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AFNElJ+hGvM/OMnz6Ue6W/o5MfoIJBKQmtI06ydw5M6YGfJRvNSU9dtUUyHwo1+9PkymE6Lqxk8Ukvosig==@kvack.org X-Gm-Message-State: AOJu0Yz3NTuz3RSxsg6rN2Lcg+nD9e+irPqFkewOWuyLP/hNkN+KnDLC 2dJ1zpSgRv6+OMTR9gfvU5O2q6PesbN7nbGcBE8rQ9dDTqj45q4XBtBtxqAvs/Z9yj5dbRa6vax UHcRDaw== X-Received: from pgja21.prod.google.com ([2002:a63:cd55:0:b0:c82:7761:9936]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:a49:b0:3b3:bf95:f7e3 with SMTP id adf61e73a8af0-3bfed477967mr2785820637.43.1782924900819; Wed, 01 Jul 2026 09:55:00 -0700 (PDT) Date: Wed, 1 Jul 2026 09:55:00 -0700 In-Reply-To: <739e6834-40b3-405b-ada4-d31c38d8416a@intel.com> Mime-Version: 1.0 References: <20260618-gmem-inplace-conversion-v8-0-9d2959357853@google.com> <20260618-gmem-inplace-conversion-v8-6-9d2959357853@google.com> <739e6834-40b3-405b-ada4-d31c38d8416a@intel.com> Message-ID: Subject: Re: [PATCH v8 06/46] KVM: Enumerate support for PRIVATE memory iff kvm_arch_has_private_mem is defined From: Sean Christopherson To: Xiaoyao Li Cc: ackerleytng@google.com, aik@amd.com, andrew.jones@linux.dev, binbin.wu@linux.intel.com, brauner@kernel.org, chao.p.peng@linux.intel.com, david@kernel.org, jmattson@google.com, jthoughton@google.com, michael.roth@amd.com, oupton@kernel.org, pankaj.gupta@amd.com, qperret@google.com, rick.p.edgecombe@intel.com, rientjes@google.com, shivankg@amd.com, steven.price@arm.com, tabba@google.com, willy@infradead.org, wyihan@google.com, yan.y.zhao@intel.com, forkloop@google.com, pratyush@kernel.org, suzuki.poulose@arm.com, aneesh.kumar@kernel.org, liam@infradead.org, Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Jonathan Corbet , Shuah Khan , Shuah Khan , Vishal Annapurve , Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Youngjun Park , Qi Zheng , Shakeel Butt , Kiryl Shutsemau , Baoquan He , Jason Gunthorpe , Vlastimil Babka , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev Content-Type: text/plain; charset="us-ascii" X-Stat-Signature: r7o93omqur1whrjh19j5cudidpaerzq4 X-Rspamd-Queue-Id: 4FD7C160006 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1782924902-645111 X-HE-Meta: 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 /CIqkArN 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Jul 01, 2026, Xiaoyao Li wrote: > On 6/19/2026 8:31 AM, Ackerley Tng via B4 Relay wrote: > > From: Ackerley Tng > > > > Explicitly guard reporting support for KVM_MEMORY_ATTRIBUTE_PRIVATE based > > on kvm_arch_has_private_mem being #defined in anticipation of decoupling > > kvm_supported_mem_attributes() from CONFIG_KVM_VM_MEMORY_ATTRIBUTES. > > Well, after this series, kvm_supported_mem_attributes() is renamed to > kvm_supported_vm_mem_attributes(), and it's still under > CONFIG_KVM_VM_MEMORY_ATTRIBUTES. > > > guest_memfd support for memory attributes will be unconditional to avoid > > yet more macros (all architectures that support guest_memfd are expected to > > use per-gmem attributes at some point), at which point enumerating support > > KVM_MEMORY_ATTRIBUTE_PRIVATE based solely on memory attributes being > > supported _somewhere_ would result in KVM over-reporting support on arm64. > > I don't understand it. This patch only changes the behavior of > kvm_supported_mem_attributes(), the usage of which is guarded by > CONFIG_KVM_VM_MEMORY_ATTRIBUTESq. This is config is only visible to x86 due > to patch 03. How does it affect arm64? Hrm, yeah, this is messed up. Ahh, I think Ackerley shuffled things around and "broke" stuff in the process. In v7[1] and earlier, the diff was this: diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 091f201251159..68142bc962953 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -722,7 +722,7 @@ static inline int kvm_arch_vcpu_memslots_id(struct kvm_vcpu *vcpu) } #endif -#ifndef CONFIG_KVM_VM_MEMORY_ATTRIBUTES +#ifndef kvm_arch_has_private_mem static inline bool kvm_arch_has_private_mem(struct kvm *kvm) { return false; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 306153abbafa5..abb9cfa3eb04d 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2421,8 +2421,10 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm, #ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES static u64 kvm_supported_mem_attributes(struct kvm *kvm) { +#ifdef kvm_arch_has_private_mem if (!kvm || kvm_arch_has_private_mem(kvm)) return KVM_MEMORY_ATTRIBUTE_PRIVATE; +#endif return 0; } which makes a *lot* more sense given the changelog (and IMO for the ordering in general). In v8 here, Ackerley combined part of a change[2] (that I provided off-list) with part of this commit, to create patch 4, "KVM: Decouple kvm_has_arch_private_mem from CONFIG_KVM_VM_MEMORY_ATTRIBUTESthe". Ackerley, the cover letter says: + Reshuffled the earlier commits that deal with preparing KVM to stop seeing VM memory attributes as the only source of attributes. but there's no explanation for *why* the reshuffling was done. Reorganizing code like this at v8 of a series this size is a big "no-no" unless there's a *really* good reason to do so. In addition to the resulting confusion, changes like this invalidate Fuad's Reviewed-by. And since it's obviously quite difficult to tease out exactly what changed, it's not realistic to re-review things without doing a deep audit of the series, which no one wants to do for a series that is/was so close to being fully ready. And without such an audit, I can't accept the patches, because I can't trust that what I am accepting is what I and others have reviewed. So, except where there is/was a *need* to shuffle things around relative to v7, I think we should revert back to the v7 ordering for v9. And where there is a need to rework things, each and every one of those needs to be explicitly documented, because "Reshuffled the earlier commits" is grossly insufficient. [1] https://lore.kernel.org/all/20260522-gmem-inplace-conversion-v7-3-2f0fae496530@google.com [2] https://github.com/sean-jc/linux/commit/8a475b1bcf89f1cf776ed9ce7d6bb587aab0d421