On Wed, Jul 03, 2024 at 05:38:11PM +0200, Thomas Hellström wrote:
> Use fault-injection to test partial TTM swapout and interrupted swapin.
> Return -EINTR for swapin to test the callers ability to handle and
> restart the swapin, and on swapout perform a partial swapout to test that
> the swapin and release_shrunken functionality.
>
> Cc: Christian König <christian.koenig@xxxxxxx>
> Cc: Somalapuram Amaranath <Amaranath.Somalapuram@xxxxxxx>
> Cc: Matthew Brost <matthew.brost@xxxxxxxxx>
> Cc: <dri-devel@xxxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/Kconfig | 10 ++++++++++
> drivers/gpu/drm/ttm/ttm_pool.c | 17 ++++++++++++++++-
> 2 files changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index fd0749c0c630..9f27271bfab8 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -272,6 +272,16 @@ config DRM_GPUVM
> GPU-VM representation providing helpers to manage a GPUs virtual
> address space
>
> +config DRM_TTM_BACKUP_FAULT_INJECT
> + bool "Enable fault injection during TTM backup"
> + depends on DRM_TTM
> + default n
> + help
> + Inject recoverable failures during TTM backup and recovery of
> + backed-up objects. For DRM driver developers only.
> +
> + If in doubt, choose N.
> +
> config DRM_BUDDY
> tristate
> depends on DRM
> diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
> index 38e50cf81b0a..d32a1f2e5e50 100644
> --- a/drivers/gpu/drm/ttm/ttm_pool.c
> +++ b/drivers/gpu/drm/ttm/ttm_pool.c
> @@ -431,6 +431,7 @@ static int ttm_pool_restore_tt(struct ttm_pool_tt_restore *restore,
> struct ttm_backup *backup,
> struct ttm_operation_ctx *ctx)
> {
> + static unsigned long __maybe_unused swappedin;
> unsigned int i, nr = 1 << restore->order;
> int ret = 0;
>
> @@ -446,6 +447,13 @@ static int ttm_pool_restore_tt(struct ttm_pool_tt_restore *restore,
> if (handle == 0)
> continue;
>
> + if (IS_ENABLED(CONFIG_DRM_TTM_BACKUP_FAULT_INJECT) &&
> + ctx->interruptible &&
> + ++swappedin % 100 == 0) {
> + ret = -EINTR;
> + break;
> + }
So here this -EINTR would be kicked to the user IOCTL which triggered
the BO validate and retry? The restore then should be able to
successfully pick up where it left off?
> +
> ret = backup->ops->copy_backed_up_page
> (backup, restore->first_page[i],
> handle, ctx->interruptible);
> @@ -892,7 +900,14 @@ long ttm_pool_backup_tt(struct ttm_pool *pool, struct ttm_tt *ttm, bool purge,
>
> alloc_gfp = GFP_KERNEL | __GFP_HIGH | __GFP_NOWARN | __GFP_RETRY_MAYFAIL;
>
> - for (i = 0; i < ttm->num_pages; ++i) {
> + num_pages = ttm->num_pages;
> +
> + /* Pretend doing fault injection by shrinking only half of the pages. */
> +
> + if (IS_ENABLED(CONFIG_DRM_TTM_BACKUP_FAULT_INJECT))
> + num_pages = DIV_ROUND_UP(num_pages, 2);
So what happens here? Half the pages swapped out, then upon restore half
swapped back in? The shrinker continues to walk until enough pages
swapped out?
Matt
> +
> + for (i = 0; i < num_pages; ++i) {
> page = ttm->pages[i];
> if (unlikely(!page))
> continue;
> --
> 2.44.0
>
