[RFC PATCH 02/16] drm/ttm/pool: Fix ttm_pool_alloc error path
Thomas Hellström
thomas.hellstrom at linux.intel.com
Wed Feb 15 18:02:37 UTC 2023
On Wed, 2023-02-15 at 18:31 +0100, Christian König wrote:
> Am 15.02.23 um 17:13 schrieb Thomas Hellström:
> > When hitting an error, the error path forgot to unmap dma mappings
> > and
>
> I don't see where this happens?
From what I can tell, ttm_pool_page_allocated() maps the page for dma,
If we later hit an error, ttm_pool_free_page() will leak the mapping.
>
> > could call set_pages_wb() on already uncached pages.
>
> Yeah, but what's the problem?
Umm, at least if you try to set WC on an already WC'd page, the
set_pages_ code will spam dmesg with warnings.
Not sure if set_pages_wb() on WB pages does the same, nor if it
issues unnecessary global cache / tlb flushes or whether that will
change in the future.
The point of avoiding the set_pages_wb() when already WB is you don't
have to check, and you don't have to care.
That said, the __ttm_pool_free() is used also in upcoming patches.
/Thomas
>
> Regards,
> Christian.
>
> >
> > Fix this by introducing a common __ttm_pool_free() function that
> > does the right thing.
> >
> > Fixes: d099fc8f540a ("drm/ttm: new TT backend allocation pool v3")
> > Cc: Christian König <christian.koenig at amd.com>
> > Cc: Dave Airlie <airlied at redhat.com>
> > Cc: Madhav Chauhan <madhav.chauhan at amd.com>
> > Cc: Christian Koenig <christian.koenig at amd.com>
> > Cc: Huang Rui <ray.huang at amd.com>
> > Cc: dri-devel at lists.freedesktop.org
> > Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> > ---
> > drivers/gpu/drm/ttm/ttm_pool.c | 74 +++++++++++++++++++++--------
> > -----
> > 1 file changed, 45 insertions(+), 29 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/ttm/ttm_pool.c
> > b/drivers/gpu/drm/ttm/ttm_pool.c
> > index aa116a7bbae3..1cc7591a9542 100644
> > --- a/drivers/gpu/drm/ttm/ttm_pool.c
> > +++ b/drivers/gpu/drm/ttm/ttm_pool.c
> > @@ -367,6 +367,39 @@ static int ttm_pool_page_allocated(struct
> > ttm_pool *pool, unsigned int order,
> > return 0;
> > }
> >
> > +static void __ttm_pool_free(struct ttm_pool *pool, struct ttm_tt
> > *tt,
> > + struct page **caching_divide,
> > + enum ttm_caching initial_caching,
> > + enum ttm_caching subseq_caching,
> > + pgoff_t num_pages)
> > +{
> > + enum ttm_caching caching = subseq_caching;
> > + struct page **pages = tt->pages;
> > + unsigned int order;
> > + pgoff_t i, nr;
> > +
> > + if (pool && caching_divide)
> > + caching = initial_caching;
> > +
> > + for (i = 0; i < num_pages; i += nr, pages += nr) {
> > + struct ttm_pool_type *pt = NULL;
> > +
> > + if (unlikely(caching_divide == pages))
> > + caching = subseq_caching;
> > +
> > + order = ttm_pool_page_order(pool, *pages);
> > + nr = (1UL << order);
> > + if (tt->dma_address)
> > + ttm_pool_unmap(pool, tt->dma_address[i],
> > nr);
> > +
> > + pt = ttm_pool_select_type(pool, caching, order);
> > + if (pt)
> > + ttm_pool_type_give(pt, *pages);
> > + else
> > + ttm_pool_free_page(pool, caching, order,
> > *pages);
> > + }
> > +}
> > +
> > /**
> > * ttm_pool_alloc - Fill a ttm_tt object
> > *
> > @@ -386,8 +419,9 @@ int ttm_pool_alloc(struct ttm_pool *pool,
