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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <07E9FD5B-F07F-415B-9C00-A2A882F07CBC@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-07-13_07:2020-07-13, 2020-07-13 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 priorityscore=1501 clxscore=1015 phishscore=0 mlxscore=0 spamscore=0 bulkscore=0 impostorscore=0 mlxlogscore=999 lowpriorityscore=0 malwarescore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007130080 Received-SPF: pass client-ip=148.163.156.1; envelope-from=borntraeger@de.ibm.com; helo=mx0a-001b2d01.pphosted.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/13 07:08:27 X-ACL-Warn: Detected OS = Linux 3.x [generic] [fuzzy] X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-1, 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: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Thomas Huth , Janosch Frank , "Michael S . Tsirkin" , Cornelia Huck , qemu-devel@nongnu.org, Halil Pasic , qemu-s390x@nongnu.org, Claudio Imbrenda , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 13.07.20 12:27, David Hildenbrand wrote: > > >> Am 13.07.2020 um 11:12 schrieb Heiko Carstens : >> >> On Fri, Jul 10, 2020 at 05:24:07PM +0200, David Hildenbrand wrote: >>>> On 10.07.20 17:18, Heiko Carstens wrote: >>>> On Fri, Jul 10, 2020 at 02:12:33PM +0200, David Hildenbrand wrote: >>>>>> Note: Reading about diag260 subcode 0xc, we could modify Linux to query >>>>>> the maximum possible pfn via diag260 0xc. Then, we maybe could avoid >>>>>> indicating maxram size via SCLP, and keep diag260-unaware OSs keep >>>>>> working as before. Thoughts? >>>>> >>>>> Implemented it, seems to work fine. >>>> >>>> The returned value would not include standby/reserved memory within >>>> z/VM. So this seems not to work. >>> >>> Which value exactly are you referencing? diag 0xc returns two values. >>> One of them seems to do exactly what we need. >>> >>> See >>> https://github.com/davidhildenbrand/linux/commit/a235f9fb20df7c04ae89bc0d134332d1a01842c7 >>> >>> for my current Linux approach. >>> >>>> Also: why do you want to change this >>> >>> Which change exactly do you mean? >>> >>> If we limit the value returned via SCLP to initial memory, we cannot >>> break any guest (e.g., Linux pre 4.2, kvm-unit-tests). diag260 is then >>> purely optional. >> >> Ok, now I see the context. Christian added my just to cc on this >> specific patch. > > I tried to Cc you an all patches but the mail bounced with unknown address (maybe I messed up). > >> So if I understand you correctly, then you want to use diag 260 in >> order to figure out how much memory is _potentially_ available for a >> guest? > > Yes, exactly. > >> >> This does not fit to the current semantics, since diag 260 returns the >> address of the highest *currently* accessible address. That is: it >> does explicitly *not* include standby memory or anything else that >> might potentially be there. > > The confusing part is that it talks about „adressible“ and not „accessible“. Now that I understood the „DEFINE STORAGE ...“ example, it makes sense that the values change with reserved/standby memory. > > I agree that reusing that interface might not be what we want. I just seemed too easy to avoid creating something new :) > >> >> So you would need a different interface to tell the guest about your >> new hotplug memory interface. If sclp does not work, then maybe a new >> diagnose(?). >> > > Yes, I think a new Diagnose makes sense. I‘ll have a look next week to figure out which codes/subcodes we could use. @Christian @Conny any ideas/pointers?> Wouldnt sclp be the right thing to provide the max increment number? (and thus the max memory address) And then (when I got the discussion right) use diag 260 to get the _current_ value.