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AHgh+RqyRnUzwWgAFFoWJb4LyL94YQKeqoMi/bWWrmfTW6o9THzkmmQnPQaZ8Ku31cc+YhWzoaFk+7ep0Sf3JASS8EaAKXs=@vger.kernel.org X-Gm-Message-State: AOJu0Yy9DDyB8swDKsTjegCZhwcs6I1r4awj4tLYV30l4iAkI4+Q+wkG fopzvoceFK/Hta3hNJEqq2h6LhwntBgLfVC69uFNTuhBXH5QlRcsB1U7JrvURnM+NF9ITVUFn4m z+wEcJg== X-Received: from pgip24.prod.google.com ([2002:a63:c158:0:b0:c82:7761:9936]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:a103:b0:3bf:6237:4d3f with SMTP id adf61e73a8af0-3cb85e4dc7fmr1611110637.18.1785878762819; Tue, 04 Aug 2026 14:26:02 -0700 (PDT) Date: Tue, 4 Aug 2026 14:26:02 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260728-gmem-inplace-conversion-v9-0-35f9aec2aed2@google.com> <20260728-gmem-inplace-conversion-v9-20-35f9aec2aed2@google.com> <7f23d149-b7f0-465a-a9c0-5c7484e289d2@intel.com> Message-ID: Subject: Re: [PATCH v9 20/41] KVM: Let userspace disable per-VM mem attributes, enable per-gmem attributes From: Sean Christopherson To: Ackerley Tng Cc: Xiaoyao Li , 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 , John Hubbard , Peter Xu , 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" On Tue, Aug 04, 2026, Ackerley Tng wrote: > Xiaoyao Li writes: > > > > > [...snip...] > > > >> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > >> index ea2752989f8bd..df67a6188aa99 100644 > >> --- a/virt/kvm/guest_memfd.c > >> +++ b/virt/kvm/guest_memfd.c > >> @@ -1137,10 +1137,12 @@ static bool kvm_range_is_private(struct file *file, pgoff_t index, > >> { > >> struct inode *inode = file_inode(file); > >> > >> +#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES > >> if (!gmem_in_place_conversion) > >> return kvm_range_has_vm_memory_attributes(kvm, gfn, gfn + nr_pages, > >> KVM_MEMORY_ATTRIBUTE_PRIVATE, > >> KVM_MEMORY_ATTRIBUTE_PRIVATE); > >> +#endif > >> > >> return kvm_gmem_range_has_attributes(inode, index, nr_pages, > >> KVM_MEMORY_ATTRIBUTE_PRIVATE); > > > > With my suggestion[1] on patch 7, this diff block can be dropped. > > > > [1] > > https://lore.kernel.org/all/dd4201f2-3660-46ad-958f-c70feb1ab1c3@intel.com/ > > > > The code looks good to me, > > > > Reviewed-by: Xiaoyao Li > > > > I think your earlier suggestion on only defining the module_param when > CONFIG_KVM_VM_MEMORY_ATTRIBUTES is selected still applies, since it > removes an avenue for a user to turn off gmem_in_place_conversion if > the other option (VM memory attributes) isn't available. > > +#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES > +module_param(gmem_in_place_conversion, bool, 0444); > +#endif > > Given that we're now dropping the diff block as you suggested, do you > agree that we should keep this #ifdef? Yes, the param needs to remain hidden if CONFIG_KVM_VM_MEMORY_ATTRIBUTES=n, so that userspace attempts to disable gmem_in_place_conversion are ignored (and logged as such). The obvious downside is that the param won't exist when in-place conversion is forced on, which is kinda weird, but I think it's the lesser evil?