From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3378DC19F2B for ; Fri, 29 Jul 2022 07:04:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234241AbiG2HED (ORCPT ); Fri, 29 Jul 2022 03:04:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50314 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233934AbiG2HEB (ORCPT ); Fri, 29 Jul 2022 03:04:01 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9D4B276952; Fri, 29 Jul 2022 00:04:00 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 39CD861A2B; Fri, 29 Jul 2022 07:04:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6A132C433B5; Fri, 29 Jul 2022 07:03:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1659078239; bh=2pBgez34jdxSq2XeGH8AFY1z97ZArOQJw9kuBPer8g8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qL9ZvuzdzoFSyPKBkfMxxITJ1fiVmiBoVdwUJU/9ZH1OijAVuluh6OMlVqJvZRIZk fDmBx0nBO1BzLQdzFk2xG2Q15rXLsHsafrxLWUshfDK7UHnOJQkyp/abKVFXttPuW6 XgY2pDU5+desMxhtOIMzG9dcs7NZ8uLI1NsxwSADZEC8+sMA3tFJC0zGRK/wLO1cc6 d5udp+mAY+bNf7Up4reFe6zpCBurO5ibi/2i6ghxxewOmqF6gZRUGBRge2a9wcDMbH Yiu9peycpeYmcS6hkh9N5dNO18zdLcJ7nBbYOa107ACD8K9RX+Fus0surt+4c+ShLf thoMgVLtW+KyA== Received: from mchehab by mail.kernel.org with local (Exim 4.95) (envelope-from ) id 1oHK2P-005nBw-3O; Fri, 29 Jul 2022 09:03:57 +0200 From: Mauro Carvalho Chehab Cc: Mauro Carvalho Chehab , Chris Wilson , Daniel Vetter , David Airlie , Jani Nikula , Jonathan Corbet , Joonas Lahtinen , Maarten Lankhorst , Maxime Ripard , Rodrigo Vivi , Thomas Zimmermann , Tvrtko Ursulin , dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 2/2] drm/i915/gt: document TLB cache invalidation functions Date: Fri, 29 Jul 2022 09:03:55 +0200 Message-Id: X-Mailer: git-send-email 2.36.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit To: unlisted-recipients:; (no To-header on input) Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Add a description for the TLB cache invalidation algorithm and for the related kAPI functions. Signed-off-by: Mauro Carvalho Chehab --- To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover. See [PATCH v2 0/2] at: https://lore.kernel.org/all/cover.1659077372.git.mchehab@kernel.org/ Documentation/gpu/i915.rst | 7 ++ drivers/gpu/drm/i915/gt/intel_tlb.c | 25 +++++++ drivers/gpu/drm/i915/gt/intel_tlb.h | 101 ++++++++++++++++++++++++++++ 3 files changed, 133 insertions(+) diff --git a/Documentation/gpu/i915.rst b/Documentation/gpu/i915.rst index 4e59db1cfb00..46911fdd79e8 100644 --- a/Documentation/gpu/i915.rst +++ b/Documentation/gpu/i915.rst @@ -58,6 +58,13 @@ Intel GVT-g Host Support(vGPU device model) .. kernel-doc:: drivers/gpu/drm/i915/intel_gvt.c :internal: +TLB cache invalidation +---------------------- + +.. kernel-doc:: drivers/gpu/drm/i915/gt/intel_tlb.h + +.. kernel-doc:: drivers/gpu/drm/i915/gt/intel_tlb.c + Workarounds ----------- diff --git a/drivers/gpu/drm/i915/gt/intel_tlb.c b/drivers/gpu/drm/i915/gt/intel_tlb.c index af8cae979489..4873b7ecc015 100644 --- a/drivers/gpu/drm/i915/gt/intel_tlb.c +++ b/drivers/gpu/drm/i915/gt/intel_tlb.c @@ -145,6 +145,18 @@ static void mmio_invalidate_full(struct intel_gt *gt) intel_uncore_forcewake_put_delayed(uncore, FORCEWAKE_ALL); } +/** + * intel_gt_invalidate_tlb_full - do full TLB cache invalidation + * @gt: GT structure + * @seqno: sequence number + * + * Do a full TLB cache invalidation if the @seqno is bigger than the last + * full TLB cache invalidation. + * + * Note: + * The TLB cache invalidation logic depends on GEN-specific registers. + * It currently supports MMIO-based TLB flush for GEN8 to GEN12. + */ void intel_gt_invalidate_tlb_full(struct intel_gt *gt, u32 seqno) { intel_wakeref_t wakeref; @@ -171,12 +183,25 @@ void intel_gt_invalidate_tlb_full(struct intel_gt *gt, u32 seqno) } } +/** + * intel_gt_init_tlb - initialize TLB-specific vars + * @gt: GT structure + * + * TLB cache invalidation logic internally uses some resources that require + * initialization. Should be called before doing any TLB cache invalidation. + */ void intel_gt_init_tlb(struct intel_gt *gt) { mutex_init(>->tlb.invalidate_lock); seqcount_mutex_init(>->tlb.seqno, >->tlb.invalidate_lock); } +/** + * intel_gt_fini_tlb - initialize TLB-specific vars + * @gt: GT structure + * + * Frees any resources needed by TLB cache invalidation logic. + */ void intel_gt_fini_tlb(struct intel_gt *gt) { mutex_destroy(>->tlb.invalidate_lock); diff --git