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[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