Hi, Nirmoy, Christian
On Fri, 2024-08-16 at 15:51 +0200, Nirmoy Das wrote:
> Add TTM_TT_FLAG_CLEARED_ON_FREE, which DRM drivers can set before
> releasing backing stores if they want to skip clear-on-free.
>
> Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
> Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> Suggested-by: Christian König <christian.koenig@xxxxxxx>
> Signed-off-by: Nirmoy Das <nirmoy.das@xxxxxxxxx>
> Reviewed-by: Christian König <christian.koenig@xxxxxxx>
What happens if two devices share the same global TTM pool
type and one that does its own clearing. Wouldn't there be a pretty
high chance that the the device that doesn't clear its own pages
allocate non-cleared memory from the pool?
/Thomas
> ---
> drivers/gpu/drm/ttm/ttm_pool.c | 18 +++++++++++-------
> include/drm/ttm/ttm_tt.h | 6 +++++-
> 2 files changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_pool.c
> b/drivers/gpu/drm/ttm/ttm_pool.c
> index 8504dbe19c1a..935ab3cfd046 100644
> --- a/drivers/gpu/drm/ttm/ttm_pool.c
> +++ b/drivers/gpu/drm/ttm/ttm_pool.c
> @@ -222,15 +222,18 @@ static void ttm_pool_unmap(struct ttm_pool
> *pool, dma_addr_t dma_addr,
> }
>
> /* Give pages into a specific pool_type */
> -static void ttm_pool_type_give(struct ttm_pool_type *pt, struct page
> *p)
> +static void ttm_pool_type_give(struct ttm_pool_type *pt, struct page
> *p,
> + bool cleared)
> {
> unsigned int i, num_pages = 1 << pt->order;
>
> - for (i = 0; i < num_pages; ++i) {
> - if (PageHighMem(p))
> - clear_highpage(p + i);
> - else
> - clear_page(page_address(p + i));
> + if (!cleared) {
> + for (i = 0; i < num_pages; ++i) {
> + if (PageHighMem(p))
> + clear_highpage(p + i);
> + else
> + clear_page(page_address(p + i));
> + }
> }
>
> spin_lock(&pt->lock);
> @@ -394,6 +397,7 @@ static void ttm_pool_free_range(struct ttm_pool
> *pool, struct ttm_tt *tt,
> pgoff_t start_page, pgoff_t
> end_page)
> {
> struct page **pages = &tt->pages[start_page];
> + bool cleared = tt->page_flags & TTM_TT_FLAG_CLEARED_ON_FREE;
> unsigned int order;
> pgoff_t i, nr;
>
> @@ -407,7 +411,7 @@ static void ttm_pool_free_range(struct ttm_pool
> *pool, struct ttm_tt *tt,
>
> pt = ttm_pool_select_type(pool, caching, order);
> if (pt)
> - ttm_pool_type_give(pt, *pages);
> + ttm_pool_type_give(pt, *pages, cleared);
> else
> ttm_pool_free_page(pool, caching, order,
> *pages);
> }
> diff --git a/include/drm/ttm/ttm_tt.h b/include/drm/ttm/ttm_tt.h
> index 2b9d856ff388..cfaf49de2419 100644
> --- a/include/drm/ttm/ttm_tt.h
> +++ b/include/drm/ttm/ttm_tt.h
> @@ -85,6 +85,9 @@ struct ttm_tt {
> * fault handling abuses the DMA api a bit and dma_map_attrs
> can't be
> * used to assure pgprot always matches.
> *
> + * TTM_TT_FLAG_CLEARED_ON_FREE: Set this if a drm driver
> handles
> + * clearing backing store
> + *
> * TTM_TT_FLAG_PRIV_POPULATED: TTM internal only. DO NOT
> USE. This is
> * set by TTM after ttm_tt_populate() has successfully
> returned, and is
> * then unset when TTM calls ttm_tt_unpopulate().
> @@ -94,8 +97,9 @@ struct ttm_tt {
> #define TTM_TT_FLAG_EXTERNAL BIT(2)
> #define TTM_TT_FLAG_EXTERNAL_MAPPABLE BIT(3)
> #define TTM_TT_FLAG_DECRYPTED BIT(4)
> +#define TTM_TT_FLAG_CLEARED_ON_FREE BIT(5)
>
> -#define TTM_TT_FLAG_PRIV_POPULATED BIT(5)
> +#define TTM_TT_FLAG_PRIV_POPULATED BIT(6)
> uint32_t page_flags;
> /** @num_pages: Number of pages in the page array. */
> uint32_t num_pages;
