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 X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CF16DC433DB for ; Thu, 11 Feb 2021 09:49:12 +0000 (UTC) Received: from ml01.01.org (ml01.01.org [198.145.21.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7CA1D64E8B for ; Thu, 11 Feb 2021 09:49:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7CA1D64E8B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvdimm-bounces@lists.01.org Received: from ml01.vlan13.01.org (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id 0F425100EA906; Thu, 11 Feb 2021 01:49:12 -0800 (PST) Received-SPF: Pass (mailfrom) identity=mailfrom; client-ip=216.205.24.124; helo=us-smtp-delivery-124.mimecast.com; envelope-from=david@redhat.com; receiver= Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 0D628100EAB0D for ; Thu, 11 Feb 2021 01:49:08 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613036947; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=D4KClAbW7qAjd5KF/8/23pSoF5vXBE09nxYc8TlmEUM=; b=Wvdx4T0etpdPbxWRf+PxEFJXyobCquw7Ia8NzvSSWzmUeffoQFWCwdClzG+m2Hkk8SGnwz YemrIMC0OdkIuCDMBpWRJZLYEyOEpk0bZYvgjNDOCVi2cH9z7BygdvvfF0ff+TP6/Zp8DF XksTP0UZovQLIQrBYO+RF7TlE+rTDvQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-249-9tsn6XZgPY-p0wHYN_-nmw-1; Thu, 11 Feb 2021 04:49:03 -0500 X-MC-Unique: 9tsn6XZgPY-p0wHYN_-nmw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6F49280364D; Thu, 11 Feb 2021 09:48:58 +0000 (UTC) Received: from [10.36.114.52] (ovpn-114-52.ams2.redhat.com [10.36.114.52]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4AE5010016F4; Thu, 11 Feb 2021 09:48:49 +0000 (UTC) To: Michal Hocko References: <20210208084920.2884-1-rppt@kernel.org> <20210208084920.2884-8-rppt@kernel.org> <20210208212605.GX242749@kernel.org> <20210209090938.GP299309@linux.ibm.com> <20210211071319.GF242749@kernel.org> <0d66baec-1898-987b-7eaf-68a015c027ff@redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Subject: Re: [PATCH v17 07/10] mm: introduce memfd_secret system call to create "secret" memory areas Message-ID: <367808fc-8f5c-10a4-fc0b-a71df616dfce@redhat.com> Date: Thu, 11 Feb 2021 10:48:48 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Message-ID-Hash: VKWTVFK65WLXE43IQSUFOHY5FMKNQVPF X-Message-ID-Hash: VKWTVFK65WLXE43IQSUFOHY5FMKNQVPF X-MailFrom: david@redhat.com X-Mailman-Rule-Hits: nonmember-moderation X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation CC: Mike Rapoport , Mike Rapoport , Andrew Morton , Alexander Viro , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Christopher Lameter , Dave Hansen , Elena Reshetova , "H. Peter Anvin" , Ingo Molnar , James Bottomley , "Kirill A. Shutemov" , Matthew Wilcox , Mark Rutland , Michael Kerrisk , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , Rick Edgecombe , Roman Gushchin , Shakeel Butt , Shuah Khan , Thomas Gleixner , Tycho Ander sen , Will Deacon , linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-nvdimm@lists.01.org, linux-riscv@lists.infradead.org, x86@kernel.org, Hagen Paul Pfeifer , Palmer Dabbelt X-Mailman-Version: 3.1.1 Precedence: list List-Id: "Linux-nvdimm developer list." Archived-At: List-Archive: List-Help: List-Post: List-Subscribe: List-Unsubscribe: Content-Type: text/plain; charset="us-ascii"; format="flowed" Content-Transfer-Encoding: 7bit >> Some random thoughts regarding files. >> >> What is the page size of secretmem memory? Sometimes we use huge pages, >> sometimes we fallback to 4k pages. So I assume huge pages in general? > > Unless there is an explicit request for hugetlb I would say the page > size is not really important like for any other fds. Huge pages can be > used transparently. If everything is currently allocated/mapped on PTE granularity, then yes I agree. I remember previous versions used to "pool 2MB pages", which might have been problematic (thus, my concerns regarding mmap() etc.). If that part is now gone, good! > >> What are semantics of MADV()/FALLOCATE() etc on such files? > > I would expect the same semantic as regular shmem (memfd_create) except > the memory doesn't have _any_ backing storage which makes it > unevictable. So the reclaim related madv won't work but there shouldn't > be any real reason why e.g. MADV_DONTNEED, WILLNEED, DONT_FORK and > others don't work. Agreed if we don't have hugepage semantics. >> Is userfaultfd() properly fenced? Or does it even work (doubt)? >> >> How does it behave if I mmap(FIXED) something in between? >> In which granularity can I do that (->page-size?)