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    Subject[PATCH 4.13 28/47] drm/vgem: Pin our pages for dmabuf exports
    Date
    4.13-stable review patch.  If anyone has any objections, please let me know.

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

    From: Chris Wilson <chris@chris-wilson.co.uk>

    commit 71bb23c707c141b176bc084179ca5ee58d5fd26a upstream.

    When the caller maps their dmabuf and we return an sg_table, the caller
    doesn't expect the pages beneath that sg_table to vanish on a whim (i.e.
    under mempressure). The contract is that the pages are pinned for the
    duration of the mapping (from dma_buf_map_attachment() to
    dma_buf_unmap_attachment). To comply, we need to introduce our own
    vgem_object.pages_pin_count and elevate it across the mapping. However,
    the drm_prime interface we use calls drv->prime_pin on dma_buf_attach
    and drv->prime_unpin on dma_buf_detach, which while that does cover the
    mapping is much broader than is desired -- but it will do for now.

    v2: also hold the pin across prime_vmap/vunmap

    Reported-by: Tomi Sarvela <tomi.p.sarvela@intel.com>
    Testcase: igt/gem_concurrent_blit/*swap*vgem*
    Fixes: 5ba6c9ff961a ("drm/vgem: Fix mmaping")
    Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
    Cc: Tomi Sarvela <tomi.p.sarvela@intel.com>
    Cc: Laura Abbott <labbott@redhat.com>
    Cc: Sean Paul <seanpaul@chromium.org>
    Cc: Matthew Auld <matthew.auld@intel.com>
    Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
    Cc: <stable@vger.kernel.org> # needs a backport
    Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
    Link: http://patchwork.freedesktop.org/patch/msgid/20170622134617.17912-1-chris@chris-wilson.co.uk
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/gpu/drm/vgem/vgem_drv.c | 81 +++++++++++++++++++++++++++++-----------
    drivers/gpu/drm/vgem/vgem_drv.h | 4 +
    2 files changed, 64 insertions(+), 21 deletions(-)

    --- a/drivers/gpu/drm/vgem/vgem_drv.c
    +++ b/drivers/gpu/drm/vgem/vgem_drv.c
    @@ -52,6 +52,7 @@ static void vgem_gem_free_object(struct
    struct drm_vgem_gem_object *vgem_obj = to_vgem_bo(obj);

    kvfree(vgem_obj->pages);
    + mutex_destroy(&vgem_obj->pages_lock);

    if (obj->import_attach)
    drm_prime_gem_destroy(obj, vgem_obj->table);
    @@ -76,11 +77,15 @@ static int vgem_gem_fault(struct vm_faul
    if (page_offset > num_pages)
    return VM_FAULT_SIGBUS;

    + ret = -ENOENT;
    + mutex_lock(&obj->pages_lock);
    if (obj->pages) {
    get_page(obj->pages[page_offset]);
    vmf->page = obj->pages[page_offset];
    ret = 0;
    - } else {
    + }
    + mutex_unlock(&obj->pages_lock);
    + if (ret) {
    struct page *page;

    page = shmem_read_mapping_page(
    @@ -161,6 +166,8 @@ static struct drm_vgem_gem_object *__vge
    return ERR_PTR(ret);
    }

    + mutex_init(&obj->pages_lock);
    +
    return obj;
    }

    @@ -274,37 +281,66 @@ static const struct file_operations vgem
    .release = drm_release,
    };

    +static struct page **vgem_pin_pages(struct drm_vgem_gem_object *bo)
    +{
    + mutex_lock(&bo->pages_lock);
    + if (bo->pages_pin_count++ == 0) {
    + struct page **pages;
    +
    + pages = drm_gem_get_pages(&bo->base);
    + if (IS_ERR(pages)) {
    + bo->pages_pin_count--;
    + mutex_unlock(&bo->pages_lock);
    + return pages;
    + }
    +
    + bo->pages = pages;
    + }
    + mutex_unlock(&bo->pages_lock);
    +
    + return bo->pages;
    +}
    +
    +static void vgem_unpin_pages(struct drm_vgem_gem_object *bo)
    +{
    + mutex_lock(&bo->pages_lock);
    + if (--bo->pages_pin_count == 0) {
    + drm_gem_put_pages(&bo->base, bo->pages, true, true);
    + bo->pages = NULL;
    + }
    + mutex_unlock(&bo->pages_lock);
    +}
    +
    static int vgem_prime_pin(struct drm_gem_object *obj)
    {
    + struct drm_vgem_gem_object *bo = to_vgem_bo(obj);
    long n_pages = obj->size >> PAGE_SHIFT;
    struct page **pages;

