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Sun, 19 Jul 2020 01:47:54 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserp3030.oracle.com with ESMTP id 32canj2wcp-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sun, 19 Jul 2020 01:47:54 +0000 Received: from abhmp0019.oracle.com (abhmp0019.oracle.com [141.146.116.25]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 06J1lAXW028549; Sun, 19 Jul 2020 01:47:14 GMT Received: from [10.39.198.189] (/10.39.198.189) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Sun, 19 Jul 2020 01:47:09 +0000 Subject: Re: [PATCH v2 01/11] xen/manage: keep track of the on-going suspend mode To: Anchal Agarwal Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, jgross@suse.com, linux-pm@vger.kernel.org, linux-mm@kvack.org, kamatam@amazon.com, sstabellini@kernel.org, konrad.wilk@oracle.com, roger.pau@citrix.com, axboe@kernel.dk, davem@davemloft.net, rjw@rjwysocki.net, len.brown@intel.com, pavel@ucw.cz, peterz@infradead.org, eduval@amazon.com, sblbir@amazon.com, xen-devel@lists.xenproject.org, vkuznets@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, dwmw@amazon.co.uk, benh@kernel.crashing.org References: <20200702182136.GA3511@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> <50298859-0d0e-6eb0-029b-30df2a4ecd63@oracle.com> <20200715204943.GB17938@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> <0ca3c501-e69a-d2c9-a24c-f83afd4bdb8c@oracle.com> <20200717191009.GA3387@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> From: Boris Ostrovsky Autocrypt: addr=boris.ostrovsky@oracle.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200717191009.GA3387@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9686 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=100 suspectscore=0 malwarescore=0 phishscore=0 spamscore=100 mlxscore=100 bulkscore=0 adultscore=0 mlxlogscore=-1000 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007190011 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9686 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=100 malwarescore=0 bulkscore=0 spamscore=100 impostorscore=0 suspectscore=0 adultscore=0 clxscore=1015 mlxlogscore=-1000 priorityscore=1501 phishscore=0 lowpriorityscore=0 mlxscore=100 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007190010 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (Roger, question for you at the very end) On 7/17/20 3:10 PM, Anchal Agarwal wrote: > On Wed, Jul 15, 2020 at 05:18:08PM -0400, Boris Ostrovsky wrote: >> CAUTION: This email originated from outside of the organization. Do no= t click links or open attachments unless you can confirm the sender and k= now the content is safe. >> >> >> >> On 7/15/20 4:49 PM, Anchal Agarwal wrote: >>> On Mon, Jul 13, 2020 at 11:52:01AM -0400, Boris Ostrovsky wrote: >>>> CAUTION: This email originated from outside of the organization. Do = not click links or open attachments unless you can confirm the sender and= know the content is safe. >>>> >>>> >>>> >>>> On 7/2/20 2:21 PM, Anchal Agarwal wrote: >>>>> + >>>>> +bool xen_is_xen_suspend(void) >>>> Weren't you going to call this pv suspend? (And also --- is this sus= pend >>>> or hibernation? Your commit messages and cover letter talk about fix= ing >>>> hibernation). >>>> >>>> >>> This is for hibernation is for pvhvm/hvm/pv-on-hvm guests as you may = call it. >>> The method is just there to check if "xen suspend" is in progress. >>> I do not see "xen_suspend" differentiating between pv or hvm >>> domain until later in the code hence, I abstracted it to xen_is_xen_s= uspend. >> >> I meant "pv suspend" in the sense that this is paravirtual suspend, no= t >> suspend for paravirtual guests. Just like pv drivers are for both pv a= nd >> hvm guests. >> >> >> And then --- should it be pv suspend or pv hibernation? >> >> > Ok so I think I am lot confused by this question. Here is what this > function for, function xen_is_xen_suspend() just tells us whether=20 > the guest is in "SHUTDOWN_SUSPEND" state or not. This check is needed > for correct invocation of syscore_ops callbacks registered for guest's > hibernation and for xenbus to invoke respective callbacks[suspend/resum= e > vs freeze/thaw/restore]. > Since "shutting_down" state is defined static and is not directly avail= able > to other parts of the code, the function solves the purpose. > > I am having hard time understanding why this should be called pv > suspend/hibernation unless you are suggesting something else? > Am I missing your point here?=20 I think I understand now what you are trying to say --- it's whether we are going to use xen_suspend() routine, right? If that's the case then sure, you can use "xen_suspend" term. (I'd probably still change xen_is_xen_suspend() to is_xen_suspend()) >>>>> +{ >>>>> + return suspend_mode =3D=3D XEN_SUSPEND; >>>>> +} >>>>> + >>>> +static int xen_setup_pm_notifier(void) >>>> +{ >>>> + if (!xen_hvm_domain()) >>>> + return -ENODEV; >>>> >>>> I forgot --- what did we decide about non-x86 (i.e. ARM)? >>> It would be great to support that however, its out of >>> scope for this patch set. >>> I=E2=80=99ll be happy to discuss it separately. >> >> I wasn't implying that this *should* work on ARM but rather whether th= is >> will break ARM somehow (because xen_hvm_domain() is true there). >> >> > Ok makes sense. TBH, I haven't tested this part of code on ARM and the = series > was only support x86 guests hibernation. > Moreover, this notifier is there to distinguish between 2 PM > events PM SUSPEND and PM hibernation. Now since we only care about PM > HIBERNATION I may just remove this code and rely on "SHUTDOWN_SUSPEND" = state. > However, I may have to fix other patches in the series where this check= may > appear and cater it only for x86 right? I don't know what would happen if ARM guest tries to handle hibernation callbacks. The only ones that you are introducing are in block and net fronts and that's arch-independent. You do add a bunch of x86-specific code though (syscore ops), would something similar be needed for ARM? >>>> And PVH dom0. >>> That's another good use case to make it work with however, I still >>> think that should be tested/worked upon separately as the feature its= elf >>> (PVH Dom0) is very new. >> >> Same question here --- will this break PVH dom0? >> > I haven't tested it as a part of this series. Is that a blocker here? I suspect dom0 will not do well now as far as hibernation goes, in which case you are not breaking anything. Roger? -boris