From: Fabiano Rosas <farosas@suse.de>
To: Peter Xu <peterx@redhat.com>, qemu-devel@nongnu.org
Cc: Juraj Marcin <jmarcin@redhat.com>,
David Hildenbrand <david@kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Chenyi Qiang <chenyi.qiang@intel.com>,
peterx@redhat.com, Alexey Kardashevskiy <aik@amd.com>,
Li Xiaoyao <xiaoyao.li@intel.com>
Subject: Re: [PATCH v3 08/12] hostmem: Support fully shared guest memfd to back a VM
Date: Tue, 16 Dec 2025 11:02:00 -0300 [thread overview]
Message-ID: <87tsxq1q5j.fsf@suse.de> (raw)
In-Reply-To: <20251215205203.1185099-9-peterx@redhat.com>
Peter Xu <peterx@redhat.com> 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 <peterx@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
next prev parent reply other threads:[~2025-12-16 14:02 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-15 20:51 [PATCH v3 00/12] KVM/hostmem: Support init-shared guest-memfd as VM backends Peter Xu
2025-12-15 20:51 ` [PATCH v3 01/12] kvm: Decouple memory attribute check from kvm_guest_memfd_supported Peter Xu
2025-12-16 12:41 ` Xiaoyao Li
2025-12-23 16:56 ` Peter Xu
2025-12-16 13:53 ` Fabiano Rosas
2025-12-23 17:02 ` Peter Xu
2026-06-02 1:10 ` Michael Roth
2025-12-15 20:51 ` [PATCH v3 02/12] kvm: Detect guest-memfd flags supported Peter Xu
2025-12-16 13:54 ` Fabiano Rosas
2026-06-02 1:29 ` Michael Roth
2025-12-15 20:51 ` [PATCH v3 03/12] kvm: Provide explicit error for kvm_create_guest_memfd() Peter Xu
2025-12-16 4:03 ` Xiaoyao Li
2025-12-16 13:55 ` Fabiano Rosas
2026-06-02 1:31 ` Michael Roth
2025-12-15 20:51 ` [PATCH v3 04/12] ramblock: Rename guest_memfd to guest_memfd_private Peter Xu
2026-06-02 1:37 ` Michael Roth
2025-12-15 20:51 ` [PATCH v3 05/12] memory: Rename RAM_GUEST_MEMFD to RAM_GUEST_MEMFD_PRIVATE Peter Xu
2025-12-16 5:49 ` Xiaoyao Li
2025-12-23 17:04 ` Peter Xu
2026-06-02 1:39 ` Michael Roth
2025-12-15 20:51 ` [PATCH v3 06/12] memory: Rename memory_region_has_guest_memfd() to *_private() Peter Xu
2026-06-02 1:40 ` Michael Roth
2025-12-15 20:51 ` [PATCH v3 07/12] hostmem: Rename guest_memfd to guest_memfd_private Peter Xu
2025-12-16 5:54 ` Xiaoyao Li
2026-06-02 18:56 ` Michael Roth
2025-12-15 20:51 ` [PATCH v3 08/12] hostmem: Support fully shared guest memfd to back a VM Peter Xu
2025-12-16 6:54 ` Xiaoyao Li
2025-12-16 14:02 ` Fabiano Rosas [this message]
2026-06-02 21:40 ` Michael Roth
2026-06-05 7:23 ` David Hildenbrand (Arm)
2026-06-05 11:23 ` David Hildenbrand (Arm)
2025-12-15 20:52 ` [PATCH v3 09/12] machine: Rename machine_require_guest_memfd() to *_private() Peter Xu
2025-12-16 6:55 ` Xiaoyao Li
2026-06-02 21:46 ` Michael Roth
2025-12-15 20:52 ` [PATCH v3 10/12] memory: Rename memory_region_init_ram_guest_memfd() " Peter Xu
2025-12-16 6:56 ` Xiaoyao Li
2026-06-02 21:49 ` Michael Roth
2025-12-15 20:52 ` [PATCH v3 11/12] tests/migration-test: Support guest-memfd init shared mem type Peter Xu
2025-12-16 14:18 ` Fabiano Rosas
2025-12-23 17:09 ` Peter Xu
2025-12-15 20:52 ` [PATCH v3 12/12] tests/migration-test: Add a precopy test for guest-memfd Peter Xu
2025-12-16 14:20 ` Fabiano Rosas
2026-06-02 22:02 ` [PATCH v3 00/12] KVM/hostmem: Support init-shared guest-memfd as VM backends Michael Roth
2026-06-03 19:27 ` Peter Xu
2026-06-04 22:36 ` Michael Roth
2026-06-05 14:57 ` Peter Xu
2026-06-08 17:59 ` Michael Roth
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