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 8A58B175A8B; Sat, 23 May 2026 00:18:03 +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=1779495483; cv=none; b=uU+fO8AAAvrJMfL9kB2vvCuSyNJJKMGklTq1AMVwM8M8wwvz6Ho0863YLl/Uhzwzh1DiVut//dQOlL38d+E2JSrjzqzn/GZ3fQxP8j9HL2/KVnu6zEIuPMOOvAxVz9ZM5rwWklzMJrwFXy08CFn6j9qjGwkUj7q+/K36xDRMu5I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779495483; c=relaxed/simple; bh=mrchEoYiH8gcOjcM/Y0ZuJJOrF0TVKVwg3EtglCRqS4=; h=From:Subject:Date:Message-Id:MIME-Version:Content-Type:To:Cc; b=AgI71QPBhWsLCI8pWMhBmzf/YT2ebShuW0T5xFRk4FJ9dobliyDpydeDBMGh4qbrkx4RgUHKkEj8sSpfSPFcf9APEDNFB0KESghN2BfYe3rYrS83iC3h/yml+pHLbFcTIEtjajMLiskWanZo59cvNIWyXTkOaCe1V30jt3NWlC8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KnMDhYqf; 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="KnMDhYqf" Received: by smtp.kernel.org (Postfix) with ESMTPS id 29C9BC2BCB3; Sat, 23 May 2026 00:18:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1779495483; bh=mrchEoYiH8gcOjcM/Y0ZuJJOrF0TVKVwg3EtglCRqS4=; h=From:Subject:Date:To:Cc:Reply-To:From; b=KnMDhYqfaTckB4tG03Go7DB2WOfwRVprMCwPDRqQj4vCXGkTR630fLQ3Zrmawypv/ XCRdnShuBuGODkH6LmqHNWVIxGKQMsmszBwzsVtVLzw/ouQFsvAhyCtJjP5/ejToj3 ref658+glEyNSGczMLO8cjApCn1EUi6qTYFsdm6fIRpfbP4IuZH96Dv5CG/5gxwpcL ILYC00k2ULzqk/nd7QfkeYJatCskc6ari5jTrXvgjnllNFPWdAe6lh0QrVSZg/lDv4 i2DiDiiIfSonycuO+oOL7ln3MbOfCZ0gRm9U0JZBOpR+tQ+emSS+TQR8Hz8ypmoe/S evQoCEfAG59Cw== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id 04461CD4F3D; Sat, 23 May 2026 00:18:03 +0000 (UTC) From: Ackerley Tng via B4 Relay Subject: [PATCH v7 00/42] guest_memfd: In-place conversion support Date: Fri, 22 May 2026 17:17:42 -0700 Message-Id: <20260522-gmem-inplace-conversion-v7-0-2f0fae496530@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIACfyEGoC/3XRS2rDMBAG4KsYratWlqyXV71H6UKSR45o/Ijti JSQu3ccU9ISvBEMzHy/mLmSGaYEM6mLK5kgpzkNPRb6pSDh4PoWaGqwJpxxxTiXtO2go6kfjy4 ADUOfYVpnqG9Y4xthtRSO4PQ4QUyXu/zxibV3M1A/uT4cVu8rd289XJa19ZDmZZi+73/IYh3Y4 kQpduOyoIzKGEruNINg7Hs7DO0RXsPQkTUvV38grvahCiHAtghWshibJ0g+oIqbfUgi1BjFTAg xOM6fIPWAJNP7kELIls5LZ3xpXfUPum27neB0xmMt24Ift6qLzeec4vrpDHnLGYd5wWc8H90C1 AnlIerIlDV15uT3PpjQpaUuvI4erCt9tAAqWKWxWzdCqeCkCQIXH0tjNH7n9gMwRNTzQwIAAA= = X-Change-ID: 20260225-gmem-inplace-conversion-bd0dbd39753a To: aik@amd.com, andrew.jones@linux.dev, binbin.wu@linux.intel.com, brauner@kernel.org, chao.p.peng@linux.intel.com, david@kernel.org, ira.weiny@intel.com, jmattson@google.com, jthoughton@google.com, michael.roth@amd.com, oupton@kernel.org, pankaj.gupta@amd.com, qperret@google.com, rick.p.edgecombe@intel.com, rientjes@google.com, shivankg@amd.com, steven.price@arm.com, tabba@google.com, willy@infradead.org, wyihan@google.com, yan.y.zhao@intel.com, forkloop@google.com, pratyush@kernel.org, suzuki.poulose@arm.com, aneesh.kumar@kernel.org, liam@infradead.org, Paolo Bonzini , Sean Christopherson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Jonathan Corbet , Shuah Khan , Shuah Khan , Vishal Annapurve , Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Youngjun Park , Qi Zheng , Shakeel Butt , Kiryl Shutsemau , Jason Gunthorpe , Vlastimil