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    Subject[PATCH 4.9 69/93] vfio/spapr: Postpone default window creation
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

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

    From: Alexey Kardashevskiy <aik@ozlabs.ru>

    [ Upstream commit d9c728949ddc9de5734bf3b12ea906ca8a77f2a0 ]

    We are going to allow the userspace to configure container in
    one memory context and pass container fd to another so
    we are postponing memory allocations accounted against
    the locked memory limit. One of previous patches took care of
    it_userspace.

    At the moment we create the default DMA window when the first group is
    attached to a container; this is done for the userspace which is not
    DDW-aware but familiar with the SPAPR TCE IOMMU v2 in the part of memory
    pre-registration - such client expects the default DMA window to exist.

    This postpones the default DMA window allocation till one of
    the folliwing happens:
    1. first map/unmap request arrives;
    2. new window is requested;
    This adds noop for the case when the userspace requested removal
    of the default window which has not been created yet.

    Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
    Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
    Acked-by: Alex Williamson <alex.williamson@redhat.com>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/vfio/vfio_iommu_spapr_tce.c | 40 ++++++++++++++++++++++--------------
    1 file changed, 25 insertions(+), 15 deletions(-)

    --- a/drivers/vfio/vfio_iommu_spapr_tce.c
    +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
    @@ -106,6 +106,7 @@ struct tce_container {
    struct mutex lock;
    bool enabled;
    bool v2;
    + bool def_window_pending;
    unsigned long locked_pages;
    struct mm_struct *mm;
    struct iommu_table *tables[IOMMU_TABLE_GROUP_MAX_TABLES];
    @@ -791,6 +792,9 @@ static long tce_iommu_create_default_win
    struct tce_iommu_group *tcegrp;
    struct iommu_table_group *table_group;

    + if (!container->def_window_pending)
    + return 0;
    +
    if (!tce_groups_attached(container))
    return -ENODEV;

    @@ -804,6 +808,9 @@ static long tce_iommu_create_default_win
    table_group->tce32_size, 1, &start_addr);
    WARN_ON_ONCE(!ret && start_addr);

    + if (!ret)
    + container->def_window_pending = false;
    +
    return ret;
    }

    @@ -907,6 +914,10 @@ static long tce_iommu_ioctl(void *iommu_
    VFIO_DMA_MAP_FLAG_WRITE))
    return -EINVAL;

    + ret = tce_iommu_create_default_window(container);
    + if (ret)
    + return ret;
    +
    num = tce_iommu_find_table(container, param.iova, &tbl);
    if (num < 0)
    return -ENXIO;
    @@ -970,6 +981,10 @@ static long tce_iommu_ioctl(void *iommu_
    if (param.flags)
    return -EINVAL;

    + ret = tce_iommu_create_default_window(container);
    + if (ret)
    + return ret;
    +
    num = tce_iommu_find_table(container, param.iova, &tbl);
    if (num < 0)
    return -ENXIO;
    @@ -1107,6 +1122,10 @@ static long tce_iommu_ioctl(void *iommu_

    mutex_lock(&container->lock);

    + ret = tce_iommu_create_default_window(container);
    + if (ret)
    + return ret;
    +
    ret = tce_iommu_create_window(container, create.page_shift,
    create.window_size, create.levels,
    &create.start_addr);
    @@ -1143,6 +1162,11 @@ static long tce_iommu_ioctl(void *iommu_
    if (remove.flags)
    return -EINVAL;

    + if (container->def_window_pending && !remove.start_addr) {
    + container->def_window_pending = false;
    + return 0;
    + }
    +
    mutex_lock(&container->lock);

    ret = tce_iommu_remove_window(container, remove.start_addr);
    @@ -1240,7 +1264,6 @@ static int tce_iommu_attach_group(void *
    struct tce_container *container = iommu_data;
    struct iommu_table_group *table_group;
    struct tce_iommu_group *tcegrp = NULL;
    - bool create_default_window = false;

    mutex_lock(&container->lock);

    @@ -1288,25 +1311,12 @@ static int tce_iommu_attach_group(void *
    } else {
    ret = tce_iommu_take_ownership_ddw(container, table_group);
    if (!tce_groups_attached(container) && !container->tables[0])
    - create_default_window = true;
    + container->def_window_pending = true;
    }

    if (!ret) {
    tcegrp->grp = iommu_group;
    list_add(&tcegrp->next, &container->group_list);
    - /*
    - * If it the first group attached, check if there is
    - * a default DMA window and create one if none as
    - * the userspace expects it to exist.
    - */
    - if (create_default_window) {
    - ret = tce_iommu_create_default_window(container);
    - if (ret) {
    - list_del(&tcegrp->next);
    - tce_iommu_release_ownership_ddw(container,
    - table_group);
    - }
    - }
    }

    unlock_exit:

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