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X-CSE-ConnectionGUID: HXI2P0nKTceGhEkSSjAtBA== X-CSE-MsgGUID: VnhrjQVtTW6CDoTjMvcsNA== X-IronPort-AV: E=McAfee;i="6800,10657,11495"; a="54313059" X-IronPort-AV: E=Sophos;i="6.16,320,1744095600"; d="scan'208";a="54313059" Received: from orviesa003.jf.intel.com ([10.64.159.143]) by fmvoesa112.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Jul 2025 20:33:26 -0700 X-CSE-ConnectionGUID: /scvanS6Sx+UV2IV+v5vuQ== X-CSE-MsgGUID: JlCfL47DR5aRJITyOXDjvg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.16,320,1744095600"; d="scan'208";a="162232198" Received: from xiaoyaol-hp-g830.ccr.corp.intel.com (HELO [10.124.247.1]) ([10.124.247.1]) by ORVIESA003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Jul 2025 20:33:12 -0700 Message-ID: Date: Fri, 18 Jul 2025 11:33:08 +0800 Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v15 09/21] KVM: guest_memfd: Track guest_memfd mmap support in memslot To: Fuad Tabba , kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, kvmarm@lists.linux.dev Cc: pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, seanjc@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@google.com, mail@maciej.szmigiero.name, david@redhat.com, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, jthoughton@google.com, peterx@redhat.com, pankaj.gupta@amd.com, ira.weiny@intel.com References: <20250717162731.446579-1-tabba@google.com> <20250717162731.446579-10-tabba@google.com> Content-Language: en-US From: Xiaoyao Li In-Reply-To: <20250717162731.446579-10-tabba@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 7/18/2025 12:27 AM, Fuad Tabba wrote: > Add a new internal flag, KVM_MEMSLOT_GMEM_ONLY, to the top half of > memslot->flags (which makes it strictly for KVM's internal use). This > flag tracks when a guest_memfd-backed memory slot supports host > userspace mmap operations, which implies that all memory, not just > private memory for CoCo VMs, is consumed through guest_memfd: "gmem > only". > > This optimization avoids repeatedly checking the underlying guest_memfd > file for mmap support, which would otherwise require taking and > releasing a reference on the file for each check. By caching this > information directly in the memslot, we reduce overhead and simplify the > logic involved in handling guest_memfd-backed pages for host mappings. > > Reviewed-by: Gavin Shan > Reviewed-by: Shivank Garg > Acked-by: David Hildenbrand > Suggested-by: David Hildenbrand > Signed-off-by: Fuad Tabba Reviewed-by: Xiaoyao Li