From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DD6242820A4; Sun, 23 Nov 2025 10:27:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763893637; cv=none; b=aMPCSXrLUCfk9OWUcyFYXtAQJ0A+aWSGMolSn9I/E0IXnquI/HhdfxIIjzNoal+LfYizGsaCeVxGsrqZybCNN25n0eFfzGvSSSU6RrnHcQPKRGScAcEWmpl9MAmokPmAZv2zRyglmriRm7ZIsxuwgCJ0XWeYcikIFmXPPSB27jE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763893637; c=relaxed/simple; bh=uQ+XNRc47lHfiREiaIwuPCqXlDMz96Y+Ua7eszfUoWw=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=llBowd9+opYXemxdlDL/APQVe/D/qiSl0WrHmowqfF974OtCkoef5QonafR/Vkm/Fpeu56XXTqFBfvoyWmPV7LLv9huiOxPb3cZjScxizsmIcINz+A2PY43v6M/YsvTqQ7OqnBACGnAGiqpOmQ6yGKmWfMr/vmpTPmIdKs+0W5g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=miOLm7bo; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="miOLm7bo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 254B9C113D0; Sun, 23 Nov 2025 10:27:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763893636; bh=uQ+XNRc47lHfiREiaIwuPCqXlDMz96Y+Ua7eszfUoWw=; h=From:To:Cc:Subject:Date:From; b=miOLm7boejNLZkZWl7MecUiBUNqyViv6anj+8bxooagNb3kdikR5sNpE/yUgJ2OeH LOxKOzOxo+XdaqrY81kTYt5phmRtUbIqvbTj8/ytq4XGAu/bwVOtY6iqyr34WINb42 rTtculAEvWMXO36PnaApcYiJF4kYrM+LiBbq/y/YHeh5RZ4wvWG4JhZmSPVvZTC/y3 JPtMO7WwXssH5azIRYZ+l7z7Nopi7xlVVWLRWXfA9gZU0zAAqq6BbEecaBNL0kJZK4 rjSc5qQhpyQkvTVGUuxCC8aRYwVcSOVyei0hy7xwXcU2ht25mTlFMsVaZ0tkQPhMIW r8fJUHurTqBLg== From: Mike Rapoport To: linux-mm@kvack.org Cc: Andrea Arcangeli , Andrew Morton , Axel Rasmussen , Baolin Wang , David Hildenbrand , Hugh Dickins , James Houghton , "Liam R. Howlett" , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Nikita Kalyazin , Paolo Bonzini , Peter Xu , Sean Christopherson , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH 0/5] mm, kvm: add guest_memfd support for uffd minor faults Date: Sun, 23 Nov 2025 12:27:02 +0200 Message-ID: <20251123102707.559422-1-rppt@kernel.org> X-Mailer: git-send-email 2.50.1 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: "Mike Rapoport (Microsoft)" Hi, These patches allow guest_memfd to notify userspace about minor page faults using userfaultfd and let userspace to resolve these page faults using UFFDIO_CONTINUE. To allow UFFDIO_CONTINUE outside of the core mm I added a get_shmem_folio() callback to vm_ops that allows an address space backing a VMA to return a folio that exists in it's page cache (patch 2) In order for guest_memfd to notify userspace about page faults, there is a new VM_FAULT_UFFD_MINOR that a ->fault() handler can return to inform the page fault handler that it needs to call handle_userfault() to complete the fault (patch 3). Patch 4 plumbs these new goodies into guest_memfd. This series is the minimal change I've been able to come up with to allow integration of guest_memfd with uffd and while refactoring uffd and making mfill_atomic() flow more linear would have been a nice improvement, it's way out of the scope of enabling uffd with guest_memfd. v2 changes: * Introduce VM_FAULF_UFFD_MINOR to avoid exporting handle_userfault() * Simplify vma_can_mfill_atomic() * Rename get_pagecache_folio() to get_shared_folio() and use inode instead of vma as its argument v1: https://lore.kernel.org/all/20251117114631.2029447-1-rppt@kernel.org Mike Rapoport (Microsoft) (4): userfaultfd: move vma_can_userfault out of line userfaultfd, shmem: use a VMA callback to handle UFFDIO_CONTINUE mm: introduce VM_FAULT_UFFD_MINOR fault reason guest_memfd: add support for userfaultfd minor mode Nikita Kalyazin (1): KVM: selftests: test userfaultfd minor for guest_memfd include/linux/mm.h | 9 ++ include/linux/mm_types.h | 3 + include/linux/userfaultfd_k.h | 36 +----- mm/memory.c | 2 + mm/shmem.c | 21 +++- mm/userfaultfd.c | 80 +++++++++++--- .../testing/selftests/kvm/guest_memfd_test.c | 103 ++++++++++++++++++ virt/kvm/guest_memfd.c | 29 +++++ 8 files changed, 232 insertions(+), 51 deletions(-) base-commit: 6a23ae0a96a600d1d12557add110e0bb6e32730c -- 2.50.1