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X-CSE-ConnectionGUID: 5nN7bScuTBi5rml/x0bB2Q== X-CSE-MsgGUID: qDwl7TTjTOOvZlozcYfcGw== X-IronPort-AV: E=McAfee;i="6800,10657,11833"; a="94789729" X-IronPort-AV: E=Sophos;i="6.25,141,1779174000"; d="scan'208";a="94789729" Received: from orviesa004.jf.intel.com ([10.64.159.144]) by orvoesa105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Jul 2026 04:18:50 -0700 X-CSE-ConnectionGUID: aLlyHiwUTXyhs4lgY+f9QQ== X-CSE-MsgGUID: bSTU4KQCQOiPSgzMr577Lw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,141,1779174000"; d="scan'208";a="256461895" Received: from unknown (HELO [10.239.158.49]) ([10.239.158.49]) by orviesa004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Jul 2026 04:18:31 -0700 Message-ID: Date: Wed, 1 Jul 2026 19:18:27 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 25/46] KVM: guest_memfd: Enable INIT_SHARED on guest_memfd for x86 Coco VMs To: 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 , Sean Christopherson , 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 Cc: 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 References: <20260618-gmem-inplace-conversion-v8-0-9d2959357853@google.com> <20260618-gmem-inplace-conversion-v8-25-9d2959357853@google.com> Content-Language: en-US From: Xiaoyao Li In-Reply-To: <20260618-gmem-inplace-conversion-v8-25-9d2959357853@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 1ACEA18000A X-Stat-Signature: 3zg9gta68amt6qp58j594fxocipeirky X-HE-Tag: 1782904731-569930 X-HE-Meta: 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 BLCtvFat KM9lcdMJhR19RVFZelLxu/71Hiin9mZNih05yGPt2CNfc3mVCriA1wGGYym9FnQqMlOaPsYplsATDYUSmPefBdn3R5U1l26QBkVJjqYHgnJpgCCBnlvUfOjouifqlaxxgurX3NAGtX74F0HCrM/bkWofeq+tVmAppqIBH+eX/+J7xWpVHaQ38TJktpiYUASPx6IEionrxRwQtr4ZfvCfmCCCPUbKV05bXxxg4hcCaSqZoBD9yA8uL7ktAKqriLywpd+UepPZ5q2OJ8Z/jGP8DkKAcR486Rck7Bv0SYx/yBJzJzvcdLoRHH7d1h8ckNoTm8rBUlTZZdVnNMjT4OsTEo4+Hig== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/19/2026 8:32 AM, Ackerley Tng via B4 Relay wrote: > From: Sean Christopherson > > Now that guest_memfd supports tracking private vs. shared within gmem > itself, allow userspace to specify INIT_SHARED on a guest_memfd instance > for x86 Confidential Computing (CoCo) VMs, so long as in-place conversion > is enabled, i.e. when it's actually possible for a guest_memfd instance to > contain shared memory. > > Signed-off-by: Sean Christopherson > Reviewed-by: Fuad Tabba > Signed-off-by: Ackerley Tng Reviewed-by: Xiaoyao Li > --- > arch/x86/kvm/x86.c | 13 +++++++------ > 1 file changed, 7 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 2fde594e86d72..57a543dadb851 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -14116,14 +14116,15 @@ bool kvm_arch_no_poll(struct kvm_vcpu *vcpu) > } > > #ifdef CONFIG_KVM_GUEST_MEMFD > -/* > - * KVM doesn't yet support initializing guest_memfd memory as shared for VMs > - * with private memory (the private vs. shared tracking needs to be moved into > - * guest_memfd). > - */ > bool kvm_arch_supports_gmem_init_shared(struct kvm *kvm) > { > - return !kvm_arch_has_private_mem(kvm); > + /* > + * INIT_SHARED is supported if in-place conversion is enabled, or if > + * the VM doesn't support private memory. If the VM has private memory > + * and in-place conversion is disabled, then guest_memfd can _only_ be > + * used for private memory. > + */ > + return gmem_in_place_conversion || !kvm_arch_has_private_mem(kvm); > } > > #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_PREPARE >