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AJvYcCW20VQF14OxvMSqvwb4RXHLfAGy0ac7/nocypItXOh4ilTXOamYiI/0CmnOJLD6bTBDBNkEUO2zNnozbwGhzPS5CEyl X-Gm-Message-State: AOJu0YwYH0zBeRecaKwVPnvfZpr3eo1pL4S0p817BfHr15kV5ATG4R0/ BoZ2n73/rrEP2MM/YSgfBf12eBpDpu+Wb/y3vz5NGKpDK/muS4bsMnwjSZ0/lrtgMIj4au2JPu1 oEg== X-Google-Smtp-Source: AGHT+IHDUra1AWqKgVEmx2cHjqVYae4a6BBkOB3zJOshknnYOHghCXWpyZttMxipDCeP9+v4upkb3HpjkA0= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a63:3d43:0:b0:71a:1f6f:1d0f with SMTP id 41be03b00d2f7-71b5c3db10amr16088a12.6.1719255786814; Mon, 24 Jun 2024 12:03:06 -0700 (PDT) Date: Mon, 24 Jun 2024 12:03:05 -0700 In-Reply-To: <20240621095319587-0700.eberman@hu-eberman-lv.qualcomm.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240619115135.GE2494510@nvidia.com> <4c8b81a0-3a76-4802-875f-f26ff1844955@redhat.com> <8e9436f2-6ebb-4ce1-a44f-2a941d354e2a@redhat.com> <20240621095319587-0700.eberman@hu-eberman-lv.qualcomm.com> Message-ID: Subject: Re: [PATCH RFC 0/5] mm/gup: Introduce exclusive GUP pinning From: Sean Christopherson To: Elliot Berman Cc: Fuad Tabba , David Hildenbrand , David Rientjes , Jason Gunthorpe , John Hubbard , Andrew Morton , Shuah Khan , Matthew Wilcox , maz@kernel.org, kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, pbonzini@redhat.com Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable On Fri, Jun 21, 2024, Elliot Berman wrote: > On Fri, Jun 21, 2024 at 11:16:31AM +0100, Fuad Tabba wrote: > > On Fri, Jun 21, 2024 at 10:10=E2=80=AFAM David Hildenbrand wrote: > > > On 21.06.24 10:54, Fuad Tabba wrote: > > > > On Fri, Jun 21, 2024 at 9:44=E2=80=AFAM David Hildenbrand wrote: > > > >> > > > >>>> Again from that thread, one of most important aspects guest_memf= d is that VMAs > > > >>>> are not required. Stating the obvious, lack of VMAs makes it re= ally hard to drive > > > >>>> swap, reclaim, migration, etc. from code that fundamentally oper= ates on VMAs. > > > >>>> > > > >>>> : More broadly, no VMAs are required. The lack of stage-1 pa= ge 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 ho= st 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 o= ne 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 cou= ld > > > >> 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 wit= h 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@goog= le.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. Let's do the MM meeting. As evidenced by the responses, it'll be easier to= get KVM folks to join the MM meeting as opposed to other way around. > > > 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 priva= te > > > memory in guest_memfd: mmap, pinning and huge pages"), if people here > > > agree that this is a direction worth heading. > >=20 > > 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. > >=20 >=20 > I'd like to join too, July 10th at that time works for me. July 10th works for me too.