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Fri, 21 Jun 2024 16:54:56 +0000 (GMT) Received: from nasanex01b.na.qualcomm.com (nasanex01b.na.qualcomm.com [10.46.141.250]) by NASANPPMTA05.qualcomm.com (8.17.1.19/8.17.1.19) with ESMTPS id 45LGstRC028010 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 21 Jun 2024 16:54:55 GMT Received: from hu-eberman-lv.qualcomm.com (10.49.16.6) by nasanex01b.na.qualcomm.com (10.46.141.250) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.9; Fri, 21 Jun 2024 09:54:55 -0700 Date: Fri, 21 Jun 2024 09:54:54 -0700 From: Elliot Berman To: Fuad Tabba CC: David Hildenbrand , David Rientjes , Sean Christopherson , Jason Gunthorpe , John Hubbard , Andrew Morton , Shuah Khan , Matthew Wilcox , , , , , , , Subject: Re: [PATCH RFC 0/5] mm/gup: Introduce exclusive GUP pinning Message-ID: <20240621095319587-0700.eberman@hu-eberman-lv.qualcomm.com> References: <14bd145a-039f-4fb9-8598-384d6a051737@redhat.com> <20240619115135.GE2494510@nvidia.com> <4c8b81a0-3a76-4802-875f-f26ff1844955@redhat.com> <8e9436f2-6ebb-4ce1-a44f-2a941d354e2a@redhat.com> Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-ClientProxiedBy: nalasex01a.na.qualcomm.com (10.47.209.196) To nasanex01b.na.qualcomm.com (10.46.141.250) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-ORIG-GUID: QXDh3K7w48WsheqPI53a4Te-GVQCwGPf X-Proofpoint-GUID: QXDh3K7w48WsheqPI53a4Te-GVQCwGPf X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-06-21_08,2024-06-21_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 priorityscore=1501 bulkscore=0 mlxlogscore=708 lowpriorityscore=0 clxscore=1011 impostorscore=0 spamscore=0 mlxscore=0 adultscore=0 suspectscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2406140001 definitions=main-2406210122 On Fri, Jun 21, 2024 at 11:16:31AM +0100, Fuad Tabba wrote: > Hi David, > > On Fri, Jun 21, 2024 at 10:10 AM David Hildenbrand wrote: > > > > On 21.06.24 10:54, Fuad Tabba wrote: > > > Hi David, > > > > > > On Fri, Jun 21, 2024 at 9:44 AM David Hildenbrand wrote: > > >> > > >>>> Again from that thread, one of most important aspects guest_memfd is that VMAs > > >>>> are not required. Stating the obvious, lack of VMAs makes it really hard to drive > > >>>> swap, reclaim, migration, etc. from code that fundamentally operates on VMAs. > > >>>> > > >>>> : More broadly, no VMAs are required. The lack of stage-1 page tables are nice to > > >>>> : have; the lack of VMAs means that guest_memfd isn't playing second fiddle, e.g. > > >>>> : it's not subject to VMA protections, isn't restricted to host mapping size, etc. > > >>>> > > >>>> [1] https://lore.kernel.org/all/Zfmpby6i3PfBEcCV@google.com > > >>>> [2] https://lore.kernel.org/all/Zg3xF7dTtx6hbmZj@google.com > > >>> > > >>> I wonder if it might be more productive to also discuss this in one of > > >>> the PUCKs, ahead of LPC, in addition to trying to go over this in LPC. > > >> > > >> I don't know in which context you usually discuss that, but I could > > >> propose that as a topic in the bi-weekly MM meeting. > > >> > > >> This would, of course, be focused on the bigger MM picture: how to mmap, > > >> how how to support huge pages, interaction with page pinning, ... So > > >> obviously more MM focused once we are in agreement that we want to > > >> support shared memory in guest_memfd and how to make that work with core-mm. > > >> > > >> Discussing if we want shared memory in guest_memfd might be betetr > > >> suited for a different, more CC/KVM specific meeting (likely the "PUCKs" > > >> mentioned here?). > > > > > > Sorry, I should have given more context on what a PUCK* is :) It's a > > > periodic (almost weekly) upstream call for KVM. > > > > > > [*] https://lore.kernel.org/all/20230512231026.799267-1-seanjc@google.com/ > > > > > > But yes, having a discussion in one of the mm meetings ahead of LPC > > > would also be great. When do these meetings usually take place, to try > > > to coordinate across timezones. > > > > It's Wednesday, 9:00 - 10:00am PDT (GMT-7) every second week. > > > > If we're in agreement, we could (assuming there are no other planned > > topics) either use the slot next week (June 26) or the following one > > (July 10). > > > > Selfish as I am, I would prefer July 10, because I'll be on vacation > > next week and there would be little time to prepare. > > > > @David R., heads up that this might become a topic ("shared and private > > memory in guest_memfd: mmap, pinning and huge pages"), if people here > > agree that this is a direction worth heading. > > Thanks for the invite! Tentatively July 10th works for me, but I'd > like to talk to the others who might be interested (pKVM, Gunyah, and > others) to see if that works for them. I'll get back to you shortly. > I'd like to join too, July 10th at that time works for me. - Elliot