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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? You are right, mixing such devices will poison the global pool. Unfortunately, I fully concentrated on single device use-case. This is problematic mainly because on XE, we are doing clear on alloc so from ttm prospective the flag is correct. A quick option would be to limit this for non-pooled allocations on XE or even create a separate pool for XE when have this gpu-system-page-clear is enabled. Thanks for catching this, I will test above options and send patches to fix the xe commit. Regards, Nirmoy > > /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;