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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E5563C001DE for ; Tue, 25 Jul 2023 09:09:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230195AbjGYJJu (ORCPT ); Tue, 25 Jul 2023 05:09:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50982 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229656AbjGYJJt (ORCPT ); Tue, 25 Jul 2023 05:09:49 -0400 Received: from madras.collabora.co.uk (madras.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e5ab]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 36FEF9B; Tue, 25 Jul 2023 02:09:48 -0700 (PDT) Received: from [192.168.100.7] (unknown [59.103.217.18]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: usama.anjum) by madras.collabora.co.uk (Postfix) with ESMTPSA id 7AD6F6607108; Tue, 25 Jul 2023 10:09:39 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1690276186; bh=XdNAqD8pBtuejUuQFT+jmKzDVpGQZBU3/DTPb3ihEmo=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=d7hVqBt3iuMHzYWfjG0CGNHi2ClrCmnXnBTsfB/r7HruJrbnSCqcl0i0Tg7QTfYQ6 NEbT9Gf30FbGxTKFtJrrJQlSSubGDgkKQHQ+ORIjYELSwWMG2oVJnCUm62xTckCxFB jelQdGbUVo+0zxdWEwD895dvUagXZbyEbhEA3Aq6aEr0MVtd+tQ0D2fHTExwRtkTen wGVREO5J1I63LV0rUN4hVnwdt0kWyGDsnwbF8HM4sFeGVeFVwQzO9MYJU7epJWQan7 Q9Bz2C8Y6/lcexEifufO2KP+gsE8uaxCCE00xg2rI5uasR2VO6ibEn8PUYe9IU+BdT 1VecNbs2To1Ug== Message-ID: <1afedab8-5929-61e5-b0da-9c70dc01c254@collabora.com> Date: Tue, 25 Jul 2023 14:09:32 +0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Cc: Muhammad Usama Anjum , =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= , Andrei Vagin , Danylo Mocherniuk , Alex Sierra , Alexander Viro , Andrew Morton , Axel Rasmussen , Christian Brauner , Cyrill Gorcunov , Dan Williams , David Hildenbrand , Greg KH , "Gustavo A . R . Silva" , "Liam R . Howlett" , Matthew Wilcox , Mike Rapoport , Nadav Amit , Pasha Tatashin , Paul Gofman , Peter Xu , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , Yang Shi , Yun Zhou , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, kernel@collabora.com Subject: Re: [v2] fs/proc/task_mmu: Implement IOCTL for efficient page table scanning Content-Language: en-US To: =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= References: <20230713101415.108875-6-usama.anjum@collabora.com> <7eedf953-7cf6-c342-8fa8-b7626d69ab63@collabora.com> <382f4435-2088-08ce-20e9-bc1a15050861@collabora.com> <44eddc7d-fd68-1595-7e4f-e196abe37311@collabora.com> From: Muhammad Usama Anjum In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On 7/25/23 12:23 PM, Muhammad Usama Anjum wrote: > On 7/24/23 9:10 PM, Michał Mirosław wrote: > [...]>>>> @@ -2219,22 +2225,24 @@ static int pagemap_scan_get_args(struct > pm_scan_arg >>>>> *arg, >>>>> arg->category_anyof_mask | arg->return_mask) & ~PM_SCAN_CATEGORIES) >>>>> return -EINVAL; >>>>> >>>>> - start = untagged_addr((unsigned long)arg->start); >>>>> - end = untagged_addr((unsigned long)arg->end); >>>>> - vec = untagged_addr((unsigned long)arg->vec); >>>>> + arg->start = untagged_addr((unsigned long)arg->start); >>>>> + arg->end = untagged_addr((unsigned long)arg->end); >>>>> + arg->vec = untagged_addr((unsigned long)arg->vec); >>>> >>>> BTW, We should we keep the tag in args writeback(). >>> Sorry what? >>> After this function, the start, end and vec would be used. We need to make >>> sure that the address are untagged before that. >> >> We do write back the address the walk ended at to arg->start in >> userspace. This pointer I think needs the tag reconstructed so that >> retrying the ioctl() will be possible. > Even if we reconstruct the tag for end and vec, We need to update the start > address. Can we just put same tag as original start in it? I'm not sure. The special users would use tags. If they are using it, they'll just re-add the tag in next invocation. I think this implementation is correct. > -- BR, Muhammad Usama Anjum