From nobody Mon Feb 9 00:27:26 2026 Received: from bali.collaboradmins.com (bali.collaboradmins.com [148.251.105.195]) (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 0A79B1547D2; Wed, 15 Oct 2025 15:30:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.251.105.195 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760542237; cv=none; b=uocceaw0zex7hRbOKQpLbRWbScDRItpCcKsjlZrReJNJfQRKEesLHkVHvNKglQcsKODFwBtuxCMGGLBY//4zIURDA34iGtTUn6gwacq4xGZrMI3hTVsb0bwnykiZPjuHphT6hLzpn5yzqzkflrm6f9SxFuJWFxl7DaLiaGRSWSs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760542237; c=relaxed/simple; bh=i4jm8rfdS6G2Q04+yn738KVCd/HzsGzB/QnSS+UslAY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=jqs5uAcZzjze364u9Kgegi+/3ptYtS+vH5ZIdaestm/aeWifpHZU/OF0EHmxfiSlg62HgS6AK5H6vF8bYOGk6rRtDpCdOtVQ2HqHM1JVtExgenXFhYjNG+IybEQSQy/qc1Mc0tpSGHwJZGrOaiLKi6HKhTbNLD6jrZgzNIz1U7Y= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b=bbJ9H8kS; arc=none smtp.client-ip=148.251.105.195 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b="bbJ9H8kS" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1760542233; bh=i4jm8rfdS6G2Q04+yn738KVCd/HzsGzB/QnSS+UslAY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bbJ9H8kSS1f9ZoeWKjtxRJDn57F4aP9klFG+XuHkXvOM8yZFcdQTWI5cb2BEuBEk1 gVlMJJSTxWdv7EeLK6TeJ7u5ga9M4xvTanGsth/ibKUIo0KZC3bn7JO+7mQYiswrYR pkac4KqbcFUdapTzUYAgNaWFReRqspgUU8FjvxSyQ5H14ybi4wPK/XEgakwCCCjVM4 Kj3PtLfZOyhbkx1CKLrHBeYNCKoCZCdQKzmNbkwp61DBH5Ok3vzetZkd8rGCiKiE0p inqYp/LBPgAunLivVYd7YRz17mgsyxLAww+B6EVZZ/EllLRF1uf5lGlsRpq8/qrnQ6 OtowYlUAfOltg== Received: from debian-rockchip-rock5b-rk3588.. (unknown [IPv6:2a01:e0a:5e3:6100:826d:bc07:e98c:84a]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: loicmolinari) by bali.collaboradmins.com (Postfix) with ESMTPSA id 7DF5917E055D; Wed, 15 Oct 2025 17:30:32 +0200 (CEST) From: =?UTF-8?q?Lo=C3=AFc=20Molinari?= To: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , Boris Brezillon , Rob Herring , Steven Price , Liviu Dudau , Melissa Wen , =?UTF-8?q?Ma=C3=ADra=20Canal?= , Hugh Dickins , Baolin Wang , Andrew Morton , =?UTF-8?q?Lo=C3=AFc=20Molinari?= , Al Viro , =?UTF-8?q?Miko=C5=82aj=20Wasiak?= , Christian Brauner , Nitin Gote , Andi Shyti , Jonathan Corbet , Christopher Healy , Matthew Wilcox , Bagas Sanjaya Cc: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, kernel@collabora.com Subject: [PATCH v4 03/13] drm/shmem-helper: Map huge pages in fault handlers Date: Wed, 15 Oct 2025 17:30:07 +0200 Message-ID: <20251015153018.43735-4-loic.molinari@collabora.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20251015153018.43735-1-loic.molinari@collabora.com> References: <20251015153018.43735-1-loic.molinari@collabora.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: quoted-printable Check whether the starting address in the fault-around handler or the faulty address in the fault handler is part of a huge page in order to attempt a PMD sized PFN insertion into the VMA. On builds with CONFIG_TRANSPARENT_HUGEPAGE enabled, if the mmap() user address is PMD size aligned, if the GEM object is backed by shmem buffers on mount points setting the 'huge=3D' option and if the shmem backing store manages to allocate a huge folio, CPU mapping would then benefit from significantly increased memcpy() performance. When these conditions are met on a system with 2 MiB huge pages, an aligned copy of 2 MiB