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 3643CC433FE for ; Mon, 7 Mar 2022 14:34:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243248AbiCGOfA (ORCPT ); Mon, 7 Mar 2022 09:35:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33378 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243243AbiCGOe7 (ORCPT ); Mon, 7 Mar 2022 09:34:59 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 49E9B5F4D4 for ; Mon, 7 Mar 2022 06:34:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1646663644; 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=EFYNbblCnNcuaPx8LOQ1Hn2woAp9Zpf6py8Ud+OJaTY=; b=JHkA6iHsw6poTI57aQopSoC4FjWrUtIrxyKlpOU3vBRG2DSVZYvMdC75dBgEHV46h6FDVE 8C4zsRyQlB1N/AX2pVS2FEsPDkrGiciZYIME3zy7/QREXjjzNWFm2n5uPZe9H7Q8ZC4VCD Aib3JK1eNIUIti8k2BTbGvt54rtaMJg= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-436-1VV6B2v6OsWGtroq-nkPzw-1; Mon, 07 Mar 2022 09:34:03 -0500 X-MC-Unique: 1VV6B2v6OsWGtroq-nkPzw-1 Received: by mail-wm1-f71.google.com with SMTP id 187-20020a1c19c4000000b0037cc0d56524so7947027wmz.2 for ; Mon, 07 Mar 2022 06:34:03 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent :content-language:to:cc:references:from:organization:subject :in-reply-to:content-transfer-encoding; bh=EFYNbblCnNcuaPx8LOQ1Hn2woAp9Zpf6py8Ud+OJaTY=; b=2y4lvYU5K9DNorENjLco7ClfA8YY0aSaCOFtmERbj7yf0JwITi5RKSa6kAcs1AalQO ORvpbKddbMJIxsGTjK4EkfZ9DYV+z5+RUjMSkGyjpLY955oNzNXHcIMn1wkBtuowPBfY h6nl6fCw+Nr5UPLH5fb4TZv3GcLveZgkwLJWN1bwrKFb0hygve/GSiOMusLsVeh8R1/8 c9lWbtqMeAFjNf1ffvns00zldVOI9CoCiqIwNYlMvPny/yO/5MHG20PonW4k9UZVWmON iLoDCi+lSaVKxtBZPuimyCrJIOXkFmWzSOkab/3/sYlmkdZ7wz0oRvVV+faOP6mHWK17 mePg== X-Gm-Message-State: AOAM533vtZeMiPZhaQ3/eBrfa8IqRoQX/P4E7DwzuJiufRKJ0gYQY750 u/ObHItMwSwackFvehPVynYv/PA4MYHAwidGPZvyd2nktsOW/kOUUlM8hip9lduB59e1MPw9VQX NTGv1v601NJQDqyCSI6j5KtD5LQ== X-Received: by 2002:a7b:ca49:0:b0:389:bcde:f7ab with SMTP id m9-20020a7bca49000000b00389bcdef7abmr1185205wml.7.1646663642075; Mon, 07 Mar 2022 06:34:02 -0800 (PST) X-Google-Smtp-Source: ABdhPJxPQNqWxZSPrdYEmAfxwtZ3y4N0Kf0xHJe42MVbdVGbGB8hJ9qV6tBxdbfd3Fa3fXlIgu+yCQ== X-Received: by 2002:a7b:ca49:0:b0:389:bcde:f7ab with SMTP id m9-20020a7bca49000000b00389bcdef7abmr1185173wml.7.1646663641772; Mon, 07 Mar 2022 06:34:01 -0800 (PST) Received: from ?IPV6:2003:cb:c705:1e00:8d67:f75a:a8ae:dc02? (p200300cbc7051e008d67f75aa8aedc02.dip0.t-ipconnect.de. [2003:cb:c705:1e00:8d67:f75a:a8ae:dc02]) by smtp.gmail.com with ESMTPSA id h12-20020a5d548c000000b001f1f99e7792sm2398939wrv.111.2022.03.07.06.33.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 07 Mar 2022 06:33:54 -0800 (PST) Message-ID: Date: Mon, 7 Mar 2022 15:33:52 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Content-Language: en-US To: Jarkko Sakkinen Cc: linux-mm@kvack.org, Dave Hansen , Nathaniel McCallum , Reinette Chatre , Andrew Morton , linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org, Florian Fainelli , Thomas Bogendoerfer , Matthew Auld , =?UTF-8?Q?Thomas_Hellstr=c3=b6m?