? > > Again, nothing really exceptional here. This is a mapping like any > other from address space manipulation POV. Agreed with the PTE mapping approach. > >> What are other granularity restrictions (->page size)? >> >> Don't want to open a big discussion here, just some random thoughts. >> Maybe it has all been already figured out and most of the answers >> above are "Fails with -EINVAL". > > I think that the behavior should be really in sync with shmem semantic > as much as possible. Most operations should simply work with an > aditional direct map manipulation. There is no real reason to be > special. Some functionality might be missing, e.g. hugetlb support but > that has been traditionally added on top of shmem interface so nothing > really new here. Agreed! -- Thanks, David / dhildenb _______________________________________________ Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org To unsubscribe send an email to linux-nvdimm-leave@lists.01.org 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 X-Spam-Level: X-Spam-Status: No, score=-7.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5DC83C433E6 for ; Thu, 11 Feb 2021 09:54:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1A2F064E95 for ; Thu, 11 Feb 2021 09:54:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229923AbhBKJyP (ORCPT ); Thu, 11 Feb 2021 04:54:15 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:40921 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229963AbhBKJum (ORCPT ); Thu, 11 Feb 2021 04:50:42 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613036945; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=D4KClAbW7qAjd5KF/8/23pSoF5vXBE09nxYc8TlmEUM=; b=focAmQ/v8mp0bRxPmYQH1aPf4vHVEJrUl0tFegTzn3OuEeRsnJkCwn+dgcXnqGJA3N/BP0 4pXY84+aN1SfWXv1q7vk0Ty13ZDRosTJcP6E9D0Wd4WxLIGg4iRpWx0RjT4NIlSthi0eu4 Z/ms+V+Ia1l0JT+rsoxNXnWVhhoB53M= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-249-9tsn6XZgPY-p0wHYN_-nmw-1; Thu, 11 Feb 2021 04:49:03 -0500 X-MC-Unique: 9tsn6XZgPY-p0wHYN_-nmw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6F49280364D; Thu, 11 Feb 2021 09:48:58 +0000 (UTC) Received: from [10.36.114.52] (ovpn-114-52.ams2.redhat.com [10.36.114.52]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4AE5010016F4; Thu, 11 Feb 2021 09:48:49 +0000 (UTC) To: Michal Hocko Cc: Mike Rapoport , Mike Rapoport , Andrew Morton , Alexander Viro , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Christopher Lameter , Dan Williams , Dave Hansen , Elena Reshetova , "H. Peter Anvin" , Ingo Molnar , James Bottomley , "Kirill A. Shutemov" , Matthew Wilcox , Mark Rutland , Michael Kerrisk , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , Rick Edgecombe , Roman Gushchin , Shakeel Butt , Shuah Khan , Thomas Gleixner , Tycho Andersen , Will Deacon , linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-nvdimm@lists.01.org, linux-riscv@lists.infradead.org, x86@kernel.org, Hagen Paul Pfeifer , Palmer Dabbelt References: <20210208084920.2884-1-rppt@kernel.org> <20210208084920.2884-8-rppt@kernel.org> <20210208212605.GX242749@kernel.org> <20210209090938.GP299309@linux.ibm.com> <20210211071319.GF242749@kernel.org> <0d66baec-1898-987b-7eaf-68a015c027ff@redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Subject: Re: [PATCH v17 07/10] mm: introduce memfd_secret system call to create "secret" memory areas