Babka Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev, Ackerley Tng X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1779495480; l=9831; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=mrchEoYiH8gcOjcM/Y0ZuJJOrF0TVKVwg3EtglCRqS4=; b=XctpTIWSLMlMA3C7v6mhY/pm36LJUK3SBRjcBPRKNzNdKcTniGdvs1LuwFMY3k+I5WF0dzQcp k3yEwlR8BjeDL3TAujsvtIGTZcbc8C/WIajETzDAPpVjqswfqhi8zTg X-Developer-Key: i=ackerleytng@google.com; a=ed25519; pk=sAZDYXdm6Iz8FHitpHeFlCMXwabodTm7p8/3/8xUxuU= X-Endpoint-Received: by B4 Relay for ackerleytng@google.com/20260225 with auth_id=649 X-Original-From: Ackerley Tng Reply-To: ackerleytng@google.com This is v7 of guest_memfd in-place conversion support. Up till now, guest_memfd supports the entire inode worth of memory being used as all-shared, or all-private. CoCo VMs may request guest memory to be converted between private and shared states, and the only way to support that currently would be to have the userspace VMM provide two sources of backing memory from completely different areas of physical memory. pKVM has a use case for in-place sharing: the guest and host may be cooperating on given data, and pKVM doesn't protect data through encryption, so copying that given data between different areas of physical memory as part of conversions would be unnecessary work. This series also serves as a foundation for guest_memfd huge page support. Now, guest_memfd only supports PAGE_SIZE pages, so if two sources of backing memory are used, the userspace VMM could maintain a steady total memory utilized by punching out the pages that are not used. When huge pages are available in guest_memfd, even if the backing memory source supports hole punching within a huge page, punching out pages to maintain the total memory utilized by a VM would be introducing lots of fragmentation. In-place conversion avoids fragmentation by allowing the same physical memory to be used for both shared and private memory, with guest_memfd tracks the shared/private status of all the pages at a per-page granularity. The central principle, which guest_memfd continues to uphold, is that any guest-private page will not be mappable to host userspace. All pages will be mmap()-able in host userspace, but accesses to guest-private pages (as tracked by guest_memfd) will result in a SIGBUS. This series introduces a guest_memfd ioctl (not kvm, vm or vcpu, but guest_memfd ioctl) that allows userspace to set memory attributes (shared/private) directly through the guest_memfd. This is the appropriate interface because shared/private-ness is a property of memory and hence the request should be sent directly to the memory provider - guest_memfd. Tested with both CONFIG_KVM_VM_MEMORY_ATTRIBUTES enabled and disabled: + tools/testing/selftests/kvm/guest_memfd_test.c + tools/testing/selftests/kvm/pre_fault_memory_test.c + tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c + tools/testing/selftests/kvm/x86/private_mem_conversions_test.c + tools/testing/selftests/kvm/x86/private_mem_conversions_test.sh + tools/testing/selftests/kvm/x86/private_mem_kvm_exits_test.c Updates for this revision: + Picked up