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=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 9BA03C352A4 for ; Wed, 12 Feb 2020 20:56:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5766D2467B for ; Wed, 12 Feb 2020 20:56:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="qXED9FBc" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727692AbgBLU4d (ORCPT ); Wed, 12 Feb 2020 15:56:33 -0500 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:15729 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727138AbgBLU4d (ORCPT ); Wed, 12 Feb 2020 15:56:33 -0500 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Wed, 12 Feb 2020 12:55:25 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Wed, 12 Feb 2020 12:56:30 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Wed, 12 Feb 2020 12:56:30 -0800 Received: from [10.40.101.172] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Wed, 12 Feb 2020 20:56:22 +0000 Subject: Re: [PATCH v12 Kernel 1/7] vfio: KABI for migration interface for device state To: Alex Williamson CC: , , , , , , , , , , , , , , , , , , , , References: <1581104554-10704-1-git-send-email-kwankhede@nvidia.com> <1581104554-10704-2-git-send-email-kwankhede@nvidia.com> <20200210102515.0c85cc0a@x1.home> X-Nvconfidentiality: public From: Kirti Wankhede Message-ID: <3f1ef595-ba6d-bcf5-2888-f81e5fdf67ab@nvidia.com> Date: Thu, 13 Feb 2020 02:26:18 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <20200210102515.0c85cc0a@x1.home> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1581540926; bh=/R2EAWhBdczIhC7RjLy9FbGGR0s5RMQq1NYUMV+QgEQ=; h=X-PGP-Universal:Subject:To:CC:References:X-Nvconfidentiality:From: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=qXED9FBcU0G7CLndDOhZH0WWQP3xAfgdygLX76QwxsjIyxe1BPdjC8+oy/VNVJP4s 5QmQO9UVLgmCF3R8ORQSVoIRPHFZfYOr9AgdG/f0C+LHAP5p/OZwfmZazzanBvybRL vQncwOEkOXT7wgl9MHgpT6EeVc/NCsAzTSrKxdeTBdYVePO0jPiqqjumIzXGLt3EOL 306sixFBhUEDe6q2nfhi/uXRAIIpy146n4MI9H321SdkQa3TBKddT/poSFNnRbgjpR 9v1pq7fKwC1B8jNFdbDSzjMh7NY/qbxN9M9w6e6vZyKl0xbd0w/SdQEBnFShr2tQfU vbpsjbxSFtfXg== Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 2/10/2020 10:55 PM, Alex Williamson wrote: > On Sat, 8 Feb 2020 01:12:28 +0530 > Kirti Wankhede wrote: > >> - Defined MIGRATION region type and sub-type. >> >> - Defined vfio_device_migration_info structure which will be placed at 0th >> offset of migration region to get/set VFIO device related information. >> Defined members of structure and usage on read/write access. >> >> - Defined device states and state transition details. >> >> - Defined sequence to be followed while saving and resuming VFIO device. >> >> Signed-off-by: Kirti Wankhede >> Reviewed-by: Neo Jia >> --- >> include/uapi/linux/vfio.h | 208 ++++++++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 208 insertions(+) >> >> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h >> index 9e843a147ead..572242620ce9 100644 >> --- a/include/uapi/linux/vfio.h >> +++ b/include/uapi/linux/vfio.h >> @@ -305,6 +305,7 @@ struct vfio_region_info_cap_type { >> #define VFIO_REGION_TYPE_PCI_VENDOR_MASK (0xffff) >> #define VFIO_REGION_TYPE_GFX (1) >> #define VFIO_REGION_TYPE_CCW (2) >> +#define VFIO_REGION_TYPE_MIGRATION (3) >> >> /* sub-types for VFIO_REGION_TYPE_PCI_* */ >> >> @@ -379,6 +380,213 @@ struct vfio_region_gfx_edid { >> /* sub-types for VFIO_REGION_TYPE_CCW */ >> #define VFIO_REGION_SUBTYPE_CCW_ASYNC_CMD (1) >> >> +/* sub-types for VFIO_REGION_TYPE_MIGRATION */ >> +#define VFIO_REGION_SUBTYPE_MIGRATION (1) >> + >> +/* >> + * Structure vfio_device_migration_info is placed at 0th offset of >> + * VFIO_REGION_SUBTYPE_MIGRATION region to get/set VFIO device related migration >> + * information. Field accesses from this structure are only supported at their >> + * native width and alignment, otherwise the result is undefined and vendor >> + * drivers should return an error. >> + * >> + * device_state: (read/write) >> + * - User application writes this field to inform vendor driver about the >> + * device state to be transitioned to. >> + * - Vendor driver should take necessary actions to change device state. >> + * On successful transition to given state, vendor driver should return >> + * success on write(device_state, state) system call. If device state >> + * transition fails, vendor driver should return error, -EFAULT. > > s/error, -EFAULT/an appropriate -errno for the fault condition/ > >> + * - On user application side, if device state transition fails, i.e. if >> + * write(device_state, state) returns error, read device_state again to >> + * determine the current state of the device from vendor driver. >> + * - Vendor driver should return previous state of the device unless vendor >> + * driver has encountered an internal error, in which case vendor driver >> + * may report the device_state VFIO_DEVICE_STATE_ERROR. >> + * - User application must use the device reset ioctl in order to recover >> + * the device from VFIO_DEVICE_STATE_ERROR state. If the device is >> + * indicated in a valid device state via reading device_state, the user >> + * application may decide attempt to transition the device to any valid >> + * state reachable from the current state or terminate itself. >> + * >> + * device_state consists of 3 bits: >> + * - If bit 0 set, indicates _RUNNING state. When it's clear, that >> + * indicates _STOP state. When device is changed to _STOP, driver should >> + * stop device before write() returns. >> + * - If bit 1 set, indicates _SAVING state. When set, that indicates driver >> + * should start gathering device state information which will be provided >> + * to VFIO user application to save device's state. >> + * - If bit 2 set, indicates _RESUMING state. When set, that indicates >> + * prepare to resume device, data provided through migration region >> + * should be used to resume device. >> + * Bits 3 - 31 are reserved for future use. In order to preserve them, >> + * user application should perform read-modify-write operation on this >> + * field when modifying the specified bits. >> + * >> + * +------- _RESUMING >> + * |+------ _SAVING >> + * ||+----- _RUNNING >> + * ||| >> + * 000b => Device Stopped, not saving or resuming >> + * 001b => Device running state, default state >> + * 010b => Stop Device & save device state, stop-and-copy state >> + * 011b => Device running and save device state, pre-copy state >> + * 100b => Device stopped and device state is resuming >> + * 101b => Invalid state >> + * 110b => Error state >> + * 111b => Invalid state >> + * >> + * State transitions: >> + * >> + * _RESUMING _RUNNING Pre-copy Stop-and-copy _STOP >> + * (100b) (001b) (011b) (010b) (000b) >> + * 0. Running or Default state >> + * | >> + * >> + * 1. Normal Shutdown (optional) >> + * |------------------------------------->| >> + * >> + * 2. Save state or Suspend >> + * |------------------------->|---------->| >> + * >> + * 3. Save state during live migration >> + * |----------->|------------>|---------->| >> + * >> + * 4. Resuming >> + * |<---------| >> + * >> + * 5. Resumed >> + * |--------->| >> + * >> + * 0. Default state of VFIO device is _RUNNNG when user application starts. >> + * 1. During normal user application shutdown, vfio device state changes >> + * from _RUNNING to _STOP. This is optional, user application may or may not >> + * perform this state transition and vendor driver may not need. > > s/may not need/must not require, but must support this transition/ > >> + * 2. When user application save state or suspend application, device state >> + * transitions from _RUNNING to stop-and-copy state and then to _STOP. >> + * On state transition from _RUNNING to stop-and-copy, driver must >> + * stop device, save device state and send it to application through >> + * migration region. Sequence to be followed for such transition is given >> + * below. >> + * 3. In user application live migration, state transitions from _RUNNING >> + * to pre-copy to stop-and-copy to _STOP. >> + * On state transition from _RUNNING to pre-copy, driver should start >> + * gathering device state while application is still running and send device >> + * state data to application through migration region. >> + * On state transition from pre-copy to stop-and-copy, driver must stop >> + * device, save device state and send it to user application through >> + * migration region. >> + * Sequence to be followed for above two transitions is given below. > > Perhaps adding something like "Vendor drivers must support the pre-copy > state even for implementations where no data is provided to the user > until the stop-and-copy state. The user must not be required to > consume all migration data prior to transitioning to a new state, > including the stop-and-copy state." > >> + * 4. To start resuming phase, device state should be transitioned from >> + * _RUNNING to _RESUMING state. >> + * In _RESUMING state, driver should use received device state data through >> + * migration region to resume device. >> + * 5. On providing saved device data to driver, application should change state >> + * from _RESUMING to _RUNNING. >> + * >> + * pending bytes: (read only) >> + * Number of pending bytes yet to be migrated from vendor driver >> + * >> + * data_offset: (read only) >> + * User application should read data_offset in migration region from where >> + * user application should read device data during _SAVING state or write >> + * device data during _RESUMING state. See below for detail of sequence to >> + * be followed. >> + * >> + * data_size: (read/write) >> + * User application should read data_size to get size of data copied in >> + * bytes in migration region during _SAVING state and write size of data >> + * copied in bytes in migration region during _RESUMING state. >> + * >> + * Migration region looks like: >> + * ------------------------------------------------------------------ >> + * |vfio_device_migration_info| data section | >> + * | | /////////////////////////////// | >> + * ------------------------------------------------------------------ >> + * ^ ^ >> + * offset 0-trapped part data_offset >> + * >> + * Structure vfio_device_migration_info is always followed by data section in >> + * the region, so data_offset will always be non-0. Offset from where data is >> + * copied is decided by kernel driver, data section can be trapped or mapped >> + * or partitioned, depending on how kernel driver defines data section. >> + * Data section partition can be defined as mapped by sparse mmap capability. >> + * If mmapped, then data_offset should be page aligned, where as initial section >> + * which contain vfio_device_migration_info structure might not end at offset >> + * which is page aligned. The user is not required to access via mmap regardless >> + * of the region mmap capabilities. >> + * Vendor driver should decide whether to partition data section and how to >> + * partition the data section. Vendor driver should return data_offset >> + * accordingly. >> + * >> + * Sequence to be followed for _SAVING|_RUNNING device state or pre-copy phase >> + * and for _SAVING device state or stop-and-copy phase: >> + * a. read pending_bytes, indicates start of new iteration to get device data. >> + * Repeatative read on pending_bytes at this stage should have no side >> + * effect. > > s/Repeatative/Repeated/ > >> + * If pending_bytes == 0, user application should not iterate to get data >> + * for that device. >> + * If pending_bytes > 0, go through below steps. >> + * b. read data_offset, indicates vendor driver to make data available through >> + * data section. Vendor driver should return this read operation only after >> + * data is available from (region + data_offset) to (region + data_offset + >> + * data_size). >> + * c. read data_size, amount of data in bytes available through migration >> + * region. >> + * Read on data_offset and data_size should return offset and size of current >> + * buffer if user application reads those