Message-ID: <367808fc-8f5c-10a4-fc0b-a71df616dfce@redhat.com> Date: Thu, 11 Feb 2021 10:48:48 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >> Some random thoughts regarding files. >> >> What is the page size of secretmem memory? Sometimes we use huge pages, >> sometimes we fallback to 4k pages. So I assume huge pages in general? > > Unless there is an explicit request for hugetlb I would say the page > size is not really important like for any other fds. Huge pages can be > used transparently. If everything is currently allocated/mapped on PTE granularity, then yes I agree. I remember previous versions used to "pool 2MB pages", which might have been problematic (thus, my concerns regarding mmap() etc.). If that part is now gone, good! > >> What are semantics of MADV()/FALLOCATE() etc on such files? > > I would expect the same semantic as regular shmem (memfd_create) except > the memory doesn't have _any_ backing storage which makes it > unevictable. So the reclaim related madv won't work but there shouldn't > be any real reason why e.g. MADV_DONTNEED, WILLNEED, DONT_FORK and > others don't work. Agreed if we don't have hugepage semantics. >> Is userfaultfd() properly fenced? Or does it even work (doubt)? >> >> How does it behave if I mmap(FIXED) something in between? >> In which granularity can I do that (->page-size?)? > > Again, nothing really exceptional here. This is a mapping like any > other from address space manipulation POV. Agreed with the PTE mapping approach. > >> What are other granularity restrictions (->page size)? >> >> Don't want to open a big discussion here, just some random thoughts. >> Maybe it has all been already figured out and most of the answers >> above are "Fails with -EINVAL". > > I think that the behavior should be really in sync with shmem semantic > as much as possible. Most operations should simply work with an > aditional direct map manipulation. There is no real reason to be > special. Some functionality might be missing, e.g. hugetlb support but > that has been traditionally added on top of shmem interface so nothing > really new here. Agreed! -- Thanks, David / dhildenb 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 X-Spam-Level: X-Spam-Status: No, score=-5.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C90BCC433DB for ; Thu, 11 Feb 2021 09:49:23 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7528064E92 for ; Thu, 11 Feb 2021 09:49:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7528064E92 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:Subject: From:References:To:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=b66N7wSgUnB5Z0wsY06Sr9hnQBY5hzetmeWWocypcEU=; b=SoE/mzv0rQmrm90wLr6LRdJZH IZnazzNa5nSSWWcj2gCxkmTre5gSFMFBajWaUIsZG/VfpAajWTczPV2qxg2SXPXEpd0UTR/eQH2WS W/sMJFi3qpFoW3JQQV2Hg/5KIQoTdP6TWw8od8so3LeaS5Mk5m6NuTl2WfiJzyMDpQ3KW3ykd1F5J xRQdZK/zL2YB1ZDCIkOG/pbhrbfcGXsGZBbII6ykbTiLIwBeuNk5WTV5B7QZG2ACrvkW4Lw1/vDrd 459UVFMytj0qv5AMtYAV76Bo52Fk6NZt/zk0a1p9x+bymtzJjsWnV4FLQhUNcWLuD3aKKs9MI1ZYw eKfURn3+Q==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1lA8b4-00081z-Oi; Thu, 11 Feb 2021 09:49:14 +0000 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1lA8b1-000803-7i for linux-riscv@lists.infradead.org; Thu, 11 Feb 2021 09:49:12 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613036947; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=D4KClAbW7qAjd5KF/8/23pSoF5vXBE09nxYc8TlmEUM=; b=Wvdx4T0etpdPbxWRf+PxEFJXyobCquw7Ia8NzvSSWzmUeffoQFWCwdClzG+m2Hkk8SGnwz YemrIMC0OdkIuCDMBpWRJZLYEyOEpk0bZYvgjNDOCVi2cH9z7BygdvvfF0ff+TP6/Zp8DF XksTP0UZovQLIQrBYO+RF7TlE+rTDvQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-249-9tsn6XZgPY-p0wHYN_-nmw-1; Thu, 11 Feb 2021 04:49:03 -0500 X-MC-Unique: 9tsn6XZgPY-p0wHYN_-nmw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6F49280364D; Thu, 11 Feb 2021 09:48:58 +0000 (UTC) Received: from [10.36.114.52] (ovpn-114-52.ams2.redhat.com [10.36.114.52]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4AE5010016F4; Thu, 11 Feb 2021 09:48:49 +0000 (UTC) To: Michal Hocko References: <20210208084920.2884-1-rppt@kernel.org> <20210208084920.2884-8-rppt@kernel.org> <20210208212605.GX242749@kernel.org> <20210209090938.GP299309@linux.ibm.com> <20210211071319.GF242749@kernel.org> <0d66baec-1898-987b-7eaf-68a015c027ff@redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Subject: Re: [PATCH v17 07/10] mm: introduce memfd_secret system call to create "secret" memory areas Message-ID: <367808fc-8f5c-10a4-fc0b-a71df616dfce@redhat.com> Date: Thu, 11 Feb 2021 10:48:48 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210211_044911_362913_E7D1B024 X-CRM114-Status: GOOD ( 24.02 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Peter Zijlstra , Catalin Marinas , Dave Hansen , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, "H. Peter Anvin" , Christopher Lameter , Shuah Khan , Thomas Gleixner , Elena Reshetova , linux-arch@vger.kernel.org, Tycho Andersen , linux-nvdimm@lists.01.org, Will Deacon , x86@kernel.org, Matthew Wilcox , Mike Rapoport , Ingo Molnar , Michael Kerrisk , Palmer Dabbelt , Arnd Bergmann , James Bottomley , Hagen Paul Pfeifer , Borislav Petkov , Alexander Viro , Andy Lutomirski , Paul Walmsley , "Kirill A. Shutemov" , Dan Williams , linux-arm-kernel@lists.infradead.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, Palmer Dabbelt , linux-fsdevel@vger.kernel.org, Shakeel Butt , Andrew Morton , Rick Edgecombe , Roman Gushchin , Mike Rapoport Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org >> Some random thoughts regarding files. >> >> What is the page size of secretmem memory? Sometimes we use huge pages, >> sometimes we fallback to 4k pages. So I assume huge pages in general? > > Unless there is an explicit request for hugetlb I would say the page > size is not really important like for any other fds. Huge pages can be > used transparently. If everything is currently allocated/mapped on PTE granularity, then yes I agree. I remember previous versions used to "pool 2MB pages", which might have been problematic (thus, my concerns regarding mmap() etc.). If that part is now gone, good! > >> What are semantics of MADV()/FALLOCATE() etc on such files? > > I would expect the same semantic as regular shmem (memfd_create) except > the memory doesn't have _any_ backing storage which makes it > unevictable. So the reclaim related madv won't work but there shouldn't > be any real reason why e.g. MADV_DONTNEED, WILLNEED, DONT_FORK and > others don't work. Agreed if we don't have hugepage semantics. >> Is userfaultfd() properly fenced? Or does it even work (doubt)? >> >> How does it behave if I mmap(FIXED) something in between? >> In which granularity can I do that (->page-size?)? > > Again, nothing really exceptional here. This is a mapping like any > other from address space manipulation POV. Agreed with the PTE mapping approach. > >> What are other granularity restrictions (->page size)? >> >> Don't want to open a big discussion here, just some random thoughts. >> Maybe it has all been already figured out and most of the answers >> above are "Fails with -EINVAL". > > I think that the behavior should be really in sync with shmem semantic > as much as possible. Most operations should simply work with an > aditional direct map manipulation. There is no real reason to be > special. Some functionality might be missing, e.g. hugetlb support but > that has been traditionally added on top of shmem interface so nothing > really new here. Agreed! -- Thanks, David / dhildenb _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv 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 X-Spam-Level: X-Spam-Status: No, score=-5.