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=-11.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 5B5D3C433DB for ; Tue, 12 Jan 2021 12:52:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 059A522CBE for ; Tue, 12 Jan 2021 12:52:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388635AbhALMwb (ORCPT ); Tue, 12 Jan 2021 07:52:31 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:56579 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727998AbhALMwb (ORCPT ); Tue, 12 Jan 2021 07:52:31 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1610455864; 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=3di3WiIDCT0haTp37A4dlkvRPB/If8ZucUraJvNLxLM=; b=T5zBIKSq8jeWg2IfnOkl8PIuY7IhH25GSnw5nO6JkAWlOy5PenBohwvbz0/oJ/J0dpPa8x 5L3yEp4cjHm+P9ZkeHQ9GRrtZCJQa8rbiDdIaO2tYEXJNu026qL8mi3Rq60QKMRA1zflNN 6b+nc6cRb37g9B7e0iRUjbpbrKkvx/I= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-18-gX1JbrTHNbiy-eXXv6JE5Q-1; Tue, 12 Jan 2021 07:48:34 -0500 X-MC-Unique: gX1JbrTHNbiy-eXXv6JE5Q-1 Received: by mail-wr1-f70.google.com with SMTP id z8so1117331wrh.5 for ; Tue, 12 Jan 2021 04:48:34 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=3di3WiIDCT0haTp37A4dlkvRPB/If8ZucUraJvNLxLM=; b=CzZiLoODAJC8BOWVVBMX0fR99Rs67kDPtY+T2NSR790fZ4PewF0NOVb0gNAMUho8HA iffdldLPuRvfSV8IKNawj2AbeMgnXkJ4kW2tqjLZ2K3/4+RUmVBqG4j8xK46u41WuxrM PuW3GG/TnweUXZSbvJo1Qkn6lACHiM5bDTlbgwBhDBiPAP98BlA1QfOvTXMtk6ofDHFr sxsAguPw75CJeH+UeYUnmsArSLOILLNCsVOd9OF60dckIEUWTcW9MPLPg3LxXMKxMpVU P3uCsAwdy2KHrHNbrEhMdubAWkp1DvsWPWP4pu+2+YzFRBgwIvnQTRtAP6emIfhMBjvv WslA== X-Gm-Message-State: AOAM532XGPzoPyG2vYITaW/0JHIsZUcAAD1zbTodXrZjFHwRvsRcsWBH +6akkwRZAFcUoeyywkYD9YIFNheay0pzI3rXw+QkrLzNizWTW/TWPRMcm0FqivyW5KzWlVUFkSY kD91/SdQa1dlDpx6QXJ1fRmqa X-Received: by 2002:a5d:6204:: with SMTP id y4mr4195221wru.48.1610455713439; Tue, 12 Jan 2021 04:48:33 -0800 (PST) X-Google-Smtp-Source: ABdhPJzjLRoOBZSP/z6909MxSjSSPfO+4mnMDOjffdHUYYKda5rFiHxPiZst9Fk7g0GNmnbF8Daesw== X-Received: by 2002:a5d:6204:: with SMTP id y4mr4195206wru.48.1610455713246; Tue, 12 Jan 2021 04:48:33 -0800 (PST) Received: from redhat.com (bzq-79-178-32-166.red.bezeqint.net. [79.178.32.166]) by smtp.gmail.com with ESMTPSA id b10sm4019102wmj.5.2021.01.12.04.48.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 Jan 2021 04:48:32 -0800 (PST) Date: Tue, 12 Jan 2021 07:48:27 -0500 From: "Michael S. Tsirkin" To: Adrian Catangiu Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, kvm@vger.kernel.org, linux-s390@vger.kernel.org, gregkh@linuxfoundation.org, graf@amazon.com, arnd@arndb.de, ebiederm@xmission.com, rppt@kernel.org, 0x7f454c46@gmail.com, borntraeger@de.ibm.com, Jason@zx2c4.com, jannh@google.com, w@1wt.eu, colmmacc@amazon.com, luto@kernel.org, tytso@mit.edu, ebiggers@kernel.org, dwmw@amazon.co.uk, bonzini@gnu.org, sblbir@amazon.com, raduweis@amazon.com, corbet@lwn.net, mhocko@kernel.org, rafael@kernel.org, pavel@ucw.cz, mpe@ellerman.id.au, areber@redhat.com, ovzxemul@gmail.com, avagin@gmail.com, ptikhomirov@virtuozzo.com, gil@azul.com, asmehra@redhat.com, dgunigun@redhat.com, vijaysun@ca.ibm.com, oridgar@gmail.com, ghammer@redhat.com Subject: Re: [PATCH v4 0/2] System Generation ID driver and VMGENID backend Message-ID: <20210112074658-mutt-send-email-mst@kernel.org> References: <1610453760-13812-1-git-send-email-acatan@amazon.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1610453760-13812-1-git-send-email-acatan@amazon.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 12, 2021 at 02:15:58PM +0200, Adrian Catangiu wrote: > This feature is aimed at virtualized or containerized environments > where VM or container snapshotting duplicates memory state, which is a > challenge for applications that want to generate unique data such as > request IDs, UUIDs, and cryptographic nonces. > > The patch set introduces a mechanism that provides a userspace > interface for applications and libraries to be made aware of uniqueness > breaking events such as VM or container snapshotting, and allow them to > react and adapt to such events. > > Solving the uniqueness problem strongly enough for cryptographic > purposes requires a mechanism which can deterministically reseed > userspace PRNGs with new entropy at restore time. This mechanism must > also support the high-throughput and low-latency use-cases that led > programmers to pick a userspace PRNG in the first place; be usable by > both application code and libraries; allow transparent retrofitting > behind existing popular PRNG interfaces without changing application > code; it must be efficient, especially on snapshot restore; and be > simple enough for wide adoption. > > The first patch in the set implements a device driver which exposes a > read-only device /dev/sysgenid to userspace, which contains a > monotonically increasing u32 generation counter. Libraries and > applications are expected to open() the device, and then call read() > which blocks until the SysGenId changes. Following an update, read() > calls no longer block until the application acknowledges the new > SysGenId by write()ing it back to the device. Non-blocking read() calls > return EAGAIN when there is no new SysGenId available. Alternatively, > libraries can mmap() the device to get a single shared page which > contains the latest SysGenId at offset 0. Looking at some specifications, the gen ID might actually be located at an arbitrary address. How about instead of hard-coding the offset, we expose it e.g. in sysfs? > SysGenId also supports a notification mechanism exposed as two IOCTLs > on the device. SYSGENID_GET_OUTDATED_WATCHERS immediately returns the > number of file descriptors to the device that were open during the last > SysGenId change but have not yet acknowledged the new id. > SYSGENID_WAIT_WATCHERS blocks until there are no open file handles on > the device which haven’t acknowledged the new id. These two interfaces > are intended for serverless and container control planes, which want to > confirm that all application code has detected and reacted to the new > SysGenId before sending an invoke to the newly-restored sandbox. > > The second patch in the set adds a VmGenId driver which makes use of > the ACPI vmgenid device to drive SysGenId and to reseed kernel entropy > on VM snapshots. > > --- > > v3 -> v4: > > - split functionality in two separate kernel modules: > 1. drivers/misc/sysgenid.c which provides the generic userspace > interface and mechanisms > 2. drivers/virt/vmgenid.c as VMGENID acpi device driver that seeds > kernel entropy and acts as a driving backend for the generic > sysgenid > - renamed /dev/vmgenid -> /dev/sysgenid > - renamed uapi header file vmgenid.h -> sysgenid.h > - renamed ioctls VMGENID_* -> SYSGENID_* > - added ‘min_gen’ parameter to SYSGENID_FORCE_GEN_UPDATE ioctl > - fixed races in documentation examples > - various style nits > - rebased on top of linus latest > > v2 -> v3: > > - separate the core driver logic and interface, from the ACPI device. > The ACPI vmgenid device is now one possible backend. > - fix issue when timeout=0 in VMGENID_WAIT_WATCHERS > - add locking to avoid races between fs ops handlers and hw irq > driven generation updates > - change VMGENID_WAIT_WATCHERS ioctl so if the current caller is > outdated or a generation change happens while waiting (thus making > current caller outdated), the ioctl returns -EINTR to signal the > user to handle event and retry. Fixes blocking on oneself. > - add VMGENID_FORCE_GEN_UPDATE ioctl conditioned by > CAP_CHECKPOINT_RESTORE capability, through which software can force > generation bump. > > v1 -> v2: > > - expose to userspace a monotonically increasing u32 Vm Gen Counter > instead of the hw VmGen UUID > - since the hw/hypervisor-provided 128-bit UUID is not public > anymore, add it to the kernel RNG as device randomness > - insert driver page containing Vm Gen Counter in the user vma in > the driver's mmap handler instead of using a fault handler > - turn driver into a misc device driver to auto-create /dev/vmgenid > - change ioctl arg to avoid leaking kernel structs to userspace > - update documentation > - various nits > - rebase on top of linus latest > > Adrian Catangiu (2): > drivers/misc: sysgenid: add system generation id driver > drivers/virt: vmgenid: add vm generation id driver > > Documentation/misc-devices/sysgenid.rst | 240 +++++++++++++++++++++++++ > Documentation/virt/vmgenid.rst | 34 ++++ > drivers/misc/Kconfig | 16 ++ > drivers/misc/Makefile | 1 + > drivers/misc/sysgenid.c | 298 ++++++++++++++++++++++++++++++++ > drivers/virt/Kconfig | 14 ++ > drivers/virt/Makefile | 1 + > drivers/virt/vmgenid.c | 153 ++++++++++++++++ > include/uapi/linux/sysgenid.h | 18 ++ > 9 files changed, 775 insertions(+) > create mode 100644 Documentation/misc-devices/sysgenid.rst > create mode 100644 Documentation/virt/vmgenid.rst > create mode 100644 drivers/misc/sysgenid.c > create mode 100644 drivers/virt/vmgenid.c > create mode 100644 include/uapi/linux/sysgenid.h > > -- > 2.7.4 > > > > > Amazon Development Center (Romania) S.R.L. registered office: 27A Sf. Lazar Street, UBC5, floor 2, Iasi, Iasi County, 700045, Romania. Registered in Romania. Registration number J22/2621/2005. 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[79.178.32.166]) by smtp.gmail.com with ESMTPSA id b10sm4019102wmj.5.2021.01.12.04.48.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 Jan 2021 04:48:32 -0800 (PST) Date: Tue, 12 Jan 2021 07:48:27 -0500 From: "Michael S. Tsirkin" To: Adrian Catangiu Subject: Re: [PATCH v4 0/2] System Generation ID driver and VMGENID backend Message-ID: <20210112074658-mutt-send-email-mst@kernel.org> References: <1610453760-13812-1-git-send-email-acatan@amazon.com> MIME-Version: 1.0 In-Reply-To: <1610453760-13812-1-git-send-email-acatan@amazon.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.251, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jason@zx2c4.com, dgunigun@redhat.com, kvm@vger.kernel.org, linux-doc@vger.kernel.org, ghammer@redhat.com, vijaysun@ca.ibm.com, 0x7f454c46@gmail.com, qemu-devel@nongnu.org, mhocko@kernel.org, oridgar@gmail.com, avagin@gmail.com, pavel@ucw.cz, ptikhomirov@virtuozzo.com, linux-s390@vger.kernel.org, corbet@lwn.net, mpe@ellerman.id.au, rafael@kernel.org, ebiggers@kernel.org, borntraeger@de.ibm.com, sblbir@amazon.com, bonzini@gnu.org, arnd@arndb.de, jannh@google.com, raduweis@amazon.com, asmehra@redhat.com, graf@amazon.com, rppt@kernel.org, luto@kernel.org, gil@azul.com, colmmacc@amazon.com, tytso@mit.edu, gregkh@linuxfoundation.org, areber@redhat.com, linux-kernel@vger.kernel.org, ebiederm@xmission.com, ovzxemul@gmail.com, w@1wt.eu, dwmw@amazon.co.uk Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Jan 12, 2021 at 02:15:58PM +0200, Adrian Catangiu wrote: > This feature is aimed at virtualized or containerized environments > where VM or container snapshotting duplicates memory state, which is a > challenge for applications that want to generate unique data such as > request IDs, UUIDs, and cryptographic nonces. > > The patch set introduces a mechanism that provides a userspace > interface for applications and libraries to be made aware of uniqueness > breaking events such as VM or container snapshotting, and allow them to > react and adapt to such events. > > Solving the uniqueness problem strongly enough for cryptographic > purposes requires a mechanism which can deterministically reseed > userspace PRNGs with new entropy at restore time. This mechanism must > also support the high-throughput and low-latency use-cases that led > programmers to pick a userspace PRNG in the first place; be usable by > both application code and libraries; allow transparent retrofitting > behind existing popular PRNG interfaces without changing application > code; it must be efficient, especially on snapshot restore; and be > simple enough for wide adoption. > > The first patch in the set implements a device driver which exposes a > read-only device /dev/sysgenid to userspace, which contains a > monotonically increasing u32 generation counter. Libraries and > applications are expected to open() the device, and then call read() > which blocks until the SysGenId changes. Following an update, read() > calls no longer block until the application acknowledges the new > SysGenId by write()ing it back to the