From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sean Christopherson Date: Wed, 1 Nov 2023 15:34:58 -0700 Subject: [PATCH v13 17/35] KVM: Add transparent hugepage support for dedicated guest memory In-Reply-To: <4ca2253d-276f-43c5-8e9f-0ded5d5b2779@redhat.com> References: <20231027182217.3615211-1-seanjc@google.com> <20231027182217.3615211-18-seanjc@google.com> <7c0844d8-6f97-4904-a140-abeabeb552c1@intel.com> <92ba7ddd-2bc8-4a8d-bd67-d6614b21914f@intel.com> <4ca2253d-276f-43c5-8e9f-0ded5d5b2779@redhat.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 Wed, Nov 01, 2023, Paolo Bonzini wrote: > On 11/1/23 17:36, Sean Christopherson wrote: > > > > "Allow" isn't perfect, e.g. I would much prefer a straight KVM_GUEST_MEMFD_USE_HUGEPAGES > > > > or KVM_GUEST_MEMFD_HUGEPAGES flag, but I wanted the name to convey that KVM doesn't > > > > (yet) guarantee hugepages. I.e. KVM_GUEST_MEMFD_ALLOW_HUGEPAGE is stronger than > > > > a hint, but weaker than a requirement. And if/when KVM supports a dedicated memory > > > > pool of some kind, then we can add KVM_GUEST_MEMFD_REQUIRE_HUGEPAGE. > > > I think that the current patch is fine, but I will adjust it to always > > > allow the flag, and to make the size check even if !CONFIG_TRANSPARENT_HUGEPAGE. > > > If hugepages are not guaranteed, and (theoretically) you could have no > > > hugepage at all in the result, it's okay to get this result even if THP is not > > > available in the kernel. > > Can you post a fixup patch? It's not clear to me exactly what behavior you intend > > to end up with. > > Sure, just this: > > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > index 7d1a33c2ad42..34fd070e03d9 100644 > --- a/virt/kvm/guest_memfd.c > +++ b/virt/kvm/guest_memfd.c > @@ -430,10 +430,7 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) > { > loff_t size = args->size; > u64 flags = args->flags; > - u64 valid_flags = 0; > - > - if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) > - valid_flags |= KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; > + u64 valid_flags = KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; > if (flags & ~valid_flags) > return -EINVAL; > @@ -441,11 +438,9 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) > if (size < 0 || !PAGE_ALIGNED(size)) > return -EINVAL; > -#ifdef CONFIG_TRANSPARENT_HUGEPAGE > if ((flags & KVM_GUEST_MEMFD_ALLOW_HUGEPAGE) && > !IS_ALIGNED(size, HPAGE_PMD_SIZE)) > return -EINVAL; > -#endif That won't work, HPAGE_PMD_SIZE is valid only for CONFIG_TRANSPARENT_HUGEPAGE=y. #else /* CONFIG_TRANSPARENT_HUGEPAGE */ #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; }) #define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; }) #define HPAGE_PMD_SIZE ({ BUILD_BUG(); 0; }) ... > return __kvm_gmem_create(kvm, size, flags); > } > > Paolo > From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (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 AF0B953B1 for ; Wed, 1 Nov 2023 22:35:00 +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="xwve43fp" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-5aecf6e30e9so5641947b3.1 for ; Wed, 01 Nov 2023 15:35:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; 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Wed, 01 Nov 2023 15:34:59 -0700 (PDT) Date: Wed, 1 Nov 2023 15:34:58 -0700 In-Reply-To: <4ca2253d-276f-43c5-8e9f-0ded5d5b2779@redhat.com> 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> <20231027182217.3615211-18-seanjc@google.com> <7c0844d8-6f97-4904-a140-abeabeb552c1@intel.com> <92ba7ddd-2bc8-4a8d-bd67-d6614b21914f@intel.com> <4ca2253d-276f-43c5-8e9f-0ded5d5b2779@redhat.com> Message-ID: Subject: Re: [PATCH v13 17/35] KVM: Add transparent hugepage support for dedicated guest memory From: Sean Christopherson To: Paolo Bonzini Cc: Xiaoyao Li , 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, Xu Yilun , Chao Peng , Fuad Tabba , 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="us-ascii" On Wed, Nov 01, 2023, Paolo Bonzini wrote: > On 11/1/23 17:36, Sean Christopherson wrote: > > > > "Allow" isn't perfect, e.g. I would much prefer a straight KVM_GUEST_MEMFD_USE_HUGEPAGES > > > > or KVM_GUEST_MEMFD_HUGEPAGES flag, but I wanted the name to convey