    - /* Flush the object from the CPU cache so that importers can rely
    - * on coherent indirect access via the exported dma-address.
    - */
    - pages = drm_gem_get_pages(obj);
    + pages = vgem_pin_pages(bo);
    if (IS_ERR(pages))
    return PTR_ERR(pages);

    + /* Flush the object from the CPU cache so that importers can rely
    + * on coherent indirect access via the exported dma-address.
    + */
    drm_clflush_pages(pages, n_pages);
    - drm_gem_put_pages(obj, pages, true, false);

    return 0;
    }

    -static struct sg_table *vgem_prime_get_sg_table(struct drm_gem_object *obj)
    +static void vgem_prime_unpin(struct drm_gem_object *obj)
    {
    - struct sg_table *st;
    - struct page **pages;
    + struct drm_vgem_gem_object *bo = to_vgem_bo(obj);

    - pages = drm_gem_get_pages(obj);
    - if (IS_ERR(pages))
    - return ERR_CAST(pages);
    + vgem_unpin_pages(bo);
    +}

    - st = drm_prime_pages_to_sg(pages, obj->size >> PAGE_SHIFT);
    - drm_gem_put_pages(obj, pages, false, false);
    +static struct sg_table *vgem_prime_get_sg_table(struct drm_gem_object *obj)
    +{
    + struct drm_vgem_gem_object *bo = to_vgem_bo(obj);

    - return st;
    + return drm_prime_pages_to_sg(bo->pages, bo->base.size >> PAGE_SHIFT);
    }

    static struct drm_gem_object* vgem_prime_import(struct drm_device *dev,
    @@ -333,6 +369,8 @@ static struct drm_gem_object *vgem_prime
    __vgem_gem_destroy(obj);
    return ERR_PTR(-ENOMEM);
    }
    +
    + obj->pages_pin_count++; /* perma-pinned */
    drm_prime_sg_to_page_addr_arrays(obj->table, obj->pages, NULL,
    npages);
    return &obj->base;
    @@ -340,23 +378,23 @@ static struct drm_gem_object *vgem_prime

    static void *vgem_prime_vmap(struct drm_gem_object *obj)
    {
    + struct drm_vgem_gem_object *bo = to_vgem_bo(obj);
    long n_pages = obj->size >> PAGE_SHIFT;
    struct page **pages;
    - void *addr;

    - pages = drm_gem_get_pages(obj);
    + pages = vgem_pin_pages(bo);
    if (IS_ERR(pages))
    return NULL;

    - addr = vmap(pages, n_pages, 0, pgprot_writecombine(PAGE_KERNEL));
    - drm_gem_put_pages(obj, pages, false, false);
    -
    - return addr;
    + return vmap(pages, n_pages, 0, pgprot_writecombine(PAGE_KERNEL));
    }

    static void vgem_prime_vunmap(struct drm_gem_object *obj, void *vaddr)
    {
    + struct drm_vgem_gem_object *bo = to_vgem_bo(obj);
    +
    vunmap(vaddr);
    + vgem_unpin_pages(bo);
    }

    static int vgem_prime_mmap(struct drm_gem_object *obj,
    @@ -409,6 +447,7 @@ static struct drm_driver vgem_driver = {
    .prime_handle_to_fd = drm_gem_prime_handle_to_fd,
    .prime_fd_to_handle = drm_gem_prime_fd_to_handle,
    .gem_prime_pin = vgem_prime_pin,
    + .gem_prime_unpin = vgem_prime_unpin,
    .gem_prime_import = vgem_prime_import,
    .gem_prime_export = drm_gem_prime_export,
    .gem_prime_import_sg_table = vgem_prime_import_sg_table,
    --- a/drivers/gpu/drm/vgem/vgem_drv.h
    +++ b/drivers/gpu/drm/vgem/vgem_drv.h
    @@ -43,7 +43,11 @@ struct vgem_file {
    #define to_vgem_bo(x) container_of(x, struct drm_vgem_gem_object, base)
    struct drm_vgem_gem_object {
    struct drm_gem_object base;
    +
    struct page **pages;
    + unsigned int pages_pin_count;
    + struct mutex pages_lock;
    +
    struct sg_table *table;
    };


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