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[87.19.108.254]) by smtp.gmail.com with ESMTPSA id y12-20020a5d470c000000b002c70ce264bfsm10238018wrq.76.2023.04.17.03.39.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Apr 2023 03:39:01 -0700 (PDT) From: "Fabio M. De Francesco" To: Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Daniel Vetter , Matt Roper , John Harrison , Daniele Ceraolo Spurio , Chris Wilson , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: "Fabio M. De Francesco" , Ira Weiny Subject: [PATCH v2 1/3] drm/i915: Replace kmap() with kmap_local_page() Date: Mon, 17 Apr 2023 12:38:52 +0200 Message-Id: <20230417103854.23333-2-fmdefrancesco@gmail.com> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230417103854.23333-1-fmdefrancesco@gmail.com> References: <20230417103854.23333-1-fmdefrancesco@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org kmap() has been deprecated in favor of kmap_local_page(). There are two main problems with kmap(): (1) It comes with an overhead as mapping space is restricted and protected by a global lock for synchronization and (2) it also requires global TLB invalidation when the kmap=E2=80=99s pool wraps and it might block when the mapping space is fully utilized until a slot becomes available. With kmap_local_page() the mappings are per thread, CPU local, can take page faults, and can be called from any context (including interrupts). It is faster than kmap() in kernels with HIGHMEM enabled. Furthermore, the tasks can be preempted and, when they are scheduled to run again, the kernel virtual addresses are restored and are still valid. Obviously, thread locality implies that the kernel voirtual addresses are valid only in the context of the callers. kmap_local_page() use in i915_gem.c doesn't break the above-mentioned constraint, so it should be preferred to kmap(). Therefore, replace kmap() with kmap_local_page() in i915_gem.c Suggested-by: Ira Weiny Signed-off-by: Fabio M. De Francesco --- drivers/gpu/drm/i915/i915_gem.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_ge= m.c index 35950fa91406..c35248555e42 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -212,14 +212,14 @@ shmem_pread(struct page *page, int offset, int len, c= har __user *user_data, char *vaddr; int ret; - vaddr =3D kmap(page); + vaddr =3D kmap_local_page(page); if (needs_clflush) drm_clflush_virt_range(vaddr + offset, len); ret =3D __copy_to_user(user_data, vaddr + offset, len); - kunmap(page); + kunmap_local(vaddr); return ret ? -EFAULT : 0; } @@ -643,7 +643,7 @@ shmem_pwrite(struct page *page, int offset, int len, ch= ar __user *user_data, char *vaddr; int ret; - vaddr =3D kmap(page); + vaddr =3D kmap_local_page(page); if (needs_clflush_before) drm_clflush_virt_range(vaddr + offset, len); @@ -652,7 +652,7 @@ shmem_pwrite(struct page *page, int offset, int len, ch= ar __user *user_data, if (!ret && needs_clflush_after) drm_clflush_virt_range(vaddr + offset, len); - kunmap(page); + kunmap_local(vaddr); return ret ? -EFAULT : 0; } -- 2.40.0 From nobody Wed Dec 17 21:12:51 2025 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 0FEF8C77B70 for ; Mon, 17 Apr 2023 10:41:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231234AbjDQKlH (ORCPT ); Mon, 17 Apr 2023 06:41:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41876 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230257AbjDQKk4 (ORCPT ); Mon, 17 Apr 2023 06:40:56 -0400 Received: from mail-wm1-x329.google.com (mail-wm1-x329.google.com [IPv6:2a00:1450:4864:20::329]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E9F565AF for ; Mon, 17 Apr 2023 03:40:09 -0700 (PDT) Received: by mail-wm1-x329.google.com with SMTP id he11-20020a05600c540b00b003ef6d684102so11584086wmb.3 for ; Mon, 17 Apr 2023 03:40:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1681727944; x=1684319944; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=dAW7sB6+Z5ZOltjkFBMt2NbhGjStc/CgCoci8oN9nks=; b=lk90wuKk7kR9IX6uMik68yOAyW5/zZmQWcphsp7dCp9z3gtp/owgQL9h2aAbLKBZl4 fCT8G5zvkCrwE8UQwr3TI2qV7TEBSeuZSe9ChabtOXCucPLOySit4w+Ukcnt1MR6xcJD RBcU0cLyIawG1B8WldS9XwJKzvAn1uvF3XJQUQD4rxY6QsnOGA8yokADx7cMlcSkaxFs 5+cWcTxbRQ//yFlyW01nwMQQHtlmblF6pwjWClW/urNU4TC+6JZnbE5L8Bg4kfHflzxL /4UrOEAQM7KKog1/7dO7jGRKmFaB5tY3maCKiDRQFq5G039Z4m4zDMRjCuuJMMI16nKs eHFQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1681727944; x=1684319944; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=dAW7sB6+Z5ZOltjkFBMt2NbhGjStc/CgCoci8oN9nks=; b=GGX0GN/bbEvuTs/BQ+LgMJ85EP11rMfTyWvaZUJT3qgmx4IVE76/2oy+fl6nWPcVtn ApZoLmwCYC/IxkW4hPABVNun+c1VftqtyBIxT+wCuXonxzs4lDAgKMyfanAiMZn0/iUL IAU+BekX+9cx0YLM/zBrdaqDzCt6NhaGyjItRcAuSBvj5aBD/H0B3kNubIg6q1lH+2NE w1M8C8poejuFLOxhjIsMoBjEy2QT1Parf1BBQiOyF1zWOQiKieyO6VSO7pp2kc8PEzYF gf3cB2pzDV/ySIX5NaZiUcT1UPzgrUO7P3R58gMs7OaQjJyo7PzEICbfbKTLCFhKvFcj RwXg== X-Gm-Message-State: AAQBX9d3UZlBbiKSBbCbJzujYk/hbk1ZUvt/V/90POeutcsUOwlIG8Cg 3I68MSBXJUPEJrcDQ6WMypk= X-Google-Smtp-Source: AKy350bqJ/bHsDjtLWvuVfbc6Uq/QInCoRKCm+KLyl/hHEccIaE3q+1++wO1znNLhcQOGVkqIM5BVw== X-Received: by 2002:a05:600c:4f46:b0:3f1:7443:6d6e with SMTP id m6-20020a05600c4f4600b003f174436d6emr1590807wmq.19.1681727943960; Mon, 17 Apr 2023 03:39:03 -0700 (PDT) Received: from localhost.localdomain (host-87-19-108-254.retail.telecomitalia.it. [87.19.108.254]) by smtp.gmail.com with ESMTPSA id y12-20020a5d470c000000b002c70ce264bfsm10238018wrq.76.2023.04.17.03.39.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Apr 2023 03:39:03 -0700 (PDT) From: "Fabio M. De Francesco" To: Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Daniel Vetter , Matt Roper , John Harrison , Daniele Ceraolo Spurio , Chris Wilson , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: "Fabio M. De Francesco" , Ira Weiny Subject: [PATCH v2 2/3] drm/i915/gt: Replace kmap() with kmap_local_page() Date: Mon, 17 Apr 2023 12:38:53 +0200 Message-Id: <20230417103854.23333-3-fmdefrancesco@gmail.com> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230417103854.23333-1-fmdefrancesco@gmail.com> References: <20230417103854.23333-1-fmdefrancesco@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org kmap() s been deprecated in favor of kmap_local_page(). There are two main problems with kmap(): (1) It comes with an overhead as mapping space is restricted and protected by a global lock for synchronization and (2) it also requires global TLB invalidation when the kmap=E2=80=99s pool wraps and it might block when the