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Tue, 09 Jul 2024 14:13:28 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHjKrk0zZyquX0++cfLkFxfG6jz6dn5RLDqhkSPdbZSMNWq4ssGoVBep4JrbyTepRRnJeOnww== X-Received: by 2002:a05:6a20:c22:b0:1be:c88f:c60d with SMTP id adf61e73a8af0-1c2984d82d1mr2721153637.56.1720559608048; Tue, 09 Jul 2024 14:13:28 -0700 (PDT) Received: from [172.31.79.51] ([216.9.110.4]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fbb6a12fe4sm20538215ad.56.2024.07.09.14.13.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Jul 2024 14:13:27 -0700 (PDT) Message-ID: <47ce1b10-e031-4ac1-b88f-9d4194533745@redhat.com> Date: Tue, 9 Jul 2024 23:13:25 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 8/8] kvm: gmem: Allow restricted userspace mappings To: Fuad Tabba , Patrick Roy Cc: seanjc@google.com, pbonzini@redhat.com, akpm@linux-foundation.org, dwmw@amazon.co.uk, rppt@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, willy@infradead.org, graf@amazon.com, derekmn@amazon.com, kalyazin@amazon.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, dmatlack@google.com, chao.p.peng@linux.intel.com, xmarcalx@amazon.co.uk References: <20240709132041.3625501-1-roypat@amazon.co.uk> <20240709132041.3625501-9-roypat@amazon.co.uk> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: C5BFBA0019 X-Stat-Signature: ku93ptcia9ddk3y36jn8zj1cfnj3ye16 X-Rspam-User: X-HE-Tag: 1720559611-237796 X-HE-Meta: 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 ycaR7gJo Wj83S26LNIk2p/FdOi6Be8+q34uHAXa938vgaWw6xvWBJ95kOkQxteRJ9UHpBElU05eJ4i/XF2DB9nhpbpzdEzSpTRnIYL6EPpmRxiG+CRIvzoylJr5VWtD71RUA8NUJxWuevQ2kM29gSRMi6jVH8GaKh+SnhAu6ry7a3m0oBBGOm/Y0tXVjPsfizviNkvy9KixtMSkI+PFYK4fNqflbNHCD/cS9lPGumgIqfwpdHnDT6aVRlOQcbkgjDddSB2krwnbSzSaZivjWsZWEC4Li4KEM7OjU/zb2lHEN1sOCbbFUx4YxlvhLqBCuOZwz2rssQyew10lfq7/wdN9iRjj2JV7BCKtSPeQt68Rwubo8H9upYejbcdkH3cHNceZ6FKbsmWPlLypAmwVyKuA8KIH6zjE+cDfPUMTApFT9EjB+97OO1KPUbahdpPZKEjQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 09.07.24 16:48, Fuad Tabba wrote: > Hi Patrick, > > On Tue, Jul 9, 2024 at 2:21 PM Patrick Roy wrote: >> >> Allow mapping guest_memfd into userspace. Since AS_INACCESSIBLE is set >> on the underlying address_space struct, no GUP of guest_memfd will be >> possible. > > This patch allows mapping guest_memfd() unconditionally. Even if it's > not guppable, there are other reasons why you wouldn't want to allow > this. Maybe a config flag to gate it? e.g., As discussed with Jason, maybe not the direction we want to take with guest_memfd. If it's private memory, it shall not be mapped. Also not via magic config options. We'll likely discuss some of that in the meeting MM tomorrow I guess (having both shared and private memory in guest_memfd). Note that just from staring at this commit, I don't understand the motivation *why* we would want to do that. -- Cheers, David / dhildenb