From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sean Christopherson Date: Fri, 3 Nov 2023 16:17:23 -0700 Subject: [PATCH v13 16/35] KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory In-Reply-To: References: <20231027182217.3615211-1-seanjc@google.com> <20231027182217.3615211-17-seanjc@google.com> Message-ID: List-Id: To: kvm-riscv@lists.infradead.org MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Thu, Nov 02, 2023, Fuad Tabba wrote: > On Wed, Nov 1, 2023 at 9:55?PM Sean Christopherson wrote: > > E.g. a misbehaving userspace could prematurely delete a memslot. And the more > > fun example is intrahost migration, where the plan is to allow pointing multiple > > guest_memfd files at a single guest_memfd inode: > > https://lore.kernel.org/all/cover.1691446946.git.ackerleytng at google.com > > > > There was a lot of discussion for this, but it's scattered all over the place. > > The TL;DR is is that the inode will represent physical memory, and a file will > > represent a given "struct kvm" instance's view of that memory. And so the memory > > isn't reclaimed until the inode is truncated/punched. > > > > I _think_ this reflects the most recent plan from the guest_memfd side: > > https://lore.kernel.org/all/1233d749211c08d51f9ca5d427938d47f008af1f.1689893403.git.isaku.yamahata at intel.com Doh, sitting in my TODO folder... https://lore.kernel.org/all/20231016115028.996656-1-michael.roth at amd.com > Thanks for pointing that out. I think this might be the way to go. > I'll have a closer look at this and see how to get it to work with > pKVM. From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yw1-f201.google.com (mail-yw1-f201.google.com [209.85.128.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 05477F9E7 for ; Fri, 3 Nov 2023 23:17:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="GbbjB2Oq" Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-5b31e000e97so36317827b3.1 for ; Fri, 03 Nov 2023 16:17:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1699053445; x=1699658245; darn=lists.linux.dev; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:from:to:cc:subject:date:message-id :reply-to; bh=wL2niLMenc8rXWamhCVdrH1GL3hMVyvGfUspx7X4DS0=; b=GbbjB2OqMSQ0n/lCTpDdY5BtncZxwuckpE/m/pEdm+n/MmANGJRkLiqC9ERMRgWr4t AflLSgP0Qkywl4M+SzeNaeYTrvh50u06wsqwifZhwnZ84rF0+vTJ/VS9mDGR5XT28QeN iWzJWg50mRoDjhNPYFIqiocY7yMXcS5rMrrGEH+6INBJX6UpJkYXlufCtxwHV7H895DA qDdbL5dnFZqvXBohZF/G6UljSzA1oNuLqZ7kJTZELOtslpM2o3cOdnGNPmTIvfRdAcMW uSsswPBbAcVL2r8rpE4yP6dp+HChkaaHrQ7Mq1ZVOCzhd8Wd7n272Z8qVisom1m+wlQl nGlg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1699053445; x=1699658245; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=wL2niLMenc8rXWamhCVdrH1GL3hMVyvGfUspx7X4DS0=; b=bjs1oEVV8Way0y4DkqKkFHumrXkR1wW4aIc/oi00Zfzy/8h+0s2X96JT4PSPyXaGnX Ss30GE6wxNDJ0YqjfCdh4l42ELB2ntpKHG9/v+o0D2vDf03P3bLKv5pTMS3pbFJU1yZ9 cYSve1ckQI+eMkBHLeGnEjfs3lJ/21/Z1ACvDBGLVpk4ZFejFXWth8nTHBZv/J9JrfEn tJ/xswnCfUHl8DHWhJVOO7SiOnPefPxoen1BCXY3beE9YVYJUnIySAEXrzWSC4iK4dvp he99ERUzXKWd6HenTScGorYEGvfH3juZriZIi8uCPB3UAd9S2///iyRLV0FLPG8dpT0D rIsQ== X-Gm-Message-State: AOJu0YxhSZG1i1qC+FkMoH/Gd/jeW1ww10SysTr4HpeuDqbL1TbsN5Ib ex2NZ71RcZIcpcJ17q7aefRky9GuqMc= X-Google-Smtp-Source: AGHT+IGJDyi83TwJx+I35GsLQytKZmA4RJCyClEGAPsqdhhOEgS+Lm1oHaoRVNSHVuwQA3+7WVp40Ul4xUY= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a81:4958:0:b0:59f:3cde:b33a with SMTP id w85-20020a814958000000b0059f3cdeb33amr84737ywa.6.1699053444944; Fri, 03 Nov 2023 16:17:24 -0700 (PDT) Date: Fri, 3 Nov 2023 16:17:23 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231027182217.3615211-1-seanjc@google.com> <20231027182217.3615211-17-seanjc@google.com> Message-ID: Subject: Re: [PATCH v13 16/35] KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory From: Sean Christopherson To: Fuad Tabba Cc: Paolo Bonzini , Marc Zyngier , Oliver Upton , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexander Viro , Christian Brauner , "Matthew Wilcox (Oracle)" , Andrew Morton , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Xiaoyao Li , Xu Yilun , Chao Peng , Jarkko Sakkinen , Anish Moorthy , David Matlack , Yu Zhang , Isaku Yamahata , "=?utf-8?Q?Micka=C3=ABl_Sala=C3=BCn?=" , Vlastimil Babka , Vishal Annapurve , Ackerley Tng , Maciej Szmigiero , David Hildenbrand , Quentin Perret , Michael Roth , Wang , Liam Merwick , Isaku Yamahata , "Kirill A . Shutemov" Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable On Thu, Nov 02, 2023, Fuad Tabba wrote: > On Wed, Nov 1, 2023 at 9:55=E2=80=AFPM Sean Christopherson wrote: > > E.g. a misbehaving userspace could prematurely delete a memslot. And t= he more > > fun example is intrahost migration, where the plan is to allow pointing= multiple > > guest_memfd files at a single guest_memfd inode: > > https://lore.kernel.org/all/cover.1691446946.git.ackerleytng@google.com > > > > There was a lot of discussion for this, but it's scattered all over the= place. > > The TL;DR is is that the inode will represent physical memory, and a fi= le will > > represent a given "struct kvm" instance's view of that memory. And so = the memory > > isn't reclaimed until the inode is truncated/punched. > > > > I _think_ this reflects the most recent plan from the guest_memfd side: > > https://lore.kernel.org/all/1233d749211c08d51f9ca5d427938d47f008af1f.16= 89893403.git.isaku.yamahata@intel.com Doh, sitting in my TODO folder... https://lore.kernel.org/all/20231016115028.996656-1-michael.roth@amd.com > Thanks for pointing that out. I think this might be the way to go. > I'll have a closer look at this and see how to get it to work with > pKVM. 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charset="utf-8" Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kvm@vger.kernel.org, David Hildenbrand , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Chao Peng , linux-riscv@lists.infradead.org, Isaku Yamahata , Marc Zyngier , Huacai Chen , Xiaoyao Li , "Matthew Wilcox \(Oracle\)" , Wang , Vlastimil Babka , Yu Zhang , Maciej Szmigiero , Albert Ou , Michael Roth , Ackerley Tng , Alexander Viro , Paul Walmsley , kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, =?utf-8?Q?Micka=C3=ABl_Sala=C3=BCn?