mapping space is fully utilized until a slot becomes available. With kmap_local_page() the mappings are per thread, CPU local, can take page faults, and can be called from any context (including interrupts). It is faster than kmap() in kernels with HIGHMEM enabled. Furthermore, the tasks can be preempted and, when they are scheduled to run again, the kernel virtual addresses are restored and are still valid. Obviously, thread locality implies that the kernel virtual addresses are only valid in the context of the callers. The use of kmap_local_page() in i915/gt doesn't break the above-mentioned constraint, so it should be preferred to kmap(). Therefore, replace kmap() with kmap_local_page() in i915/gt. Suggested-by: Ira Weiny Signed-off-by: Fabio M. De Francesco --- drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c | 4 ++-- drivers/gpu/drm/i915/gt/shmem_utils.c | 11 ++++------- 2 files changed, 6 insertions(+), 9 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c b/drivers/gpu/drm= /i915/gt/intel_ggtt_fencing.c index 37d0b0fe791d..89295c6921d6 100644 --- a/drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c +++ b/drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c @@ -749,7 +749,7 @@ static void swizzle_page(struct page *page) char *vaddr; int i; - vaddr =3D kmap(page); + vaddr =3D kmap_local_page(page); for (i =3D 0; i < PAGE_SIZE; i +=3D 128) { memcpy(temp, &vaddr[i], 64); @@ -757,7 +757,7 @@ static void swizzle_page(struct page *page) memcpy(&vaddr[i + 64], temp, 64); } - kunmap(page); + kunmap_local(vaddr); } /** diff --git a/drivers/gpu/drm/i915/gt/shmem_utils.c b/drivers/gpu/drm/i915/g= t/shmem_utils.c index 449c9ed44382..be809839a241 100644 --- a/drivers/gpu/drm/i915/gt/shmem_utils.c +++ b/drivers/gpu/drm/i915/gt/shmem_utils.c @@ -101,22 +101,19 @@ static int __shmem_rw(struct file *file, loff_t off, unsigned int this =3D min_t(size_t, PAGE_SIZE - offset_in_page(off), len); struct page *page; - void *vaddr; page =3D shmem_read_mapping_page_gfp(file->f_mapping, pfn, GFP_KERNEL); if (IS_ERR(page)) return PTR_ERR(page); - vaddr =3D kmap(page); if (write) { - memcpy(vaddr + offset_in_page(off), ptr, this); + memcpy_to_page(page, offset_in_page(off), ptr, this); set_page_dirty(page); } else { - memcpy(ptr, vaddr + offset_in_page(off), this); + memcpy_from_page(ptr, page, offset_in_page(off), this); } mark_page_accessed(page); - kunmap(page); put_page(page); len -=3D this; @@ -143,11 +140,11 @@ int shmem_read_to_iosys_map(struct file *file, loff_t= off, if (IS_ERR(page)) return PTR_ERR(page); - vaddr =3D kmap(page); + vaddr =3D kmap_local_page(page); iosys_map_memcpy_to(map, map_off, vaddr + offset_in_page(off), this); mark_page_accessed(page); - kunmap(page); + kunmap_local(vaddr); put_page(page); len -=3D this; -- 2.40.0 From nobody Wed Dec 17 21:12:51 2025 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 19B8FC77B76 for ; Mon, 17 Apr 2023 10:41:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230476AbjDQKlD (ORCPT ); Mon, 17 Apr 2023 06:41:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41910 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230490AbjDQKk5 (ORCPT ); Mon, 17 Apr 2023 06:40:57 -0400 Received: from mail-wm1-x329.google.com (mail-wm1-x329.google.com [IPv6:2a00:1450:4864:20::329]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7E2576EBF for ; Mon, 17 Apr 2023 03:40:09 -0700 (PDT) Received: by mail-wm1-x329.google.com with SMTP id 5b1f17b1804b1-3f16ecaadd1so11692205e9.1 for ; Mon, 17 Apr 2023 03:40:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1681727946; x=1684319946; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=cH79Swn8ZRJ2/YarOj91Bz0xxg30p0nVIyjLTbfZHEk=; b=YRKjuLMhTl40C+QqFYNyd1bRihczrfYWx/yGU36IRsJfmSPwWm5zftNVBsPia6yv+S Zxqe6js3OrRVHvL9eVEwsHAVrpNhJPpvZcA3/CuoUjouJePIvyzvpsD+QqepRoAlloZ/ 0fsrKdoUG/TsMKLWUBTOHqggXyBAQ2C+BlCWcOm9TvmHiaIgIBq5KhCWjFeagOpEmB8d 1DAQ0WsJbDJw9QEjshxivpMLqq89xEmLpV7P0ecn/QKP2xODoAfG9PcVZbGxJetEzBPJ tD5YqlokKpW5QqC7IQ0a6OqDD1KDVY5I3WNXvmUYrxVtT80Kmg/URg+3ZpE9rLMH6zR0 2NkA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1681727946; x=1684319946; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=cH79Swn8ZRJ2/YarOj91Bz0xxg30p0nVIyjLTbfZHEk=; b=Iu8XvljOAjUbj48L0H5aC9fjQ4BVI/jq/utLLJmTi1Oq4ULnErhb2U4Sm8D4IzhSrS 8gqnjuXv1p1eEmtoDq6jaPz1mUC9CjYfycoBtK8NaT2DEf0DABKn/bJzHEjIRY51r3c7 xtlXdyeCY4OMuP2DTl1Gwyq5ZfTqAgypoUTF8jlnJ98s3zf3vXCdFmcLcOKvplj2IWyp gu6+73oJZ9Mi5BPkGOD8i6goagzMPFwV8UFgsDY9238AH5Z/h9mVIR8p2+6rwWDGImpC Kuh+dBDNdTzzK2K3LHqwOlBw7LjQoLniAxBi81r8aVC4xopoke81Uvaw4RGSYKZJoTZz woiw== X-Gm-Message-State: AAQBX9dCA6r2f3A0osGKfBLhR0jdEnXd5345nG90mbodnFv5iJ3GrRz8 O9fBj06k/oM+POGlzYA3DVU= X-Google-Smtp-Source: AKy350ZHLsYNFXN5GyVB3dvmvIOZLfVbmy328/EyKvOC+gnAZGSMikYnaDOJgYq7gQ7O8a2gX7ryOA== X-Received: by 2002:adf:d085:0:b0:2fa:88f2:b04c with SMTP id y5-20020adfd085000000b002fa88f2b04cmr1956315wrh.20.1681727945938; Mon, 17 Apr 2023 03:39:05 -0700 (PDT) Received: from localhost.localdomain (host-87-19-108-254.retail.telecomitalia.it. [87.19.108.254]) by smtp.gmail.com with ESMTPSA id y12-20020a5d470c000000b002c70ce264bfsm10238018wrq.76.2023.04.17.03.39.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Apr 2023 03:39:05 -0700 (PDT) From: "Fabio M. De Francesco" To: Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Daniel Vetter , Matt Roper , John Harrison , Daniele Ceraolo Spurio , Chris Wilson , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: "Fabio M. De Francesco" , Ira Weiny Subject: [PATCH v2 3/3] drm/i915/gem: Replace kmap() with kmap_local_page() Date: Mon, 17 Apr 2023 12:38:54 +0200 Message-Id: <20230417103854.23333-4-fmdefrancesco@gmail.com> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230417103854.23333-1-fmdefrancesco@gmail.com> References: <20230417103854.23333-1-fmdefrancesco@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org kmap() s been deprecated in favor of kmap_local_page(). There are two main problems with kmap(): (1) It comes with an overhead as mapping space is restricted and protected by a global lock for synchronization and (2) it also requires global TLB invalidation when the kmap=E2=80=99s pool wraps and it might block when the mapping space is fully utilized until a slot becomes available. With kmap_local_page() the mappings are per thread, CPU local, can take page faults, and can be called from any context (including interrupts). It is faster than kmap() in kernels with HIGHMEM