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    SubjectRE: [PATCH v2 05/10] iommufd: Add replace support in iommufd_access_set_ioas()
    Date
    > From: Nicolin Chen <nicolinc@nvidia.com>
    > Sent: Wednesday, February 8, 2023 5:18 AM
    >
    > Support an access->ioas replacement in iommufd_access_set_ioas(), which
    > sets the access->ioas to NULL provisionally so that any further incoming
    > iommufd_access_pin_pages() callback can be blocked.
    >
    > Then, call access->ops->unmap() to clean up the entire iopt. To allow an
    > iommufd_access_unpin_pages() callback to happen via this unmap() call,
    > add an ioas_unpin pointer so the unpin routine won't be affected by the
    > "access->ioas = NULL" trick above.
    >
    > Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
    > Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>

    move patch10 before this one.

    > ---
    > drivers/iommu/iommufd/device.c | 16 ++++++++++++++--
    > drivers/iommu/iommufd/iommufd_private.h | 1 +
    > 2 files changed, 15 insertions(+), 2 deletions(-)
    >
    > diff --git a/drivers/iommu/iommufd/device.c
    > b/drivers/iommu/iommufd/device.c
    > index f4bd6f532a90..10ce47484ffa 100644
    > --- a/drivers/iommu/iommufd/device.c
    > +++ b/drivers/iommu/iommufd/device.c
    > @@ -509,11 +509,23 @@ int iommufd_access_set_ioas(struct
    > iommufd_access *access, u32 ioas_id)
    > iommufd_ref_to_users(obj);
    > }
    >
    > + /*
    > + * Set ioas to NULL to block any further iommufd_access_pin_pages().
    > + * iommufd_access_unpin_pages() can continue using access-
    > >ioas_unpin.
    > + */
    > + access->ioas = NULL;
    > +
    > if (cur_ioas) {
    > + if (new_ioas) {
    > + mutex_unlock(&access->ioas_lock);
    > + access->ops->unmap(access->data, 0, ULONG_MAX);
    > + mutex_lock(&access->ioas_lock);
    > + }

    why does above only apply to a valid new_ioas? this is the cleanup on
    cur_ioas then required even when new_ioas=NULL.

    Instead here the check should be "if (access->ops->unmap)". with
    patch10 the cleanup is required only for driver which is allowed to
    pin pages.

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