= , Isaku Yamahata , Christian Brauner , Quentin Perret , Liam Merwick , linux-mips@vger.kernel.org, Oliver Upton , David Matlack , Jarkko Sakkinen , Palmer Dabbelt , "Kirill A . Shutemov" , kvm-riscv@lists.infradead.org, Anup Patel , linux-fsdevel@vger.kernel.org, Paolo Bonzini , Andrew Morton , Vishal Annapurve , linuxppc-dev@lists.ozlabs.org, Xu Yilun , Anish Moorthy Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Thu, Nov 02, 2023, Fuad Tabba wrote: > On Wed, Nov 1, 2023 at 9:55=E2=80=AFPM Sean Christopherson wrote: > > E.g. a misbehaving userspace could prematurely delete a memslot. And t= he more > > fun example is intrahost migration, where the plan is to allow pointing= multiple > > guest_memfd files at a single guest_memfd inode: > > https://lore.kernel.org/all/cover.1691446946.git.ackerleytng@google.com > > > > There was a lot of discussion for this, but it's scattered all over the= place. > > The TL;DR is is that the inode will represent physical memory, and a fi= le will > > represent a given "struct kvm" instance's view of that memory. And so = the memory > > isn't reclaimed until the inode is truncated/punched. > > > > I _think_ this reflects the most recent plan from the guest_memfd side: > > https://lore.kernel.org/all/1233d749211c08d51f9ca5d427938d47f008af1f.16= 89893403.git.isaku.yamahata@intel.com Doh, sitting in my TODO folder... https://lore.kernel.org/all/20231016115028.996656-1-michael.roth@amd.com > Thanks for pointing that out. I think this might be the way to go. > I'll have a closer look at this and see how to get it to work with > pKVM. 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Shutemov" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231103_161727_269521_F9FA13B7 X-CRM114-Status: GOOD ( 17.04 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org T24gVGh1LCBOb3YgMDIsIDIwMjMsIEZ1YWQgVGFiYmEgd3JvdGU6Cj4gT24gV2VkLCBOb3YgMSwg MjAyMyBhdCA5OjU14oCvUE0gU2VhbiBDaHJpc3RvcGhlcnNvbiA8c2VhbmpjQGdvb2dsZS5jb20+ IHdyb3RlOgo+ID4gRS5nLiBhIG1pc2JlaGF2aW5nIHVzZXJzcGFjZSBjb3VsZCBwcmVtYXR1cmVs eSBkZWxldGUgYSBtZW1zbG90LiAgQW5kIHRoZSBtb3JlCj4gPiBmdW4gZXhhbXBsZSBpcyBpbnRy YWhvc3QgbWlncmF0aW9uLCB3aGVyZSB0aGUgcGxhbiBpcyB0byBhbGxvdyBwb2ludGluZyBtdWx0 aXBsZQo+ID4gZ3Vlc3RfbWVtZmQgZmlsZXMgYXQgYSBzaW5nbGUgZ3Vlc3RfbWVtZmQgaW5vZGU6 Cj4gPiBodHRwczovL2xvcmUua2VybmVsLm9yZy9hbGwvY292ZXIuMTY5MTQ0Njk0Ni5naXQuYWNr ZXJsZXl0bmdAZ29vZ2xlLmNvbQo+ID4KPiA+IFRoZXJlIHdhcyBhIGxvdCBvZiBkaXNjdXNzaW9u IGZvciB0aGlzLCBidXQgaXQncyBzY2F0dGVyZWQgYWxsIG92ZXIgdGhlIHBsYWNlLgo+ID4gVGhl IFRMO0RSIGlzIGlzIHRoYXQgdGhlIGlub2RlIHdpbGwgcmVwcmVzZW50IHBoeXNpY2FsIG1lbW9y eSwgYW5kIGEgZmlsZSB3aWxsCj4gPiByZXByZXNlbnQgYSBnaXZlbiAic3RydWN0IGt2bSIgaW5z dGFuY2UncyB2aWV3IG9mIHRoYXQgbWVtb3J5LiAgQW5kIHNvIHRoZSBtZW1vcnkKPiA+IGlzbid0 IHJlY2xhaW1lZCB1bnRpbCB0aGUgaW5vZGUgaXMgdHJ1bmNhdGVkL3B1bmNoZWQuCj4gPgo+ID4g SSBfdGhpbmtfIHRoaXMgcmVmbGVjdHMgdGhlIG1vc3QgcmVjZW50IHBsYW4gZnJvbSB0aGUgZ3Vl c3RfbWVtZmQgc2lkZToKPiA+IGh0dHBzOi8vbG9yZS5rZXJuZWwub3JnL2FsbC8xMjMzZDc0OTIx MWMwOGQ1MWY5Y2E1ZDQyNzkzOGQ0N2YwMDhhZjFmLjE2ODk4OTM0MDMuZ2l0LmlzYWt1LnlhbWFo YXRhQGludGVsLmNvbQoKRG9oLCBzaXR0aW5nIGluIG15IFRPRE8gZm9sZGVyLi4uCgpodHRwczov L2xvcmUua2VybmVsLm9yZy9hbGwvMjAyMzEwMTYxMTUwMjguOTk2NjU2LTEtbWljaGFlbC5yb3Ro QGFtZC5jb20KCj4gVGhhbmtzIGZvciBwb2ludGluZyB0aGF0IG91dC4gSSB0aGluayB0aGlzIG1p Z2h0IGJlIHRoZSB3YXkgdG8gZ28uCj4gSSdsbCBoYXZlIGEgY2xvc2VyIGxvb2sgYXQgdGhpcyBh bmQgc2VlIGhvdyB0byBnZXQgaXQgdG8gd29yayB3aXRoCj4gcEtWTS4KCl9fX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fCmxpbnV4LWFybS1rZXJuZWwgbWFpbGlu ZyBsaXN0CmxpbnV4LWFybS1rZXJuZWxAbGlzdHMuaW5mcmFkZWFkLm9yZwpodHRwOi8vbGlzdHMu aW5mcmFkZWFkLm9yZy9tYWlsbWFuL2xpc3RpbmZvL2xpbnV4LWFybS1rZXJuZWwK