Reviewed-bys from Fuad + Addressed Fuad, Sean and Sashiko's comments Regarding the issue where guest_memfd_conversions_test, which uses the kselftest framework, doesn't perform teardown on assertion failure. I think we can have that fixed separately from this series? Please see proposal [9]. TODOs + Test with TDX selftests. We're in the process of rebasing TDX selftests on this series and will post updates when that's tested. This series is based on kvm/next, and here's the tree for your convenience: https://github.com/googleprodkernel/linux-cc/commits/guest_memfd-inplace-conversion-v7 Older series: + RFCv6 is at [10] + RFCv5 is at [8] + RFCv4 is at [7] + RFCv3 is at [6] + RFCv2 is at [5] + RFCv1 is at [4] + Previous versions of this feature, part of other series, are available at [1][2][3]. [1] https://lore.kernel.org/all/bd163de3118b626d1005aa88e71ef2fb72f0be0f.1726009989.git.ackerleytng@google.com/ [2] [3] https://lore.kernel.org/all/b784326e9ccae6a08388f1bf39db70a2204bdc51.1747264138.git.ackerleytng@google.com/ [4] https://lore.kernel.org/all/cover.1760731772.git.ackerleytng@google.com/T/ [5] https://lore.kernel.org/all/cover.1770071243.git.ackerleytng@google.com/T/ [6] https://lore.kernel.org/r/20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com/T/ [7] https://lore.kernel.org/all/20260326-gmem-inplace-conversion-v4-0-e202fe950ffd@google.com/T/ [8] https://lore.kernel.org/r/20260428-gmem-inplace-conversion-v5-0-d8608ccfca22@google.com [9] https://lore.kernel.org/all/20260414-selftest-global-metadata-v1-0-fd223922bc57@google.com/T/ [10] https://lore.kernel.org/r/20260507-gmem-inplace-conversion-v6-0-91ab5a8b19a4@google.com Signed-off-by: Ackerley Tng --- Ackerley Tng (24): KVM: guest_memfd: Update kvm_gmem_populate() to use gmem attributes KVM: guest_memfd: Only prepare folios for private pages KVM: Move kvm_supported_mem_attributes() to kvm_host.h KVM: guest_memfd: Add base support for KVM_SET_MEMORY_ATTRIBUTES2 KVM: guest_memfd: Ensure pages are not in use before conversion KVM: guest_memfd: Call arch invalidate hooks on conversion KVM: guest_memfd: Return early if range already has requested attributes KVM: guest_memfd: Advertise KVM_SET_MEMORY_ATTRIBUTES2 ioctl KVM: guest_memfd: Handle lru_add fbatch refcounts during conversion safety check KVM: guest_memfd: Use actual size for invalidation in kvm_gmem_release() KVM: guest_memfd: Determine invalidation filter from memory attributes KVM: TDX: Make source page optional for KVM_TDX_INIT_MEM_REGION KVM: selftests: Test basic single-page conversion flow KVM: selftests: Test conversion flow when INIT_SHARED KVM: selftests: Test conversion precision in guest_memfd KVM: selftests: Test conversion before allocation KVM: selftests: Convert with allocated folios in different layouts KVM: selftests: Test that truncation does not change shared/private status KVM: selftests: Test conversion with elevated page refcount KVM: selftests: Reset shared memory after hole-punching KVM: selftests: Provide function to look up guest_memfd details from gpa KVM: selftests: Make TEST_EXPECT_SIGBUS thread-safe KVM: selftests: Update private_mem_conversions_test