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3B5CFC433E0 for ; Thu, 11 Feb 2021 09:50:30 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E8EE364E8A for ; 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Thu, 11 Feb 2021 04:49:03 -0500 X-MC-Unique: 9tsn6XZgPY-p0wHYN_-nmw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6F49280364D; Thu, 11 Feb 2021 09:48:58 +0000 (UTC) Received: from [10.36.114.52] (ovpn-114-52.ams2.redhat.com [10.36.114.52]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4AE5010016F4; Thu, 11 Feb 2021 09:48:49 +0000 (UTC) To: Michal Hocko References: <20210208084920.2884-1-rppt@kernel.org> <20210208084920.2884-8-rppt@kernel.org> <20210208212605.GX242749@kernel.org> <20210209090938.GP299309@linux.ibm.com> <20210211071319.GF242749@kernel.org> <0d66baec-1898-987b-7eaf-68a015c027ff@redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Subject: Re: [PATCH v17 07/10] mm: introduce memfd_secret system call to create "secret" memory areas Message-ID: <367808fc-8f5c-10a4-fc0b-a71df616dfce@redhat.com> Date: Thu, 11 Feb 2021 10:48:48 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210211_044911_446786_2066AF04 X-CRM114-Status: GOOD ( 24.98 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Peter Zijlstra , Catalin Marinas , Dave Hansen , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, "H. Peter Anvin" , Christopher Lameter , Shuah Khan , Thomas Gleixner , Elena Reshetova , linux-arch@vger.kernel.org, Tycho Andersen , linux-nvdimm@lists.01.org, Will Deacon , x86@kernel.org, Matthew Wilcox , Mike Rapoport , Ingo Molnar , Michael Kerrisk , Palmer Dabbelt , Arnd Bergmann , James Bottomley , Hagen Paul Pfeifer , Borislav Petkov , Alexander Viro , Andy Lutomirski , Paul Walmsley , "Kirill A. Shutemov" , Dan Williams , linux-arm-kernel@lists.infradead.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, Palmer Dabbelt , linux-fsdevel@vger.kernel.org, Shakeel Butt , Andrew Morton , Rick Edgecombe , Roman Gushchin , Mike Rapoport Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org >> Some random thoughts regarding files. >> >> What is the page size of secretmem memory? Sometimes we use huge pages, >> sometimes we fallback to 4k pages. So I assume huge pages in general? > > Unless there is an explicit request for hugetlb I would say the page > size is not really important like for any other fds. Huge pages can be > used transparently. If everything is currently allocated/mapped on PTE granularity, then yes I agree. I remember previous versions used to "pool 2MB pages", which might have been problematic (thus, my concerns regarding mmap() etc.). If that part is now gone, good! > >> What are semantics of MADV()/FALLOCATE() etc on such files? > > I would expect the same semantic as regular shmem (memfd_create) except > the memory doesn't have _any_ backing storage which makes it > unevictable. So the reclaim related madv won't work but there shouldn't > be any real reason why e.g. MADV_DONTNEED, WILLNEED, DONT_FORK and > others don't work. Agreed if we don't have hugepage semantics. >> Is userfaultfd() properly fenced? Or does it even work (doubt)? >> >> How does it behave if I mmap(FIXED) something in between? >> In which granularity can I do that (->page-size?)? > > Again, nothing really exceptional here. This is a mapping like any > other from address space manipulation POV. Agreed with the PTE mapping approach. > >> What are other granularity restrictions (->page size)? >> >> Don't want to open a big discussion here, just some random thoughts. >> Maybe it has all been already figured out and most of the answers >> above are "Fails with -EINVAL". > > I think that the behavior should be really in sync with shmem semantic > as much as possible. Most operations should simply work with an > aditional direct map manipulation. There is no real reason to be > special. Some functionality might be missing, e.g. hugetlb support but > that has been traditionally added on top of shmem interface so nothing > really new here. Agreed! -- Thanks, David / dhildenb _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel