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Mon, 28 Sep 2020 18:50:23 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by aserp3020.oracle.com with ESMTP id 33tfhwmm91-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 28 Sep 2020 18:50:23 +0000 Received: from abhmp0007.oracle.com (abhmp0007.oracle.com [141.146.116.13]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 08SIo1mj032727; Mon, 28 Sep 2020 18:50:01 GMT Received: from [10.74.86.78] (/10.74.86.78) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 28 Sep 2020 11:50:01 -0700 Subject: Re: [PATCH v3 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: <4b2bbc8b-7817-271a-4ff0-5ee5df956049@oracle.com> <20200914214754.GA19975@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> <20200915180055.GB19975@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> <5f1e4772-7bd9-e6c0-3fe6-eef98bb72bd8@oracle.com> <20200921215447.GA28503@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> <20200922231736.GA24215@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> <20200925190423.GA31885@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> <274ddc57-5c98-5003-c850-411eed1aea4c@oracle.com> <20200925222826.GA11755@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> From: boris.ostrovsky@oracle.com Organization: Oracle Corporation Message-ID: Date: Mon, 28 Sep 2020 14:49:56 -0400 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.2.2 MIME-Version: 1.0 In-Reply-To: <20200925222826.GA11755@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9758 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 mlxlogscore=999 bulkscore=0 phishscore=0 malwarescore=0 adultscore=0 suspectscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009280143 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9758 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 mlxscore=0 phishscore=0 suspectscore=0 mlxlogscore=999 clxscore=1015 priorityscore=1501 impostorscore=0 lowpriorityscore=0 bulkscore=0 spamscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009280143 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/25/20 6:28 PM, Anchal Agarwal wrote: > On Fri, Sep 25, 2020 at 04:02:58PM -0400, boris.ostrovsky@oracle.com 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 9/25/20 3:04 PM, Anchal Agarwal wrote: >>> On Tue, Sep 22, 2020 at 11:17:36PM +0000, Anchal Agarwal wrote: >>>> On Tue, Sep 22, 2020 at 12:18:05PM -0400, boris.ostrovsky@oracle.com 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 9/21/20 5:54 PM, Anchal Agarwal wrote: >>>>> Also, wrt KASLR stuff, that issue is still seen sometimes but I haven't had >>>>> bandwidth to dive deep into the issue and fix it. >> >> So what's the plan there? You first mentioned this issue early this year and judged by your response it is not clear whether you will ever spend time looking at it. >> > I do want to fix it and did do some debugging earlier this year just haven't > gotten back to it. Also, wanted to understand if the issue is a blocker to this > series? Integrating code with known bugs is less than ideal. 3% failure for this feature seems to be a manageable number from the reproducability perspective --- you should be able to script this and each iteration should take way under a minute, no? > I had some theories when debugging around this like if the random base address picked by kaslr for the > resuming kernel mismatches the suspended kernel and just jogging my memory, I didn't find that as the case. > Another hunch was if physical address of registered vcpu info at boot is different from what suspended kernel > has and that can cause CPU's to get stuck when coming online. I'd think if this were the case you'd have 100% failure rate. And we are also re-registering vcpu info on xen restore and I am not aware of any failures due to KASLR. > The issue was only > reproducible 3% of the time out of 3000 runs hence its hard to just reproduce this. > > Moreover, I also wanted to get an insight on if hibernation works correctly with KASLR > generally and its only Xen causing the issue? With KASLR being on by default I'd be surprised if it didn't. -boris