a/drivers/gpu/drm/i915/gt/intel_tlb.h b/drivers/gpu/drm/i915/gt/intel_tlb.h index 46ce25bf5afe..dca70c33bd61 100644 --- a/drivers/gpu/drm/i915/gt/intel_tlb.h +++ b/drivers/gpu/drm/i915/gt/intel_tlb.h @@ -11,16 +11,117 @@ #include "intel_gt_types.h" +/** + * DOC: TLB cache invalidation logic + * + * The way the current algorithm works is that a struct drm_i915_gem_object can + * be created on any order. At unbind/evict time, the object is warranted that + * it won't be used anymore. So, a sequence number provided by + * intel_gt_next_invalidate_tlb_full() is stored on it. This can happen either + * at __vma_put_pages() - for VMA sync unbind, or at ppgtt_unbind_vma() - for + * VMA async VMA bind. + * + * At __i915_gem_object_unset_pages(), intel_gt_invalidate_tlb_full() is called, + * where it checks if the sequence number of the object was already invalidated + * or not. If not, it flushes the TLB and increments the sequence number:: + * + * void intel_gt_invalidate_tlb_full(struct intel_gt *gt, u32 seqno) + * { + * ... + * with_intel_gt_pm_if_awake(gt, wakeref) { + * mutex_lock(>->tlb.invalidate_lock); + * if (tlb_seqno_passed(gt, seqno)) + * goto unlock; + * + * // Some code to do TLB invalidation + * ... + * + * write_seqcount_invalidate(>->tlb.seqno); // increment seqno + * mutex_lock(>->tlb.invalidate_lock); + * } + * + * So, let's say the current seqno is 2 and 3 new objects were created, + * on this order:: + * + * obj1 + * obj2 + * obj3 + * + * They can be unbind/evict on a different order. At unbind/evict time, + * the mm.tlb will be stamped with the sequence number, using the number + * from the last TLB flush, plus 1. + * + * Different threads may be used on unbind/evict and/or unset pages. + * As the logic at void intel_gt_invalidate_tlb_full() is protected by a mutex, + * for simplicity, let's consider just two threads: + * + * +-------------------+-------------------------+---------------------------------+ + * | sequence number | Thread 0 | Thread 1 + + * +===================+=========================+=================================+ + * | seqno=2 | | | + * | +-------------------------+---------------------------------+ + * | | unbind/evict obj3. | | + * | | | | + * | | obj3.mm.tlb = seqno | 1 | | + * | | // obj3.mm.tlb = 3 | | + * | +-------------------------+---------------------------------+ + * | | unbind/evict obj1. | | + * | | | | + * | | obj1.mm.tlb = seqno | 1 | | + * | | // obj1.mm.tlb = 3 | | + * | +-------------------------+---------------------------------+ + * | | | __i915_gem_object_unset_pages() | + * | | | called for obj3 => TLB flush | + * | | | invalidating both obj1 and obj2.| + * | | | | + * | | | seqno += 2 | + * +-------------------+-------------------------+---------------------------------+ + * | seqno=4 | | | + * | +-------------------------+---------------------------------+ + * | | unbind/evict obj2. | | + * | | | | + * | | obj2.mm.tlb = seqno | 1 | | + * | | // obj2.mm.tlb = 5 | | + * | +-------------------------+---------------------------------+ + * | | | __i915_gem_object_unset_pages() | + * | | | called for obj1, don't flush | + * | | | as past flush invalidated obj1. | + * | +-------------------------+---------------------------------+ + * | | | __i915_gem_object_unset_pages() | + * | | | called for obj2 => TLB flush. | + * | | | invalidating obj2. | + * | | | | + * | | | seqno += 2 | + * +-------------------+-------------------------+---------------------------------+ + * | seqno=6 | | | + * +-------------------+-------------------------+---------------------------------+ + */ + void intel_gt_invalidate_tlb_full(struct intel_gt *gt, u32 seqno); void intel_gt_init_tlb(struct intel_gt *gt); void intel_gt_fini_tlb(struct intel_gt *gt); +/** + * intel_gt_tlb_seqno - Returns the current TLB invlidation sequence number + * + * @gt: GT structure + * + * There's no need to lock while calling it, as seqprop_sequence is thread-safe + */ static inline u32 intel_gt_tlb_seqno(const struct intel_gt *gt) { return seqprop_sequence(>->tlb.seqno); } +/** + * intel_gt_next_invalidate_tlb_full - Returns the next TLB full invalidation + * sequence number + * + * @gt: GT structure + * + * There's no need to lock while calling it, as seqprop_sequence is thread-safe + */ static inline u32 intel_gt_next_invalidate_tlb_full(const struct intel_gt *gt) { return intel_gt_tlb_seqno(gt) | 1; -- 2.36.1