From patchwork Mon Nov 7 16:17:21 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 13034723 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 EE3A5C433FE for ; Mon, 7 Nov 2022 16:19:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-Id:Date:Subject:Cc :To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=D1J6YTCgi803JC6qiE06zr3gKIxoc5MyezDVO4QcDEA=; b=Xcz/lTl66/25tB XKZL4i0GRoSzfJYoW2sFSs9b4YT20/8hUwtb0FziYc+nzOJilANG0e9p11+tHohVW823XMKyPpLsI og/bjBzK3vq2nvf85/DByujpDvpl0Nj4ZWMM8gHm00IEoC0nbzYJBRtK4W6poCP440HnX2oaGvk2n bHCjl3HS9yv1hZJvDRaFJs+z/ODLDpRFDn5GQhL0EGkG+0uMTDZe7lVwPiXL37lizkpqzH2e+7Wj0 NKT1hi9HOy3I7HfPkdwsl+ROQNPD6aVrwxft5XFHzd8mLq4U/TGoR6x7Wi5UCftHQNbGXMWX4Xu44 5VfJ1w/j9cay1cU7kHvg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1os4p5-00G6HH-QD; Mon, 07 Nov 2022 16:18:08 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1os4p2-00G6ER-9u for linux-arm-kernel@lists.infradead.org; Mon, 07 Nov 2022 16:18:06 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1667837881; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=9cods/w8rqgeUJG27hSpYwAK3kmd3FHu+oLejBSIpOc=; b=FnI5AqdIS7nrD62ULwHS3lSsoNtcCXrWqjTFyPfQIc2IyWGrpLJk0TYMe/NtmC3knKx5L3 lXiLtMT3thhjTMfKOq8/tOs0ixTtIxhssSlCpe1RcwQsXaUVAZkNH+rtoO64WyecOEdTxO csW4UWnDEn/+6fiyEoSKOHWLbnqD2R0= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-515-izDZkPSsPkGvihn_mMeNNw-1; Mon, 07 Nov 2022 11:17:49 -0500 X-MC-Unique: izDZkPSsPkGvihn_mMeNNw-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id A911185A59D; Mon, 7 Nov 2022 16:17:47 +0000 (UTC) Received: from t480s.redhat.com (unknown [10.39.195.106]) by smtp.corp.redhat.com (Postfix) with ESMTP id E6FEE4B3FC8; Mon, 7 Nov 2022 16:17:41 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, linux-kselftest@vger.kernel.org, David Hildenbrand , Linus Torvalds , Andrew Morton , Jason Gunthorpe , John Hubbard , Peter Xu , Greg Kroah-Hartman , Andrea Arcangeli , Hugh Dickins , Nadav Amit , Vlastimil Babka , Matthew Wilcox , Mike Kravetz , Muchun Song , Lucas Stach , David Airlie , Oded Gabbay , Arnd Bergmann Subject: [PATCH RFC 00/19] mm/gup: remove FOLL_FORCE usage from drivers (reliable R/O long-term pinning) Date: Mon, 7 Nov 2022 17:17:21 +0100 Message-Id: <20221107161740.144456-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221107_081804_445650_BD547EEC X-CRM114-Status: GOOD ( 17.28 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org For now, we did not support reliable R/O long-term pinning in COW mappings. That means, if we would trigger R/O long-term pinning in MAP_PRIVATE mapping, we could end up pinning the (R/O-mapped) shared zeropage or a pagecache page. The next write access would trigger a write fault and replace the pinned page by an exclusive anonymous page in the process page table; whatever the process would write to that private page copy would not be visible by the owner of the previous page pin: for example, RDMA could read stale data. The end result is essentially an unexpected and hard-to-debug memory corruption. Some drivers tried working around that limitation by using "FOLL_FORCE|FOLL_WRITE|FOLL_LONGTERM" for R/O long-term pinning for now. FOLL_WRITE would trigger a write fault, if required, and break COW before pinning the page. FOLL_FORCE is required because the VMA might lack write permissions, and drivers wanted to make that working as well, just like one would expect (no write access, but still triggering a write