enabled. Furthermore, the tasks can be preempted and, when they are scheduled to run again, the kernel virtual addresses are restored and are still valid. Obviously, thread locality implies that the kernel virtual addresses are only valid in the context of the callers. The kmap_local_page() use in i915/gem doesn't break the above-mentioned constraint, so it should be preferred to kmap(). Therefore, replace kmap() with kmap_local_page() in i915/gem and use memcpy_to_page() where it is possible to avoid the open coding of mapping + memcpy() + un-mapping. Suggested-by: Ira Weiny Signed-off-by: Fabio M. De Francesco --- drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 6 ++---- drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c | 8 ++++---- 2 files changed, 6 insertions(+), 8 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i9= 15/gem/i915_gem_shmem.c index 37d1efcd3ca6..8856a6409e83 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c @@ -657,16 +657,14 @@ i915_gem_object_create_shmem_from_data(struct drm_i91= 5_private *dev_priv, do { unsigned int len =3D min_t(typeof(size), size, PAGE_SIZE); struct page *page; - void *pgdata, *vaddr; + void *pgdata; err =3D aops->write_begin(file, file->f_mapping, offset, len, &page, &pgdata); if (err < 0) goto fail; - vaddr =3D kmap(page); - memcpy(vaddr, data, len); - kunmap(page); + memcpy_to_page(page, 0, data, len); err =3D aops->write_end(file, file->f_mapping, offset, len, len, page, pgdata); diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c b/drivers/g= pu/drm/i915/gem/selftests/i915_gem_mman.c index 56279908ed30..5fd9e1ee2340 100644 --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c @@ -155,7 +155,7 @@ static int check_partial_mapping(struct drm_i915_gem_ob= ject *obj, intel_gt_flush_ggtt_writes(to_gt(i915)); p =3D i915_gem_object_get_page(obj, offset >> PAGE_SHIFT); - cpu =3D kmap(p) + offset_in_page(offset); + cpu =3D kmap_local_page(p) + offset_in_page(offset); drm_clflush_virt_range(cpu, sizeof(*cpu)); if (*cpu !=3D (u32)page) { pr_err("Partial view for %lu [%u] (offset=3D%llu, size=3D%u [%llu, row s= ize %u], fence=3D%d, tiling=3D%d, stride=3D%d) misalignment, expected write= to page (%lu + %u [0x%lx]) of 0x%x, found 0x%x\n", @@ -173,7 +173,7 @@ static int check_partial_mapping(struct drm_i915_gem_ob= ject *obj, } *cpu =3D 0; drm_clflush_virt_range(cpu, sizeof(*cpu)); - kunmap(p); + kunmap_local(cpu); out: i915_gem_object_lock(obj, NULL); @@ -251,7 +251,7 @@ static int check_partial_mappings(struct drm_i915_gem_o= bject *obj, intel_gt_flush_ggtt_writes(to_gt(i915)); p =3D i915_gem_object_get_page(obj, offset >> PAGE_SHIFT); - cpu =3D kmap(p) + offset_in_page(offset); + cpu =3D kmap_local_page(p) + offset_in_page(offset); drm_clflush_virt_range(cpu, sizeof(*cpu)); if (*cpu !=3D (u32)page) { pr_err("Partial view for %lu [%u] (offset=3D%llu, size=3D%u [%llu, row = size %u], fence=3D%d, tiling=3D%d, stride=3D%d) misalignment, expected writ= e to page (%lu + %u [0x%lx]) of 0x%x, found 0x%x\n", @@ -269,7 +269,7 @@ static int check_partial_mappings(struct drm_i915_gem_o= bject *obj, } *cpu =3D 0; drm_clflush_virt_range(cpu, sizeof(*cpu)); - kunmap(p); + kunmap_local(cpu); if (err) return err; -- 2.40.0