that KVM doesn't > > > > (yet) guarantee hugepages. I.e. KVM_GUEST_MEMFD_ALLOW_HUGEPAGE is stronger than > > > > a hint, but weaker than a requirement. And if/when KVM supports a dedicated memory > > > > pool of some kind, then we can add KVM_GUEST_MEMFD_REQUIRE_HUGEPAGE. > > > I think that the current patch is fine, but I will adjust it to always > > > allow the flag, and to make the size check even if !CONFIG_TRANSPARENT_HUGEPAGE. > > > If hugepages are not guaranteed, and (theoretically) you could have no > > > hugepage at all in the result, it's okay to get this result even if THP is not > > > available in the kernel. > > Can you post a fixup patch? It's not clear to me exactly what behavior you intend > > to end up with. > > Sure, just this: > > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > index 7d1a33c2ad42..34fd070e03d9 100644 > --- a/virt/kvm/guest_memfd.c > +++ b/virt/kvm/guest_memfd.c > @@ -430,10 +430,7 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) > { > loff_t size = args->size; > u64 flags = args->flags; > - u64 valid_flags = 0; > - > - if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) > - valid_flags |= KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; > + u64 valid_flags = KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; > if (flags & ~valid_flags) > return -EINVAL; > @@ -441,11 +438,9 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) > if (size < 0 || !PAGE_ALIGNED(size)) > return -EINVAL; > -#ifdef CONFIG_TRANSPARENT_HUGEPAGE > if ((flags & KVM_GUEST_MEMFD_ALLOW_HUGEPAGE) && > !IS_ALIGNED(size, HPAGE_PMD_SIZE)) > return -EINVAL; > -#endif That won't work, HPAGE_PMD_SIZE is valid only for CONFIG_TRANSPARENT_HUGEPAGE=y. #else /* CONFIG_TRANSPARENT_HUGEPAGE */ #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; }) #define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; }) #define HPAGE_PMD_SIZE ({ BUILD_BUG(); 0; }) ... > return __kvm_gmem_create(kvm, size, flags); > } > > Paolo > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DF171C4332F for ; Wed, 1 Nov 2023 22:35:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:From:Subject:Message-ID: References:Mime-Version:In-Reply-To:Date:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; 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Wed, 01 Nov 2023 15:34:59 -0700 (PDT) Date: Wed, 1 Nov 2023 15:34:58 -0700 In-Reply-To: <4ca2253d-276f-43c5-8e9f-0ded5d5b2779@redhat.com> Mime-Version: 1.0 References: <20231027182217.3615211-1-seanjc@google.com> <20231027182217.3615211-18-seanjc@google.com> <7c0844d8-6f97-4904-a140-abeabeb552c1@intel.com> <92ba7ddd-2bc8-4a8d-bd67-d6614b21914f@intel.com> <4ca2253d-276f-43c5-8e9f-0ded5d5b2779@redhat.com> Message-ID: Subject: Re: [PATCH v13 17/35] KVM: Add transparent hugepage support for dedicated guest memory From: Sean Christopherson To: Paolo Bonzini Cc: Xiaoyao Li , 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, Xu Yilun , Chao Peng , Fuad Tabba , 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" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231101_153502_037695_410A50A8 X-CRM114-Status: GOOD ( 26.54 ) X-BeenThere: linux-riscv@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="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Wed, Nov 01, 2023, Paolo Bonzini wrote: > On 11/1/23 17:36, Sean Christopherson wrote: > > > > "Allow" isn't perfect, e.g. I would much prefer a straight KVM_GUEST_MEMFD_USE_HUGEPAGES > > > > or KVM_GUEST_MEMFD_HUGEPAGES flag, but I wanted the name to convey that KVM doesn't > > > > (yet) guarantee hugepages. I.e. KVM_GUEST_MEMFD_ALLOW_HUGEPAGE is stronger than > > > > a hint, but weaker than a requirement. And if/when KVM supports a dedicated memory > > > > pool of some kind, then we can add KVM_GUEST_MEMFD_REQUIRE_HUGEPAGE. > > > I think that the current patch is fine, but I will adjust it to always > > > allow the flag, and to make the size check even if !CONFIG_TRANSPARENT_HUGEPAGE. > > > If hugepages are not guaranteed, and (theoretically) you could have no > > > hugepage at all in the result, it's okay to get this result even if THP is not > > > available in the kernel. > > Can you post a fixup patch? It's not clear to me exactly