more than once here. >> + * d. read data of data_size bytes from (region + data_offset) from migration >> + * region. >> + * e. process data. >> + * f. read pending_bytes, this read operation indicates data from previous >> + * iteration had read. If pending_bytes > 0, goto step b. >> + * >> + * If there is any error during the above sequence, vendor driver can return >> + * error code for next read()/write() operation, that will terminate the loop >> + * and user should take next necessary action, for example, fail migration or >> + * terminate user application. >> + * >> + * User application can transition from _SAVING|_RUNNING (pre-copy state) to >> + * _SAVING (stop-and-copy) state regardless of pending bytes. > > Ok, you cover one of my concerns above here. Maybe doesn't hurt to > mention in both places. > >> + * User application should iterate in _SAVING (stop-and-copy) until >> + * pending_bytes is 0. >> + * >> + * Sequence to be followed while _RESUMING device state: >> + * While data for this device is available, repeat below steps: >> + * a. read data_offset from where user application should write data. >> + * b. write data of data_size to migration region from data_offset. Data size >> + * should be data packet size at source during _SAVING. > > I find the reference to data_size a bit confusing in this wording, > almost as if it's implied that the user reads data_size on the target. > What if we changed it a little: > > b. write migration data starting at migration region + data_offset for > length determined by data_size from the migration source. > >> + * c. write data_size which indicates vendor driver that data is written in >> + * migration region. Vendor driver should read this data from migration >> + * region and resume device's state. > > Perhaps "Vendor driver should apply the user provided migration region > data towards the device resume state"? > Ok. Updating as per all above comments. >> + * >> + * For user application, data is opaque. User application should write data in >> + * the same order as received and should of same transaction size at source. > > Great! > >> + */ >> + >> +struct vfio_device_migration_info { >> + __u32 device_state; /* VFIO device state */ >> +#define VFIO_DEVICE_STATE_STOP (0) >> +#define VFIO_DEVICE_STATE_RUNNING (1 << 0) >> +#define VFIO_DEVICE_STATE_SAVING (1 << 1) >> +#define VFIO_DEVICE_STATE_RESUMING (1 << 2) >> +#define VFIO_DEVICE_STATE_MASK (VFIO_DEVICE_STATE_RUNNING | \ >> + VFIO_DEVICE_STATE_SAVING | \ >> + VFIO_DEVICE_STATE_RESUMING) >> + >> +#define VFIO_DEVICE_STATE_VALID(state) \ >> + (state & VFIO_DEVICE_STATE_RESUMING ? \ >> + (state & VFIO_DEVICE_STATE_MASK) == VFIO_DEVICE_STATE_RESUMING : 1) >> + >> +#define VFIO_DEVICE_STATE_ERROR \ >> + (VFIO_DEVICE_STATE_SAVING | VFIO_DEVICE_STATE_RESUMING) > > It looks like this isn't used in this series, so I'm not sure the > intention of this macro, but I think we decided to only use 110b as the > "error" state. So should this be something like > > #define VFIO_DEVICE_STATE_IS_ERROR(state) \ > (state & VFIO_DEVICE_STATE_MASK == (VFIO_DEVICE_STATE_SAVING | \ > VFIO_DEVICE_STATE_RESUMING)) > > Or if this was intended to be used in setting the device_state to > error, perhaps > > #define VFIO_DEVICE_STATE_SET_ERROR(state) \ > ((state & ~VFIO_DEVICE_STATE_MASK) | VFIO_DEVICE_SATE_SAVING | \ > VFIO_DEVICE_STATE_RESUMING) This is also intended to to set device_state, vendor driver would set error state. Adding both above macros. >> + >> + __u32 reserved; > > Can we specify this reserved field as reads return zero, writes are > ignored so that we give ourselves the opportunity to re-purpose it > later? > > Ok. Adding Thanks, Kirti > + __u64 pending_bytes; >> + __u64 data_offset; >> + __u64 data_size; >> +} __attribute__((packed)); >> + >> /* >> * The MSIX mappable capability informs that MSIX data of a BAR can be mmapped >> * which allows direct access to non-MSIX registers which happened to be within > > Thanks, > Alex >