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bh=OBC8s70Cm9Vl9909TPa9He89N57kiPFL/8T7CN2yHJY=; b=HY1cZsxHtfEW0DZfoXB8ozOVA7ZaPzNZpG+AXu/dBWNid3SuJY+rAZcVQbzpAxGcvxPc7L GydItYtvLbiZsuCA== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 610F43EA63; Tue, 16 Dec 2025 14:02:03 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 7L7+B1tmQWleMgAAD6G6ig (envelope-from ); Tue, 16 Dec 2025 14:02:03 +0000 From: Fabiano Rosas To: Peter Xu , qemu-devel@nongnu.org Cc: Juraj Marcin , David Hildenbrand , Paolo Bonzini , Chenyi Qiang , peterx@redhat.com, Alexey Kardashevskiy , Li Xiaoyao Subject: Re: [PATCH v3 08/12] hostmem: Support fully shared guest memfd to back a VM In-Reply-To: <20251215205203.1185099-9-peterx@redhat.com> References: <20251215205203.1185099-1-peterx@redhat.com> <20251215205203.1185099-9-peterx@redhat.com> Date: Tue, 16 Dec 2025 11:02:00 -0300 Message-ID: <87tsxq1q5j.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain X-Spamd-Result: default: False [-4.51 / 50.00]; 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envelope-from=farosas@suse.de; helo=smtp-out1.suse.de X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Peter Xu writes: > Host backends supports guest-memfd now by detecting whether it's a > confidential VM. There's no way to choose it yet from the memory level to > use it fully shared. If we use guest-memfd, it so far always implies we > need two layers of memory backends, while the guest-memfd only provides the > private set of pages. > > This patch introduces a way so that QEMU can consume guest memfd as the > only source of memory to back the object (aka, fully shared). > > To use the fully shared guest-memfd, one can add a memfd object with: > > -object memory-backend-memfd,guest-memfd=on,share=on > > Note that share=on is required with fully shared guest_memfd. > > PS: there's a trivial touch-up on fd<0 check, because the stub to create > guest-memfd may return negative but not -1. > > Signed-off-by: Peter Xu Reviewed-by: Fabiano Rosas