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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8CFE3D111A8 for ; Mon, 1 Dec 2025 08:05:15 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 0D36F10E0E1; Mon, 1 Dec 2025 08:05:15 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=collabora.com header.i=@collabora.com header.b="l8LYok3j"; dkim-atps=neutral Received: from bali.collaboradmins.com (bali.collaboradmins.com [148.251.105.195]) by gabe.freedesktop.org (Postfix) with ESMTPS id 3E1E210E0E1; Mon, 1 Dec 2025 08:05:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1764576312; bh=AOGaPCVrzkgZmmb9BtWGyYN/DIDoq1iWanmV0V1M44s=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=l8LYok3jpLm4g5fxltRSyH6uFrGONRIfd8dZNss7W921eaCZVbddag1SUJJ9+x7Wd v4jor1LAPe/fKVE9AcxvzBGC2VwaE8g/VpjBxLKiQi5W0r8vZcWESYAYIHXKVIaGV4 FOCBkOSXwNk6ZibxuXsqbQ/F4eYg5pHmIjf3i9p6r5WX4iPhwO5WprDZEtBEtLU/OP ZDyOt/iNXXvL9teGdKTw8GJpWlCD1NnRePubQyLZJGvi7o8aa4MgYkPthTMYqmD4uL BTg5xy7sU5rxtxk6+cG3PqB7WTOB7An6zJT//b4QsD4O37HcF2ZtRPpKKOyhgMIysK VvT6wnLQQemZg== Received: from fedora (unknown [IPv6:2a01:e0a:2c:6930:d919:a6e:5ea1:8a9f]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (prime256v1) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bbrezillon) by bali.collaboradmins.com (Postfix) with ESMTPSA id 5A3C517E0020; Mon, 1 Dec 2025 09:05:11 +0100 (CET) Date: Mon, 1 Dec 2025 09:05:07 +0100 From: Boris Brezillon To: =?UTF-8?B?TG/Dr2M=?= Molinari Cc: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , Rob Herring , Steven Price , Liviu Dudau , Melissa Wen , =?UTF-8?B?TWHDrXJh?= Canal , Hugh Dickins , Baolin Wang , Andrew Morton , Al Viro , =?UTF-8?B?TWlrb8WCYWo=?= Wasiak , Christian Brauner , Nitin Gote , Andi Shyti , Jonathan Corbet , Christopher Healy , Matthew Wilcox , Bagas Sanjaya , 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: Re: [PATCH v10 01/10] drm/shmem-helper: Simplify page offset calculation in fault handler Message-ID: <20251201090507.1ee10c65@fedora> In-Reply-To: <20251128185252.3092-2-loic.molinari@collabora.com> References: <20251128185252.3092-1-loic.molinari@collabora.com> <20251128185252.3092-2-loic.molinari@collabora.com> Organization: Collabora X-Mailer: Claws Mail 4.3.1 (GTK 3.24.51; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Fri, 28 Nov 2025 19:52:43 +0100 Lo=C3=AFc Molinari wrote: > For a fault at address addr, the page offset is > page_offset =3D (vmf->address - vma->vm_start) >> PAGE_SHIFT > =3D ((addr & PAGE_MASK) - vma->vm_start) >> PAGE_SHIFT > =3D (addr - vma->vm_start) >> PAGE_SHIFT >=20 > Since the faulty logical page offset based on VMA is > vmf->pgoff =3D vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT) >=20 > We can slightly simplify the calculation using > page_offset =3D vmf->pgoff - vma->vm_pgoff >=20 > Signed-off-by: Lo=C3=AFc Molinari Reviewed-by: Boris Brezillon One nit below > --- > drivers/gpu/drm/drm_gem_shmem_helper.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) >=20 > diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm= _gem_shmem_helper.c > index dc94a27710e5..be89be1c804c 100644 > --- a/drivers/gpu/drm/drm_gem_shmem_helper.c > +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c > @@ -577,8 +577,8 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault= *vmf) > struct page *page; > pgoff_t page_offset; > =20 > - /* We don't use vmf->pgoff since that has the fake offset */ > - page_offset =3D (vmf->address - vma->vm_start) >> PAGE_SHIFT; > + /* Offset to faulty address in the VMA (without the fake offset). */ It's weird to say "without the fake offset" here, because IIUC, both vmf->pgoff and vma->vm_pgoff contain the fake offset. And that's fine, the problem really is when one of the subtraction operand is not relative to the fake offset. > + page_offset =3D vmf->pgoff - vma->vm_pgoff; > =20 > dma_resv_lock(shmem->base.resv, NULL); > =20