= , Daniel Vetter , Jason Ekstrand , Chris Wilson , Maarten Lankhorst , Greg Kroah-Hartman , Tvrtko Ursulin , Vasily Averin , Shakeel Butt , Michal Hocko , zhangyiru , Alexey Gladkov , Alexander Mikhalitsyn , linux-mips@vger.kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, codalist@coda.cs.cmu.edu, linux-unionfs@vger.kernel.org, linux-fsdevel@vger.kernel.org References: <20220306053211.135762-1-jarkko@kernel.org> From: David Hildenbrand Organization: Red Hat Subject: Re: [PATCH RFC 0/3] MAP_POPULATE for device memory In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-unionfs@vger.kernel.org On 07.03.22 15:22, Jarkko Sakkinen wrote: > On Mon, Mar 07, 2022 at 11:12:44AM +0100, David Hildenbrand wrote: >> On 06.03.22 06:32, Jarkko Sakkinen wrote: >>> For device memory (aka VM_IO | VM_PFNMAP) MAP_POPULATE does nothing. Allow >>> to use that for initializing the device memory by providing a new callback >>> f_ops->populate() for the purpose. >>> >>> SGX patches are provided to show the callback in context. >>> >>> An obvious alternative is a ioctl but it is less elegant and requires >>> two syscalls (mmap + ioctl) per memory range, instead of just one >>> (mmap). >> >> What about extending MADV_POPULATE_READ | MADV_POPULATE_WRITE to support >> VM_IO | VM_PFNMAP (as well?) ? > > What would be a proper point to bind that behaviour? For mmap/mprotect it'd > be probably populate_vma_page_range() because that would span both mmap() > and mprotect() (Dave's suggestion in this thread). MADV_POPULATE_* ends up in faultin_vma_page_range(), right next to populate_vma_page_range(). So it might require a similar way to hook into the driver I guess. > > For MAP_POPULATE I did not have hard proof to show that it would be used > by other drivers but for madvice() you can find at least a few ioctl > based implementations: > > $ git grep -e madv --and \( -e ioc \) drivers/ > drivers/gpu/drm/i915/gem/i915_gem_ioctls.h:int i915_gem_madvise_ioctl(struct drm_device *dev, void *data, > drivers/gpu/drm/i915/i915_driver.c: DRM_IOCTL_DEF_DRV(I915_GEM_MADVISE, i915_gem_madvise_ioctl, DRM_RENDER_ALLOW), > drivers/gpu/drm/i915/i915_gem.c:i915_gem_madvise_ioctl(struct drm_device *dev, void *data, > drivers/gpu/drm/msm/msm_drv.c:static int msm_ioctl_gem_madvise(struct drm_device *dev, void *data, > drivers/gpu/drm/msm/msm_drv.c: DRM_IOCTL_DEF_DRV(MSM_GEM_MADVISE, msm_ioctl_gem_madvise, DRM_RENDER_ALLOW), > drivers/gpu/drm/panfrost/panfrost_drv.c:static int panfrost_ioctl_madvise(struct drm_device *dev, void *data, > drivers/gpu/drm/vc4/vc4_drv.c: DRM_IOCTL_DEF_DRV(VC4_GEM_MADVISE, vc4_gem_madvise_ioctl, DRM_RENDER_ALLOW), > drivers/gpu/drm/vc4/vc4_drv.h:int vc4_gem_madvise_ioctl(struct drm_device *dev, void *data, > drivers/gpu/drm/vc4/vc4_gem.c:int vc4_gem_madvise_ioctl(struct drm_device *dev, void *data, > > IMHO this also provides supportive claim for MAP_POPULATE, and yeah, I > agree that to be consistent implementation, both madvice() and MAP_POPULATE > should work. MADV_POPULATE_WRITE + MADV_DONTNEED/FALLOC_FL_PUNCH_HOLE is one way to dynamically manage memory consumption inside a sparse memory mapping (preallocate/populate via MADV_POPULATE_WRITE, discard via MADV_DONTNEED/FALLOC_FL_PUNCH_HOLE). Extending that whole mechanism to deal with VM_IO | VM_PFNMAP mappings as well could be interesting. At least I herd about some ideas where we might want to dynamically expose memory to a VM (via virtio-mem) inside a sparse memory mapping, and the memory in that sparse memory mapping is provided from a dedicated memory pool managed by a device driver -- not just using ordinary anonymous/file/hugetlb memory as we do right now. Now, this is certainly stuff for the future, I just wanted to mention it. -- Thanks, David / dhildenb