From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=OdKR=D6=nongnu.org=qemu-devel-bounces+qemu-devel=archiver.kernel.org@kernel.org>
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=-11.2 required=3.0 tests=BAYES_00,DKIM_INVALID,
	DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,
	NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,
	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 9FE69C5517A
	for <qemu-devel@archiver.kernel.org>; Fri, 23 Oct 2020 07:19:21 +0000 (UTC)
Received: from lists.gnu.org (lists.gnu.org [209.51.188.17])
	(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 0314721527
	for <qemu-devel@archiver.kernel.org>; Fri, 23 Oct 2020 07:19:20 +0000 (UTC)
Authentication-Results: mail.kernel.org;
	dkim=fail reason="signature verification failed" (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="DjH1Cfmk"
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0314721527
Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=nvidia.com
Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org
Received: from localhost ([::1]:59014 helo=lists1p.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.90_1)
	(envelope-from <qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org>)
	id 1kVrM7-0001ok-WB
	for qemu-devel@archiver.kernel.org; Fri, 23 Oct 2020 03:19:20 -0400
Received: from eggs.gnu.org ([2001:470:142:3::10]:60484)
 by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)
 (Exim 4.90_1) (envelope-from <kwankhede@nvidia.com>)
 id 1kVrFm-0003jR-LT
 for qemu-devel@nongnu.org; Fri, 23 Oct 2020 03:12:46 -0400
Received: from hqnvemgate26.nvidia.com ([216.228.121.65]:5742)
 by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)
 (Exim 4.90_1) (envelope-from <kwankhede@nvidia.com>)
 id 1kVrFj-0004Ti-IL
 for qemu-devel@nongnu.org; Fri, 23 Oct 2020 03:12:46 -0400
Received: from hqmail.nvidia.com (Not Verified[216.228.121.13]) by
 hqnvemgate26.nvidia.com (using TLS: TLSv1.2, AES256-SHA)
 id <B5f92825d0000>; Fri, 23 Oct 2020 00:12:29 -0700
Received: from [10.40.101.194] (10.124.1.5) by HQMAIL107.nvidia.com
 (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Fri, 23 Oct
 2020 07:12:23 +0000
Subject: Re: [PATCH v27 07/17] vfio: Register SaveVMHandlers for VFIO device
To: Alex Williamson <alex.williamson@redhat.com>, <dgilbert@redhat.com>
References: <1603365127-14202-1-git-send-email-kwankhede@nvidia.com>
 <1603365127-14202-8-git-send-email-kwankhede@nvidia.com>
 <20201022125108.6137e462@w520.home>
X-Nvconfidentiality: public
From: Kirti Wankhede <kwankhede@nvidia.com>
Message-ID: <bc0de965-31ce-069a-9473-2fbae0157c86@nvidia.com>
Date: Fri, 23 Oct 2020 12:42:19 +0530
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101
 Thunderbird/68.12.1
MIME-Version: 1.0
In-Reply-To: <20201022125108.6137e462@w520.home>
Content-Type: text/plain; charset="utf-8"; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
X-Originating-IP: [10.124.1.5]
X-ClientProxiedBy: HQMAIL105.nvidia.com (172.20.187.12) To
 HQMAIL107.nvidia.com (172.20.187.13)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1;
 t=1603437149; bh=XTcpkukgftBgyVVRmkDVLtr564A1TxPXOYzAzRTrZxU=;
 h=Subject:To:CC:References:X-Nvconfidentiality:From:Message-ID:Date:
 User-Agent:MIME-Version:In-Reply-To:Content-Type:Content-Language:
 Content-Transfer-Encoding:X-Originating-IP:X-ClientProxiedBy;
 b=DjH1CfmkSMBS7sFiwrUQb48QyGrlxANinrGLpUdy25HV6d4lpq++u4zHMJe3szOkn
 elRA70i5/UxuPrA9w6lvzflhPdViy33UCCY9bmzguI67jqOS0ZG62jlSiOnmu03eSr
 Il3Fkt/1YzL91VdInTVEJmV//nHfxHrXRmasrANS51HUKkxxY/aZw06ZHUF7OQ/T/q
 Stvg8E5gh9DfLUWmyUbKIfr2Ml+Y/FFScSIclhS7mOQcJQmtEBoyJvHKIEykObzIyF
 1R8YYoMH+wOAopav/3YHb8j2A/ktnu4ERpjSb70VUJakMAswzIWOyhNX/0IztO9dc0
 YXnKJGny9kBng==
Received-SPF: pass client-ip=216.228.121.65; envelope-from=kwankhede@nvidia.com;
 helo=hqnvemgate26.nvidia.com
X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/23 03:12:41
X-ACL-Warn: Detected OS   = Windows 7 or 8 [fuzzy]
X-Spam_score_int: -71
X-Spam_score: -7.2
X-Spam_bar: -------
X-Spam_report: (-7.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001,
 DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,
 NICE_REPLY_A=-0.107, RCVD_IN_DNSWL_HI=-5, 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: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
 <mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <https://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
 <mailto:qemu-devel-request@nongnu.org?subject=subscribe>
Cc: cjia@nvidia.com, zhi.wang.linux@gmail.com, aik@ozlabs.ru,
 Zhengxiao.zx@Alibaba-inc.com, shuangtai.tst@alibaba-inc.com,
 qemu-devel@nongnu.org, peterx@redhat.com, eauger@redhat.com,
 yi.l.liu@intel.com, quintela@redhat.com, ziye.yang@intel.com,
 armbru@redhat.com, mlevitsk@redhat.com, pasic@linux.ibm.com,
 felipe@nutanix.com, zhi.a.wang@intel.com, mcrossley@nvidia.com,
 kevin.tian@intel.com, yan.y.zhao@intel.com, eskultet@redhat.com,
 changpeng.liu@intel.com, cohuck@redhat.com, Ken.Xue@amd.com,
 jonathan.davies@nutanix.com, pbonzini@redhat.com, dnigam@nvidia.com
Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org
Sender: "Qemu-devel"
 <qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org>



On 10/23/2020 12:21 AM, Alex Williamson wrote:
> On Thu, 22 Oct 2020 16:41:57 +0530
> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> 
>> Define flags to be used as delimiter in migration stream for VFIO devices.
>> Added .save_setup and .save_cleanup functions. Map & unmap migration
>> region from these functions at source during saving or pre-copy phase.
>>
>> Set VFIO device state depending on VM's state. During live migration, VM is
>> running when .save_setup is called, _SAVING | _RUNNING state is set for VFIO
>> device. During save-restore, VM is paused, _SAVING state is set for VFIO device.
>>
>> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
>> Reviewed-by: Neo Jia <cjia@nvidia.com>
>> ---
>>   hw/vfio/migration.c  | 96 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>>   hw/vfio/trace-events |  2 ++
>>   2 files changed, 98 insertions(+)
>>
>> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
>> index 7c4fa0d08ea6..2e1054bf7f43 100644
>> --- a/hw/vfio/migration.c
>> +++ b/hw/vfio/migration.c
>> @@ -8,12 +8,15 @@
>>    */
>>   
>>   #include "qemu/osdep.h"
>> +#include "qemu/main-loop.h"
>> +#include "qemu/cutils.h"
>>   #include <linux/vfio.h>
>>   
>>   #include "sysemu/runstate.h"
>>   #include "hw/vfio/vfio-common.h"
>>   #include "cpu.h"
>>   #include "migration/migration.h"
>> +#include "migration/vmstate.h"
>>   #include "migration/qemu-file.h"
>>   #include "migration/register.h"
>>   #include "migration/blocker.h"
>> @@ -25,6 +28,22 @@
>>   #include "trace.h"
>>   #include "hw/hw.h"
>>   
>> +/*
>> + * Flags to be used as unique delimiters for VFIO devices in the migration
>> + * stream. These flags are composed as:
>> + * 0xffffffff => MSB 32-bit all 1s
>> + * 0xef10     => Magic ID, represents emulated (virtual) function IO
>> + * 0x0000     => 16-bits reserved for flags
>> + *
>> + * The beginning of state information is marked by _DEV_CONFIG_STATE,
>> + * _DEV_SETUP_STATE, or _DEV_DATA_STATE, respectively. The end of a
>> + * certain state information is marked by _END_OF_STATE.
>> + */
>> +#define VFIO_MIG_FLAG_END_OF_STATE      (0xffffffffef100001ULL)
>> +#define VFIO_MIG_FLAG_DEV_CONFIG_STATE  (0xffffffffef100002ULL)
>> +#define VFIO_MIG_FLAG_DEV_SETUP_STATE   (0xffffffffef100003ULL)
>> +#define VFIO_MIG_FLAG_DEV_DATA_STATE    (0xffffffffef100004ULL)
>> +
>>   static inline int vfio_mig_access(VFIODevice *vbasedev, void *val, int count,
>>                                     off_t off, bool iswrite)
>>   {
>> @@ -129,6 +148,69 @@ static int vfio_migration_set_state(VFIODevice *vbasedev, uint32_t mask,
>>       return 0;
>>   }
>>   
>> +/* ---------------------------------------------------------------------- */
>> +
>> +static int vfio_save_setup(QEMUFile *f, void *opaque)
>> +{
>> +    VFIODevice *vbasedev = opaque;
>> +    VFIOMigration *migration = vbasedev->migration;
>> +    int ret;
>> +
>> +    trace_vfio_save_setup(vbasedev->name);
>> +
>> +    qemu_put_be64(f, VFIO_MIG_FLAG_DEV_SETUP_STATE);
>> +
>> +    if (migration->region.mmaps) {
>> +        /*
>> +         * vfio_region_mmap() called from migration thread. Memory API called
>> +         * from vfio_regio_mmap() need it when called from outdide the main loop
>> +         * thread.
>> +         */
> 
> Thanks for adding this detail, maybe refine slightly as:
> 
>    Calling vfio_region_mmap() from migration thread.  Memory APIs called
>    from this function require locking the iothread when called from
>    outside the main loop thread.
> 
> Does that capture the intent?
> 

Ok.

>> +        qemu_mutex_lock_iothread();
>> +        ret = vfio_region_mmap(&migration->region);
>> +        qemu_mutex_unlock_iothread();
>> +        if (ret) {
>> +            error_report("%s: Failed to mmap VFIO migration region: %s",
>> +                         vbasedev->name, strerror(-ret));
>> +            error_report("%s: Falling back to slow path", vbasedev->name);
>> +        }
>> +    }
>> +
>> +    ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_MASK,
>> +                                   VFIO_DEVICE_STATE_SAVING);
>> +    if (ret) {
>> +        error_report("%s: Failed to set state SAVING", vbasedev->name);
>> +        return ret;
>> +    }
>> +
>> +    qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
>> +
>> +    ret = qemu_file_get_error(f);
>> +    if (ret) {
>> +        return ret;
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>> +static void vfio_save_cleanup(void *opaque)
>> +{
>> +    VFIODevice *vbasedev = opaque;
>> +    VFIOMigration *migration = vbasedev->migration;
>> +
>> +    if (migration->region.mmaps) {
>> +        vfio_region_unmap(&migration->region);
>> +    }
> 
> 
> Are we in a different thread context here that we don't need that same
> iothread locking?
> 

qemu_savevm_state_setup() is called without holding iothread lock and 
qemu_savevm_state_cleanup() is called holding iothread lock, so we don't 
need lock here.

> 
>> +    trace_vfio_save_cleanup(vbasedev->name);
>> +}
>> +
>> +static SaveVMHandlers savevm_vfio_handlers = {
>> +    .save_setup = vfio_save_setup,
>> +    .save_cleanup = vfio_save_cleanup,
>> +};
>> +
>> +/* ---------------------------------------------------------------------- */
>> +
>>   static void vfio_vmstate_change(void *opaque, int running, RunState state)
>>   {
>>       VFIODevice *vbasedev = opaque;
>> @@ -219,6 +301,8 @@ static int vfio_migration_init(VFIODevice *vbasedev,
>>       int ret;
>>       Object *obj;
>>       VFIOMigration *migration;
>> +    char id[256] = "";
>> +    g_autofree char *path = NULL, *oid;
> 
> 
> AIUI, oid must also be initialized as a g_autofree variable.
> 
>>   
>>       if (!vbasedev->ops->vfio_get_object) {
>>           return -EINVAL;
>> @@ -248,6 +332,18 @@ static int vfio_migration_init(VFIODevice *vbasedev,
>>   
>>       vbasedev->migration = migration;
>>       migration->vbasedev = vbasedev;
>> +
>> +    oid = vmstate_if_get_id(VMSTATE_IF(DEVICE(obj)));
>> +    if (oid) {
>> +        path = g_strdup_printf("%s/vfio", oid);
>> +    } else {
>> +        path = g_strdup("vfio");
> 
> 
> If we get here then all vfio devices have the same id string.  Isn't
> that a problem?  Thanks,
> 

Most of the bus types has get_dev_path() callback implemented which is 
called from get_id, so there are very less chance to get here.
With above change, id string we get looks like '0000:00:04.0/vfio', 
trace logs below:
qemu_loadvm_state_section_startfull 61.942 pid=625231 section_id=0x2f 
idstr=b'0000:00:04.0/vfio' instance_id=0x0 version_id=0x1

qemu_loadvm_state_section_startfull 1.242 pid=625231 section_id=0x30 
idstr=b'0000:00:05.0/vfio' instance_id=0x0 version_id=0x1

where '0000:00:04.0'shows location within guest, so that it gets 
preserved and used during resume.

In the worst when it is not present, idstr remains same but instance_id 
changes:

qemu_loadvm_state_section_startfull 54.931 pid=609474 section_id=0x2f 
idstr=b'vfio' instance_id=0x0 version_id=0x1

qemu_loadvm_state_section_startfull 1.180 pid=609474 section_id=0x30 
idstr=b'vfio' instance_id=0x1 version_id=0x1

But there is no other way to know location of the device within guest.

Dave, any suggestions here?

Thanks,
Kirti


> Alex
> 
> 
>> +    }
>> +    strpadcpy(id, sizeof(id), path, '\0');
>> +
>> +    register_savevm_live(id, VMSTATE_INSTANCE_ID_ANY, 1, &savevm_vfio_handlers,
>> +                         vbasedev);
>> +
>>       migration->vm_state = qemu_add_vm_change_state_handler(vfio_vmstate_change,
>>                                                             vbasedev);
>>       migration->migration_state.notify = vfio_migration_state_notifier;
>> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
>> index 78d7d83b5ef8..f148b5e828c1 100644
>> --- a/hw/vfio/trace-events
>> +++ b/hw/vfio/trace-events
>> @@ -151,3 +151,5 @@ vfio_migration_probe(const char *name, uint32_t index) " (%s) Region %d"
>>   vfio_migration_set_state(const char *name, uint32_t state) " (%s) state %d"
>>   vfio_vmstate_change(const char *name, int running, const char *reason, uint32_t dev_state) " (%s) running %d reason %s device state %d"
>>   vfio_migration_state_notifier(const char *name, const char *state) " (%s) state %s"
>> +vfio_save_setup(const char *name) " (%s)"
>> +vfio_save_cleanup(const char *name) " (%s)"
> 
>