 insertions(+), 2 deletions(-)

    diff --git a/arch/powerpc/platforms/powernv/pci-ioda-tce.c b/arch/powerpc/platforms/powernv/pci-ioda-tce.c
    index 697449afb3f7..e28f03e1eb5e 100644
    --- a/arch/powerpc/platforms/powernv/pci-ioda-tce.c
    +++ b/arch/powerpc/platforms/powernv/pci-ioda-tce.c
    @@ -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;

    diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
    index 145373f0e5dc..2d62c58f9a4c 100644
    --- a/arch/powerpc/platforms/powernv/pci-ioda.c
    +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
    @@ -2594,8 +2594,13 @@ 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)
    --
    2.19.1


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