to mmap() guest_memfd KVM: selftests: Add script to exercise private_mem_conversions_test Michael Roth (1): KVM: SEV: Make 'uaddr' parameter optional for KVM_SEV_SNP_LAUNCH_UPDATE Sean Christopherson (17): KVM: guest_memfd: Introduce per-gmem attributes, use to guard user mappings KVM: Rename KVM_GENERIC_MEMORY_ATTRIBUTES to KVM_VM_MEMORY_ATTRIBUTES KVM: Enumerate support for PRIVATE memory iff kvm_arch_has_private_mem is defined KVM: Stub in ability to disable per-VM memory attribute tracking KVM: guest_memfd: Wire up kvm_get_memory_attributes() to per-gmem attributes KVM: Move KVM_VM_MEMORY_ATTRIBUTES config definition to x86 KVM: Let userspace disable per-VM mem attributes, enable per-gmem attributes KVM: guest_memfd: Enable INIT_SHARED on guest_memfd for x86 Coco VMs KVM: selftests: Create gmem fd before "regular" fd when adding memslot KVM: selftests: Rename guest_memfd{,_offset} to gmem_{fd,offset} KVM: selftests: Add support for mmap() on guest_memfd in core library KVM: selftests: Add selftests global for guest memory attributes capability KVM: selftests: Add helpers for calling ioctls on guest_memfd KVM: selftests: Test that shared/private status is consistent across processes KVM: selftests: Provide common function to set memory attributes KVM: selftests: Check fd/flags provided to mmap() when setting up memslot KVM: selftests: Update private memory exits test to work with per-gmem attributes Documentation/virt/kvm/api.rst | 78 +++- .../virt/kvm/x86/amd-memory-encryption.rst | 15 +- Documentation/virt/kvm/x86/intel-tdx.rst | 4 + arch/x86/include/asm/kvm_host.h | 2 +- arch/x86/kvm/Kconfig | 15 +- arch/x86/kvm/mmu/mmu.c | 4 +- arch/x86/kvm/svm/sev.c | 18 +- arch/x86/kvm/vmx/tdx.c | 11 +- arch/x86/kvm/x86.c | 13 +- include/linux/kvm_host.h | 53 ++- include/trace/events/kvm.h | 4 +- include/uapi/linux/kvm.h | 16 + mm/swap.c | 2 + tools/testing/selftests/kvm/Makefile.kvm | 5 + tools/testing/selftests/kvm/include/kvm_util.h | 136 +++++- tools/testing/selftests/kvm/include/test_util.h | 34 +- .../selftests/kvm/kvm_has_gmem_attributes.c | 17 + tools/testing/selftests/kvm/lib/kvm_util.c | 141 +++--- tools/testing/selftests/kvm/lib/test_util.c | 7 - .../kvm/x86/guest_memfd_conversions_test.c | 488 +++++++++++++++++++++ .../kvm/x86/private_mem_conversions_test.c | 53 ++- .../kvm/x86/private_mem_conversions_test.sh | 128 ++++++ .../selftests/kvm/x86/private_mem_kvm_exits_test.c | 36 +- virt/kvm/Kconfig | 3 +- virt/kvm/guest_memfd.c | 460 +++++++++++++++++-- virt/kvm/kvm_main.c | 82 +++- 26 files changed, 1633 insertions(+), 192 deletions(-) --- base-commit: b7fbe9a1bf9ee6c967ef77d366ca58c35fcf1887 change-id: 20260225-gmem-inplace-conversion-bd0dbd39753a prerequisite-change-id: 20260522-fix-sev-gmem-post-populate-a36bef7f0698:v2 prerequisite-patch-id: 0d1feef8af7aa3471735869080aefa58b254ed0d prerequisite-patch-id: f64ff55d6fe8d399e720a570fd83cc47bf12ac15 prerequisite-patch-id: 8c52920dd7f65859cbe804c787a9293b33266a3a prerequisite-patch-id: 95018daf73833296a045c91cfb55cd9f53886dec prerequisite-patch-id: bcfd440d79bb9f59f41e3244c4392da4c95cd932 Best regards, -- Ackerley Tng