> > struct ttm_tt *tt,
> > dma_addr_t *dma_addr = tt->dma_address;
> > struct page **caching = tt->pages;
> > struct page **pages = tt->pages;
> > + enum ttm_caching page_caching;
> > gfp_t gfp_flags = GFP_USER;
> > - unsigned int i, order;
> > + unsigned int order;
> > struct page *p;
> > int r;
> >
> > @@ -410,6 +444,7 @@ int ttm_pool_alloc(struct ttm_pool *pool,
> > struct ttm_tt *tt,
> > order = min_t(unsigned int, order, __fls(num_pages)))
> > {
> > struct ttm_pool_type *pt;
> >
> > + page_caching = tt->caching;
> > pt = ttm_pool_select_type(pool, tt->caching,
> > order);
> > p = pt ? ttm_pool_type_take(pt) : NULL;
> > if (p) {
> > @@ -418,6 +453,7 @@ int ttm_pool_alloc(struct ttm_pool *pool,
> > struct ttm_tt *tt,
> > if (r)
> > goto error_free_page;
> >
> > + caching = pages;
> > do {
> > r = ttm_pool_page_allocated(pool,
> > order, p,
> >
> > &dma_addr,
> > @@ -426,14 +462,15 @@ int ttm_pool_alloc(struct ttm_pool *pool,
> > struct ttm_tt *tt,
> > if (r)
> > goto error_free_page;
> >
> > + caching = pages;
> > if (num_pages < (1 << order))
> > break;
> >
> > p = ttm_pool_type_take(pt);
> > } while (p);
> > - caching = pages;
> > }
> >
> > + page_caching = ttm_cached;
> > while (num_pages >= (1 << order) &&
> > (p = ttm_pool_alloc_page(pool, gfp_flags,
> > order))) {
> >
> > @@ -442,6 +479,7 @@ int ttm_pool_alloc(struct ttm_pool *pool,
> > struct ttm_tt *tt,
> > tt-
> > >caching);
> > if (r)
> > goto error_free_page;
> > + caching = pages;
> > }
> > r = ttm_pool_page_allocated(pool, order, p,
> > &dma_addr,
> > &num_pages,
> > &pages);
> > @@ -468,15 +506,12 @@ int ttm_pool_alloc(struct ttm_pool *pool,
> > struct ttm_tt *tt,
> > return 0;
> >
> > error_free_page:
> > - ttm_pool_free_page(pool, tt->caching, order, p);
> > + ttm_pool_free_page(pool, page_caching, order, p);
> >
> > error_free_all:
> > num_pages = tt->num_pages - num_pages;
> > - for (i = 0; i < num_pages; ) {
> > - order = ttm_pool_page_order(pool, tt->pages[i]);
> > - ttm_pool_free_page(pool, tt->caching, order, tt-
> > >pages[i]);
> > - i += 1 << order;
> > - }
> > + __ttm_pool_free(pool, tt, caching, tt->caching, ttm_cached,
> > + num_pages);
> >
> > return r;
> > }
> > @@ -492,27 +527,8 @@ EXPORT_SYMBOL(ttm_pool_alloc);
> > */
> > void ttm_pool_free(struct ttm_pool *pool, struct ttm_tt *tt)
> > {
> > - unsigned int i;
> > -
> > - for (i = 0; i < tt->num_pages; ) {
> > - struct page *p = tt->pages[i];
> > - unsigned int order, num_pages;
> > - struct ttm_pool_type *pt;
> > -
> > - order = ttm_pool_page_order(pool, p);
> > - num_pages = 1ULL << order;
> > - if (tt->dma_address)
> > - ttm_pool_unmap(pool, tt->dma_address[i],
> > num_pages);
> > -
> > - pt = ttm_pool_select_type(pool, tt->caching,
> > order);
> > - if (pt)
> > - ttm_pool_type_give(pt, tt->pages[i]);
> > - else
> > - ttm_pool_free_page(pool, tt->caching,
> > order,
> > - tt->pages[i]);
> > -
> > - i += num_pages;
> > - }
> > + __ttm_pool_free(pool, tt, NULL, tt->caching, tt->caching,
> > + tt->num_pages);
> >
> > while (atomic_long_read(&allocated_pages) > page_pool_size)
> > ttm_pool_shrink();
>
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