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[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