device. Non-blocking read() calls > return EAGAIN when there is no new SysGenId available. Alternatively, > libraries can mmap() the device to get a single shared page which > contains the latest SysGenId at offset 0. Looking at some specifications, the gen ID might actually be located at an arbitrary address. How about instead of hard-coding the offset, we expose it e.g. in sysfs? > SysGenId also supports a notification mechanism exposed as two IOCTLs > on the device. SYSGENID_GET_OUTDATED_WATCHERS immediately returns the > number of file descriptors to the device that were open during the last > SysGenId change but have not yet acknowledged the new id. > SYSGENID_WAIT_WATCHERS blocks until there are no open file handles on > the device which haven’t acknowledged the new id. These two interfaces > are intended for serverless and container control planes, which want to > confirm that all application code has detected and reacted to the new > SysGenId before sending an invoke to the newly-restored sandbox. > > The second patch in the set adds a VmGenId driver which makes use of > the ACPI vmgenid device to drive SysGenId and to reseed kernel entropy > on VM snapshots. > > --- > > v3 -> v4: > > - split functionality in two separate kernel modules: > 1. drivers/misc/sysgenid.c which provides the generic userspace > interface and mechanisms > 2. drivers/virt/vmgenid.c as VMGENID acpi device driver that seeds > kernel entropy and acts as a driving backend for the generic > sysgenid > - renamed /dev/vmgenid -> /dev/sysgenid > - renamed uapi header file vmgenid.h -> sysgenid.h > - renamed ioctls VMGENID_* -> SYSGENID_* > - added ‘min_gen’ parameter to SYSGENID_FORCE_GEN_UPDATE ioctl > - fixed races in documentation examples > - various style nits > - rebased on top of linus latest > > v2 -> v3: > > - separate the core driver logic and interface, from the ACPI device. > The ACPI vmgenid device is now one possible backend. > - fix issue when timeout=0 in VMGENID_WAIT_WATCHERS > - add locking to avoid races between fs ops handlers and hw irq > driven generation updates > - change VMGENID_WAIT_WATCHERS ioctl so if the current caller is > outdated or a generation change happens while waiting (thus making > current caller outdated), the ioctl returns -EINTR to signal the > user to handle event and retry. Fixes blocking on oneself. > - add VMGENID_FORCE_GEN_UPDATE ioctl conditioned by > CAP_CHECKPOINT_RESTORE capability, through which software can force > generation bump. > > v1 -> v2: > > - expose to userspace a monotonically increasing u32 Vm Gen Counter > instead of the hw VmGen UUID > - since the hw/hypervisor-provided 128-bit UUID is not public > anymore, add it to the kernel RNG as device randomness > - insert driver page containing Vm Gen Counter in the user vma in > the driver's mmap handler instead of using a fault handler > - turn driver into a misc device driver to auto-create /dev/vmgenid > - change ioctl arg to avoid leaking kernel structs to userspace > - update documentation > - various nits > - rebase on top of linus latest > > Adrian Catangiu (2): > drivers/misc: sysgenid: add system generation id driver > drivers/virt: vmgenid: add vm generation id driver > > Documentation/misc-devices/sysgenid.rst | 240 +++++++++++++++++++++++++ > Documentation/virt/vmgenid.rst | 34 ++++ > drivers/misc/Kconfig | 16 ++ > drivers/misc/Makefile | 1 + > drivers/misc/sysgenid.c | 298 ++++++++++++++++++++++++++++++++ > drivers/virt/Kconfig | 14 ++ > drivers/virt/Makefile | 1 + > drivers/virt/vmgenid.c | 153 ++++++++++++++++ > include/uapi/linux/sysgenid.h | 18 ++ > 9 files changed, 775 insertions(+) > create mode 100644 Documentation/misc-devices/sysgenid.rst > create mode 100644 Documentation/virt/vmgenid.rst > create mode 100644 drivers/misc/sysgenid.c > create mode 100644 drivers/virt/vmgenid.c > create mode 100644 include/uapi/linux/sysgenid.h > > -- > 2.7.4 > > > > > Amazon Development Center (Romania) S.R.L. registered office: 27A Sf. Lazar Street, UBC5, floor 2, Iasi, Iasi County, 700045, Romania. Registered in Romania. Registration number J22/2621/2005.