would raise a single page fault instead of 4096. v4: - Implement map_pages instead of huge_fault Signed-off-by: Lo=C3=AFc Molinari --- drivers/gpu/drm/drm_gem_shmem_helper.c | 57 +++++++++++++++++++++----- 1 file changed, 46 insertions(+), 11 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_g= em_shmem_helper.c index e151262332f9..5d11bea573fe 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -580,6 +580,26 @@ static bool drm_gem_shmem_fault_is_valid(struct drm_ge= m_object *obj, return true; } =20 +static bool drm_gem_shmem_map_pmd(struct vm_fault *vmf, unsigned long addr, + struct page *page) +{ +#ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP + unsigned long pfn =3D page_to_pfn(page); + unsigned long paddr =3D pfn << PAGE_SHIFT; + bool aligned =3D (addr & ~PMD_MASK) =3D=3D (paddr & ~PMD_MASK); + + if (aligned && + pmd_none(*vmf->pmd) && + folio_test_pmd_mappable(page_folio(page))) { + pfn &=3D PMD_MASK >> PAGE_SHIFT; + if (vmf_insert_pfn_pmd(vmf, pfn, false) =3D=3D VM_FAULT_NOPAGE) + return true; + } +#endif + + return false; +} + static vm_fault_t drm_gem_shmem_map_pages(struct vm_fault *vmf, pgoff_t start_pgoff, pgoff_t end_pgoff) @@ -587,6 +607,7 @@ static vm_fault_t drm_gem_shmem_map_pages(struct vm_fau= lt *vmf, struct vm_area_struct *vma =3D vmf->vma; struct drm_gem_object *obj =3D vma->vm_private_data; struct drm_gem_shmem_object *shmem =3D to_drm_gem_shmem_obj(obj); + struct page **pages =3D shmem->pages; unsigned long addr, pfn; vm_fault_t ret; =20 @@ -598,15 +619,22 @@ static vm_fault_t drm_gem_shmem_map_pages(struct vm_f= ault *vmf, =20 if (unlikely(!drm_gem_shmem_fault_is_valid(obj, start_pgoff))) { ret =3D VM_FAULT_SIGBUS; - } else { - /* Map a range of pages around the faulty address. */ - do { - pfn =3D page_to_pfn(shmem->pages[start_pgoff]); - ret =3D vmf_insert_pfn(vma, addr, pfn); - addr +=3D PAGE_SIZE; - } while (++start_pgoff <=3D end_pgoff && ret =3D=3D VM_FAULT_NOPAGE); + goto out; } =20 + if (drm_gem_shmem_map_pmd(vmf, addr, pages[start_pgoff])) { + ret =3D VM_FAULT_NOPAGE; + goto out; + } + + /* Map a range of pages around the faulty address. */ + do { + pfn =3D page_to_pfn(pages[start_pgoff]); + ret =3D vmf_insert_pfn(vma, addr, pfn); + addr +=3D PAGE_SIZE; + } while (++start_pgoff <=3D end_pgoff && ret =3D=3D VM_FAULT_NOPAGE); + + out: dma_resv_unlock(shmem->base.resv); =20 return ret; @@ -617,8 +645,9 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *= vmf) struct vm_area_struct *vma =3D vmf->vma; struct drm_gem_object *obj =3D vma->vm_private_data; struct drm_gem_shmem_object *shmem =3D to_drm_gem_shmem_obj(obj); - struct page *page; + struct page **pages =3D shmem->pages; pgoff_t page_offset; + unsigned long pfn; vm_fault_t ret; =20 /* Offset to faulty address in the VMA (without the fake offset). */ @@ -628,12 +657,18 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault= *vmf) =20 if (unlikely(!drm_gem_shmem_fault_is_valid(obj, page_offset))) { ret =3D VM_FAULT_SIGBUS; - } else { - page =3D shmem->pages[page_offset]; + goto out; + } =20 - ret =3D vmf_insert_pfn(vma, vmf->address, page_to_pfn(page)); + if (drm_gem_shmem_map_pmd(vmf, vmf->address, pages[page_offset])) { + ret =3D VM_FAULT_NOPAGE; + goto out; } =20 + pfn =3D page_to_pfn(pages[page_offset]); + ret =3D vmf_insert_pfn(vma, vmf->address, pfn); + + out: dma_resv_unlock(shmem->base.resv); =20 return ret; --=20 2.47.3