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From: Peter Xu <peterx@redhat.com>
To: Nikita Kalyazin <kalyazin@amazon.com>
Cc: Mike Rapoport <rppt@kernel.org>,
	linux-mm@kvack.org, Andrea Arcangeli <aarcange@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Baolin Wang <baolin.wang@linux.alibaba.com>,
	David Hildenbrand <david@redhat.com>,
	Hugh Dickins <hughd@google.com>,
	"Liam R. Howlett" <Liam.Howlett@oracle.com>,
	Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
	Michal Hocko <mhocko@suse.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	Shuah Khan <shuah@kernel.org>,
	Suren Baghdasaryan <surenb@google.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	linux-kselftest@vger.kernel.org
Subject: Re: [RFC PATCH 0/4] mm, kvm: add guest_memfd support for uffd minor faults
Date: Mon, 17 Nov 2025 14:39:06 -0500	[thread overview]
Message-ID: <aRt52tDCh72ytIp1@x1.local> (raw)
In-Reply-To: <a5531d06-dd11-402b-a701-a7c6a62186a7@amazon.com>

On Mon, Nov 17, 2025 at 05:55:46PM +0000, Nikita Kalyazin wrote:
> In our use case, Firecracker snapshot-restore using UFFD [1], we will use
> UFFD minor/continue to respond to guest_memfd faults in user mappings
> primarily due to VMM accesses that are required for PV (virtio) device
> emulation and also KVM accesses when decoding MMIO operations on x86.

I'm curious if firecracker plans to support live snapshot save.  When with
something like ioctls_supported flags, guest-memfd can declare support for
wr-protect support easily too, and synchronous userfaultfd wr-protect traps
will be an efficient way to do live save.

I'm guessing it's not an immediate demand now or it would have been asked
already supporting both MINOR and WP, but I just want to raise this
question.  Qemu already supports live snapshot save, so it'll always be
good gmem can also support wp at some point, but it can be done later too.

Thanks,

-- 
Peter Xu



  reply	other threads:[~2025-11-17 19:39 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-11-17 11:46 [RFC PATCH 0/4] mm, kvm: add guest_memfd support for uffd minor faults Mike Rapoport
2025-11-17 11:46 ` [RFC PATCH 1/4] userfaultfd: move vma_can_userfault out of line Mike Rapoport
2025-11-17 17:00   ` David Hildenbrand (Red Hat)
2025-11-17 11:46 ` [RFC PATCH 2/4] userfaultfd, shmem: use a VMA callback to handle UFFDIO_CONTINUE Mike Rapoport
2025-11-17 17:08   ` David Hildenbrand (Red Hat)
2025-11-21 11:52     ` Mike Rapoport
2025-11-17 11:46 ` [RFC PATCH 3/4] userfaultfd, guest_memfd: support userfault minor mode in guest_memfd Mike Rapoport
2025-11-18 16:41   ` David Hildenbrand (Red Hat)
2025-11-21 11:59     ` Mike Rapoport
2025-11-17 11:46 ` [RFC PATCH 4/4] KVM: selftests: test userfaultfd minor for guest_memfd Mike Rapoport
2025-11-17 17:55 ` [RFC PATCH 0/4] mm, kvm: add guest_memfd support for uffd minor faults Nikita Kalyazin
2025-11-17 19:39   ` Peter Xu [this message]
2025-11-19 17:35     ` Nikita Kalyazin

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