what behavior you intend > > to end up with. > > Sure, just this: > > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > index 7d1a33c2ad42..34fd070e03d9 100644 > --- a/virt/kvm/guest_memfd.c > +++ b/virt/kvm/guest_memfd.c > @@ -430,10 +430,7 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) > { > loff_t size = args->size; > u64 flags = args->flags; > - u64 valid_flags = 0; > - > - if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) > - valid_flags |= KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; > + u64 valid_flags = KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; > if (flags & ~valid_flags) > return -EINVAL; > @@ -441,11 +438,9 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) > if (size < 0 || !PAGE_ALIGNED(size)) > return -EINVAL; > -#ifdef CONFIG_TRANSPARENT_HUGEPAGE > if ((flags & KVM_GUEST_MEMFD_ALLOW_HUGEPAGE) && > !IS_ALIGNED(size, HPAGE_PMD_SIZE)) > return -EINVAL; > -#endif That won't work, HPAGE_PMD_SIZE is valid only for CONFIG_TRANSPARENT_HUGEPAGE=y. #else /* CONFIG_TRANSPARENT_HUGEPAGE */ #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; }) #define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; }) #define HPAGE_PMD_SIZE ({ BUILD_BUG(); 0; }) ... > return __kvm_gmem_create(kvm, size, flags); > } > > Paolo > _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 362E7C4332F for ; Wed, 1 Nov 2023 22:35:54 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20230601 header.b=nO+oAXc4; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4SLMKh2ThFz3cjr for ; 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Wed, 01 Nov 2023 15:34:59 -0700 (PDT) Date: Wed, 1 Nov 2023 15:34:58 -0700 In-Reply-To: <4ca2253d-276f-43c5-8e9f-0ded5d5b2779@redhat.com> Mime-Version: 1.0 References: <20231027182217.3615211-1-seanjc@google.com> <20231027182217.3615211-18-seanjc@google.com> <7c0844d8-6f97-4904-a140-abeabeb552c1@intel.com> <92ba7ddd-2bc8-4a8d-bd67-d6614b21914f@intel.com> <4ca2253d-276f-43c5-8e9f-0ded5d5b2779@redhat.com> Message-ID: Subject: Re: [PATCH v13 17/35] KVM: Add transparent hugepage support for dedicated guest memory From: Sean Christopherson To: Paolo Bonzini Content-Type: text/plain; charset="us-ascii" 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 , Fuad Tabba , Yu Zhang , Maciej Szmigiero , Albert Ou , Vlastimil Babka , 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 , A nup Patel , linux-mips@vger.kernel.org, Oliver Upton , David Matlack , Jarkko Sakkinen , Palmer Dabbelt , "Kirill A . Shutemov" , kvm-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, Liam Merwick , 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 Wed, Nov 01, 2023, Paolo Bonzini wrote: > On 11/1/23 17:36, Sean Christopherson wrote: > > > > "Allow" isn't perfect, e.g. I would much prefer a straight KVM_GUEST_MEMFD_USE_HUGEPAGES > > > > or KVM_GUEST_MEMFD_HUGEPAGES flag, but I wanted the name to convey that KVM doesn't > > > > (yet) guarantee hugepages. I.e. KVM_GUEST_MEMFD_ALLOW_HUGEPAGE is stronger than > > > > a hint, but weaker than a requirement. And if/when KVM supports a dedicated memory > > > > pool of some kind, then we can add KVM_GUEST_MEMFD_REQUIRE_HUGEPAGE. > > > I think that the current patch is fine, but I will adjust it to always > > > allow the flag, and to make the size check even if !CONFIG_TRANSPARENT_HUGEPAGE. > > > If hugepages are not guaranteed, and (theoretically) you could have no > > > hugepage at all in the result, it's okay to get this result even if THP is not > > > available in the kernel. > > Can you post a fixup patch? It's not clear to me exactly what behavior you intend > > to end up with. > > Sure, just this: > > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > index 7d1a33c2ad42..34fd070e03d9 100644 > --- a/virt/kvm/guest_memfd.c > +++ b/virt/kvm/guest_memfd.c > @@ -430,10 +430,7 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) > { > loff_t size = args->size; > u64 flags = args->flags; > - u64 valid_flags = 0; > - > - if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) > - valid_flags |= KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; > + u64 valid_flags = KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; > if (flags & ~valid_flags) > return -EINVAL; > @@ -441,11 +438,9 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) > if (size < 0 || !PAGE_ALIGNED(size)) > return -EINVAL; > -#ifdef CONFIG_TRANSPARENT_HUGEPAGE > if ((flags & KVM_GUEST_MEMFD_ALLOW_HUGEPAGE) && > !IS_ALIGNED(size, HPAGE_PMD_SIZE)) > return -EINVAL; > -#endif That won't work, HPAGE_PMD_SIZE is valid only for CONFIG_TRANSPARENT_HUGEPAGE=y. #else /* CONFIG_TRANSPARENT_HUGEPAGE */ #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; }) #define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; }) #define HPAGE_PMD_SIZE ({ BUILD_BUG(); 0; }) ... > return __kvm_gmem_create(kvm, size, flags); > } > > Paolo > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1F00DC4332F for ; Wed, 1 Nov 2023 22:35:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:From:Subject:Message-ID: References:Mime-Version:In-Reply-To:Date:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; 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Wed, 01 Nov 2023 15:34:59 -0700 (PDT) Date: Wed, 1 Nov 2023 15:34:58 -0700 In-Reply-To: <4ca2253d-276f-43c5-8e9f-0ded5d5b2779@redhat.com> Mime-Version: 1.0 References: <20231027182217.3615211-1-seanjc@google.com> <20231027182217.3615211-18-seanjc@google.com> <7c0844d8-6f97-4904-a140-abeabeb552c1@intel.com> <92ba7ddd-2bc8-4a8d-bd67-d6614b21914f@intel.com> <4ca2253d-276f-43c5-8e9f-0ded5d5b2779@redhat.com> Message-ID: Subject: Re: [PATCH v13 17/35] KVM: Add transparent hugepage support for dedicated guest memory From: Sean Christopherson To: Paolo Bonzini Cc: Xiaoyao Li , 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, Xu Yilun , Chao Peng , Fuad Tabba , 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" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231101_153502_376792_1252FF86 X-CRM114-Status: GOOD ( 28.17 ) 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="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Nov 01, 2023, Paolo Bonzini wrote: > On 11/1/23 17:36, Sean Christopherson wrote: > > > > "Allow" isn't perfect, e.g. I would much prefer a straight KVM_GUEST_MEMFD_USE_HUGEPAGES > > > > or KVM_GUEST_MEMFD_HUGEPAGES flag, but I wanted the name to convey that KVM doesn't > > > > (yet) guarantee hugepages. I.e. KVM_GUEST_MEMFD_ALLOW_HUGEPAGE is stronger than > > > > a hint, but weaker than a requirement. And if/when KVM supports a dedicated memory > > > > pool of some kind, then we can add KVM_GUEST_MEMFD_REQUIRE_HUGEPAGE. > > > I think that the current patch is fine, but I will adjust it to always > > > allow the flag, and to make the size check even if !CONFIG_TRANSPARENT_HUGEPAGE. > > > If hugepages are not guaranteed, and (theoretically) you could have no > > > hugepage at all in the result, it's okay to get this result even if THP is not > > > available in the kernel. > > Can you post a fixup patch? It's not clear to me exactly what behavior you intend > > to end up with. > > Sure, just this: > > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > index 7d1a33c2ad42..34fd070e03d9 100644 > --- a/virt/kvm/guest_memfd.c > +++ b/virt/kvm/guest_memfd.c > @@ -430,10 +430,7 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) > { > loff_t size = args->size; > u64 flags = args->flags; > - u64 valid_flags = 0; > - > - if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) > - valid_flags |= KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; > + u64 valid_flags = KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; > if (flags & ~valid_flags) > return -EINVAL; > @@ -441,11 +438,9 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) > if (size < 0 || !PAGE_ALIGNED(size)) > return -EINVAL; > -#ifdef CONFIG_TRANSPARENT_HUGEPAGE > if ((flags & KVM_GUEST_MEMFD_ALLOW_HUGEPAGE) && > !IS_ALIGNED(size, HPAGE_PMD_SIZE)) > return -EINVAL; > -#endif That won't work, HPAGE_PMD_SIZE is valid only for CONFIG_TRANSPARENT_HUGEPAGE=y. #else /* CONFIG_TRANSPARENT_HUGEPAGE */ #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; }) #define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; }) #define HPAGE_PMD_SIZE ({ BUILD_BUG(); 0; }) ... > return __kvm_gmem_create(kvm, size, flags); > } > > Paolo > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel