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Thu, 1 Oct 2020 12:44:05 GMT Received: from [10.74.86.152] (/10.74.86.152) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 01 Oct 2020 05:44:04 -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: <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> <20200930212944.GA3138@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> From: boris.ostrovsky@oracle.com Organization: Oracle Corporation Message-ID: <8cd59d9c-36b1-21cf-e59f-40c5c20c65f8@oracle.com> Date: Thu, 1 Oct 2020 08:43:58 -0400 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.3.1 MIME-Version: 1.0 In-Reply-To: <20200930212944.GA3138@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=9760 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 spamscore=0 mlxscore=0 phishscore=0 adultscore=0 bulkscore=0 mlxlogscore=980 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2010010109 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9760 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 mlxscore=0 phishscore=0 suspectscore=0 mlxlogscore=979 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-2010010110 >>>>>>> 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. >> > So for this series to be accepted, KASLR needs to be fixed along with other > comments of course? Yes, please. >>> 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. >> > What I meant there wrt VCPU info was that VCPU info is not unregistered during hibernation, > so Xen still remembers the old physical addresses for the VCPU information, created by the > booting kernel. But since the hibernation kernel may have different physical > addresses for VCPU info and if mismatch happens, it may cause issues with resume. > During hibernation, the VCPU info register hypercall is not invoked again. I still don't think that's the cause but it's certainly worth having a look. -boris