From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 29E493D1707 for ; Fri, 10 Jul 2026 21:54:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783720499; cv=none; b=szJFGLcThmPV9kwC1VESkmsk/wi0nWVT88nrqVvSLPbi87emZU/m4ya1A38EP3okLIGuEvFv8z2CHHC7SwapBQz5v7PHwWpSn3zca+LtEC0Ebib5Bk0PXIf64CY23Oa/mB4V7bJbmn0OrGqkQNTZSzVsVan76MxR5io+Yj0wJ0s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783720499; c=relaxed/simple; bh=CRsufZHSl8mAGIVIzULD/lVBN6+M2i7HeN/b1zpdF34=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=DlqKY9sO5oc56TEGLkW2ypnurQmZZaThqe8l9WDBFY78cdxGS8TmdC0dgsk7PtD9kgxcXuZMR63yiOc1JrmBvgK01hwGUjj/pDMjK/KdRjC7XzzLk6xxEdTIMOQEPQw7IsP2wwikjdekiiRItGLzrwlh9+fZrk6s2+uvIZN0jgg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=daOf9h0G; arc=none smtp.client-ip=192.198.163.18 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="daOf9h0G" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1783720492; x=1815256492; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=CRsufZHSl8mAGIVIzULD/lVBN6+M2i7HeN/b1zpdF34=; b=daOf9h0GyzJOgd64uaGW397DjniwjhLOYD4rspgGvrlv9krEJJuBmXFa bdX2NvlPpfuLsAwxvgavrMlIamu7O9z9l5cgPqRtgnfnvySAKs6N/0tNT PW5LpYkuOA4B36no21pJzjV3UiELdvCGUGiPyxdNavIOlkT4nt/K39Wes pdX/63vEiVHSP4RsxCi6HTvI4exrYGNYMWCMt7OdZ7hIIW+fAJ0N9ju79 o1mOg+3Y/b9fTpbEfofSNTmqLThl6oADPDmVgfx8rnE4UwuGQNbhLi2hD 2Q/Zm1tbnlO3FPO+quUoPPVqfq8IEgyStWNxVPN3ravN6f/wK5vuo7xl8 Q==; X-CSE-ConnectionGUID: OLulIMfJR6a6nMsNjBCG7A== X-CSE-MsgGUID: 5lk4ooeHQyeCjYxRfVv+nQ== X-IronPort-AV: E=McAfee;i="6800,10657,11841"; a="83543081" X-IronPort-AV: E=Sophos;i="6.25,154,1779174000"; d="scan'208";a="83543081" Received: from fmviesa003.fm.intel.com ([10.60.135.143]) by fmvoesa112.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Jul 2026 14:54:49 -0700 X-CSE-ConnectionGUID: 98yE1KLgQhu6BA+sLgJysw== X-CSE-MsgGUID: fIgRlXc3RXimCT2VNPf1kw== X-ExtLoop1: 1 Received: from gsse-cloud1.jf.intel.com ([10.54.39.91]) by fmviesa003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Jul 2026 14:54:49 -0700 From: Matthew Brost To: intel-xe@lists.freedesktop.org, dri-devel@lists.freedesktop.org Cc: Carlos Santa , Ryan Neph , Christian Koenig , Huang Rui , Matthew Auld , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , linux-kernel@vger.kernel.org, =?UTF-8?q?Thomas=20Hellstr=C3=B6m?= Subject: [PATCH v2 06/33] drm/ttm: Add fault injection for beneficial-order allocation failures Date: Fri, 10 Jul 2026 14:54:15 -0700 Message-Id: <20260710215442.2444235-7-matthew.brost@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260710215442.2444235-1-matthew.brost@intel.com> References: <20260710215442.2444235-1-matthew.brost@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add a beneficial_order_fault_inject debugfs fault attribute, mirroring backup_fault_inject, that forces allocation at (or above) the device's beneficial order to fail in __ttm_pool_alloc(). When triggered, both the pool take and the system page allocation are skipped for that order, so the allocation falls into the existing lower-the-order path that sets the TTM_TT_FLAG_BENEFICIAL_ORDER_FAILED tt page flag (and bails out with -ENOMEM for defrag moves). This lets the TTM_TT_FLAG_BENEFICIAL_ORDER_FAILED tracking and the driver-side defrag path be exercised deterministically, without having to drive the system into real memory fragmentation to provoke a sub-optimal backing. The knob is registered at /sys/kernel/debug/ttm/beneficial_order_fault_inject and compiles out when CONFIG_FAULT_INJECTION is disabled. Cc: Carlos Santa Cc: Ryan Neph Cc: Christian Koenig Cc: Huang Rui Cc: Matthew Auld Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Thomas Zimmermann Cc: David Airlie Cc: Simona Vetter Cc: dri-devel@lists.freedesktop.org Cc: linux-kernel@vger.kernel.org Cc: Thomas Hellström Assisted-by: GitHub_Copilot:claude-opus-4.8 Signed-off-by: Matthew Brost --- drivers/gpu/drm/ttm/ttm_pool.c | 35 ++++++++++++++++++++++++++++------ 1 file changed, 29 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c index 340855e9bcfe..34f533adb8eb 100644 --- a/drivers/gpu/drm/ttm/ttm_pool.c +++ b/drivers/gpu/drm/ttm/ttm_pool.c @@ -53,6 +53,7 @@ #ifdef CONFIG_FAULT_INJECTION #include static DECLARE_FAULT_ATTR(backup_fault_inject); +static DECLARE_FAULT_ATTR(beneficial_order_fault_inject); #else #define should_fail(...) false #endif @@ -812,21 +813,34 @@ struct ttm_pool_alloc_iter { unsigned int order; enum ttm_caching page_caching; bool allow_pools; + bool fail_beneficial; struct page *p; }; /* * Acquire a single page for the current order, leaving it in @it->p (NULL on - * failure). Tries a same-order pool page, then a fresh system allocation. + * failure). Tries a same-order pool page, then a fresh system allocation. Fault + * injection can force the beneficial-order paths to "fail". */ static void ttm_pool_iter_acquire_page(struct ttm_pool_alloc_iter *it) { struct ttm_pool_type *pt; - /* First, try to allocate a page from a pool if one exists. */ it->p = NULL; + + /* + * Fault injection: pretend allocation at (or above) the device's + * beneficial order failed, forcing a sub-optimal backing. Exercises the + * beneficial_order_failed tracking and the driver defrag path without + * driving the system into real fragmentation. + */ + it->fail_beneficial = IS_ENABLED(CONFIG_FAULT_INJECTION) && + it->beneficial_order && it->order >= it->beneficial_order && + should_fail(&beneficial_order_fault_inject, 1); + + /* First, try to allocate a page from a pool if one exists. */ pt = ttm_pool_select_type(it->pool, it->page_caching, it->order); - if (!it->p && pt && it->allow_pools) + if (!it->p && pt && it->allow_pools && !it->fail_beneficial) it->p = ttm_pool_type_take(pt, ttm_pool_nid(it->pool)); /* @@ -834,7 +848,7 @@ static void ttm_pool_iter_acquire_page(struct ttm_pool_alloc_iter *it) * this also disallows additional pool allocations using write-back * cached pools of the same order. */ - if (!it->p) { + if (!it->p && !it->fail_beneficial) { it->page_caching = ttm_cached; it->allow_pools = false; it->p = ttm_pool_alloc_page(it->pool, it->gfp_flags, it->order, @@ -851,6 +865,9 @@ static void ttm_pool_iter_acquire_page(struct ttm_pool_alloc_iter *it) */ static int ttm_pool_iter_lower_order(struct ttm_pool_alloc_iter *it) { + bool at_beneficial = it->beneficial_order && + it->order == it->beneficial_order; + if (!it->order) return -ENOMEM; @@ -860,13 +877,16 @@ static int ttm_pool_iter_lower_order(struct ttm_pool_alloc_iter *it) * pages. Record it so the driver can later try to defragment the object * back to beneficial order. */ - if (it->beneficial_order && it->order == it->beneficial_order) { + if (it->fail_beneficial || at_beneficial) { it->tt->page_flags |= TTM_TT_FLAG_BENEFICIAL_ORDER_FAILED; if (it->ctx->defrag) return -ENOMEM; } - it->order--; + if (it->fail_beneficial) + it->order = it->beneficial_order - 1; + else + it->order--; it->page_caching = it->tt->caching; it->allow_pools = true; @@ -1536,6 +1556,9 @@ int ttm_pool_mgr_init(unsigned long num_pages) #ifdef CONFIG_FAULT_INJECTION fault_create_debugfs_attr("backup_fault_inject", ttm_debugfs_root, &backup_fault_inject); + fault_create_debugfs_attr("beneficial_order_fault_inject", + ttm_debugfs_root, + &beneficial_order_fault_inject); #endif #endif -- 2.34.1