access to break COW). However, that is not a practical solution, because (1) Drivers that don't stick to that undocumented and debatable pattern would still run into that issue. For example, VFIO only uses FOLL_LONGTERM for R/O long-term pinning. (2) Using FOLL_WRITE just to work around a COW mapping + page pinning limitation is unintuitive. FOLL_WRITE would, for example, mark the page softdirty or trigger uffd-wp, even though, there actually isn't going to be any write access. (3) The purpose of FOLL_FORCE is debug access, not access without lack of VMA permissions by arbitrarty drivers. So instead, make R/O long-term pinning work as expected, by breaking COW in a COW mapping early, such that we can remove any FOLL_FORCE usage from drivers. More details in patch #8. Patches #1--#3 add COW tests for non-anonymous pages. Patches #4--#7 prepare core MM for extended FAULT_FLAG_UNSHARE support in COW mappings. Patch #8 implements reliable R/O long-term pinning in COW mappings Patches #9--#19 remove any FOLL_FORCE usage from drivers. I'm refraining from CCing all driver maintainers on the whole patch set. Cc: Linus Torvalds Cc: Andrew Morton Cc: Jason Gunthorpe Cc: John Hubbard Cc: Peter Xu Cc: Greg Kroah-Hartman Cc: Andrea Arcangeli Cc: Hugh Dickins Cc: Nadav Amit Cc: Vlastimil Babka Cc: Matthew Wilcox (Oracle) Cc: Mike Kravetz Cc: Muchun Song Cc: Shuah Khan Cc: David Airlie Cc: Oded Gabbay Cc: Arnd Bergmann David Hildenbrand (19): selftests/vm: anon_cow: prepare for non-anonymous COW tests selftests/vm: cow: basic COW tests for non-anonymous pages selftests/vm: cow: R/O long-term pinning reliability tests for non-anon pages mm: add early FAULT_FLAG_UNSHARE consistency checks mm: add early FAULT_FLAG_WRITE consistency checks mm: rework handling in do_wp_page() based on private vs. shared mappings mm: don't call vm_ops->huge_fault() in wp_huge_pmd()/wp_huge_pud() for private mappings mm: extend FAULT_FLAG_UNSHARE support to anything in a COW mapping mm/gup: reliable R/O long-term pinning in COW mappings RDMA/umem: remove FOLL_FORCE usage RDMA/usnic: remove FOLL_FORCE usage RDMA/siw: remove FOLL_FORCE usage media: videobuf-dma-sg: remove FOLL_FORCE usage drm/etnaviv: remove FOLL_FORCE usage media: pci/ivtv: remove FOLL_FORCE usage mm/frame-vector: remove FOLL_FORCE usage drm/exynos: remove FOLL_FORCE usage RDMA/hw/qib/qib_user_pages: remove FOLL_FORCE usage habanalabs: remove FOLL_FORCE usage drivers/gpu/drm/etnaviv/etnaviv_gem.c | 8 +- drivers/gpu/drm/exynos/exynos_drm_g2d.c | 2 +- drivers/infiniband/core/umem.c | 8 +- drivers/infiniband/hw/qib/qib_user_pages.c | 2 +- drivers/infiniband/hw/usnic/usnic_uiom.c | 9 +- drivers/infiniband/sw/siw/siw_mem.c | 9 +- drivers/media/common/videobuf2/frame_vector.c | 2 +- drivers/media/pci/ivtv/ivtv-udma.c | 2 +- drivers/media/pci/ivtv/ivtv-yuv.c | 5 +- drivers/media/v4l2-core/videobuf-dma-sg.c | 14 +- drivers/misc/habanalabs/common/memory.c | 3 +- include/linux/mm.h | 27 +- include/linux/mm_types.h | 8 +- mm/gup.c | 10 +- mm/huge_memory.c | 5 +- mm/hugetlb.c | 12 +- mm/memory.c | 97 +++-- tools/testing/selftests/vm/.gitignore | 2 +- tools/testing/selftests/vm/Makefile | 10 +- tools/testing/selftests/vm/check_config.sh | 4 +- .../selftests/vm/{anon_cow.c => cow.c} | 387 +++++++++++++++++- tools/testing/selftests/vm/run_vmtests.sh | 8 +- 22 files changed, 516 insertions(+), 118 deletions(-) rename tools/testing/selftests/vm/{anon_cow.c => cow.c} (74%)