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Fri, 16 Jan 2026 15:00:59 +0000 (UTC) X-Farcaster-Flow-ID: d65bbded-3f2b-45ea-90e0-dd1ca16777be Received: from EX19D005EUB003.ant.amazon.com (10.252.51.31) by EX19MTAEUA002.ant.amazon.com (10.252.50.124) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.35; Fri, 16 Jan 2026 15:00:58 +0000 Received: from [192.168.12.13] (10.106.82.9) by EX19D005EUB003.ant.amazon.com (10.252.51.31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.35; Fri, 16 Jan 2026 15:00:54 +0000 Message-ID: <04173297-518d-460a-be9f-502d32cbe509@amazon.com> Date: Fri, 16 Jan 2026 15:00:53 +0000 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Reply-To: Subject: Re: [PATCH v9 09/13] KVM: selftests: set KVM_MEM_GUEST_MEMFD in vm_mem_add() if guest_memfd != -1 To: Ackerley Tng , "Kalyazin, Nikita" , "kvm@vger.kernel.org" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "kvmarm@lists.linux.dev" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "bpf@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , "kernel@xen0n.name" , "linux-riscv@lists.infradead.org" , "linux-s390@vger.kernel.org" , "loongarch@lists.linux.dev" CC: "pbonzini@redhat.com" , "corbet@lwn.net" , "maz@kernel.org" , "oupton@kernel.org" , "joey.gouly@arm.com" , "suzuki.poulose@arm.com" , "yuzenghui@huawei.com" , "catalin.marinas@arm.com" , "will@kernel.org" , "seanjc@google.com" , "tglx@linutronix.de" , "mingo@redhat.com" , "bp@alien8.de" , "dave.hansen@linux.intel.com" , "x86@kernel.org" , "hpa@zytor.com" , "luto@kernel.org" , "peterz@infradead.org" , "willy@infradead.org" , "akpm@linux-foundation.org" , "david@kernel.org" , "lorenzo.stoakes@oracle.com" , "Liam.Howlett@oracle.com" , "vbabka@suse.cz" , "rppt@kernel.org" , "surenb@google.com" , "mhocko@suse.com" , "ast@kernel.org" , "daniel@iogearbox.net" , "andrii@kernel.org" , "martin.lau@linux.dev" , "eddyz87@gmail.com" , "song@kernel.org" , "yonghong.song@linux.dev" , "john.fastabend@gmail.com" , "kpsingh@kernel.org" , "sdf@fomichev.me" , "haoluo@google.com" , "jolsa@kernel.org" , "jgg@ziepe.ca" , "jhubbard@nvidia.com" , "peterx@redhat.com" , "jannh@google.com" , "pfalcato@suse.de" , "shuah@kernel.org" , "riel@surriel.com" , "ryan.roberts@arm.com" , "jgross@suse.com" , "yu-cheng.yu@intel.com" , "kas@kernel.org" , "coxu@redhat.com" , "kevin.brodsky@arm.com" , "maobibo@loongson.cn" , "prsampat@amd.com" , "mlevitsk@redhat.com" , "jmattson@google.com" , "jthoughton@google.com" , "agordeev@linux.ibm.com" , "alex@ghiti.fr" , "aou@eecs.berkeley.edu" , "borntraeger@linux.ibm.com" , "chenhuacai@kernel.org" , "dev.jain@arm.com" , "gor@linux.ibm.com" , "hca@linux.ibm.com" , "Jonathan.Cameron@huawei.com" , "palmer@dabbelt.com" , "pjw@kernel.org" , "shijie@os.amperecomputing.com" , "svens@linux.ibm.com" , "thuth@redhat.com" , "wyihan@google.com" , "yang@os.amperecomputing.com" , "vannapurve@google.com" , "jackmanb@google.com" , "aneesh.kumar@kernel.org" , "patrick.roy@linux.dev" , "Thomson, Jack" , "Itazuri, Takahiro" , "Manwaring, Derek" , "Cali, Marco" References: <20260114134510.1835-1-kalyazin@amazon.com> <20260114134510.1835-10-kalyazin@amazon.com> Content-Language: en-US From: Nikita Kalyazin Autocrypt: addr=kalyazin@amazon.com; keydata= xjMEY+ZIvRYJKwYBBAHaRw8BAQdA9FwYskD/5BFmiiTgktstviS9svHeszG2JfIkUqjxf+/N JU5pa2l0YSBLYWx5YXppbiA8a2FseWF6aW5AYW1hem9uLmNvbT7CjwQTFggANxYhBGhhGDEy BjLQwD9FsK+SyiCpmmTzBQJnrNfABQkFps9DAhsDBAsJCAcFFQgJCgsFFgIDAQAACgkQr5LK IKmaZPOpfgD/exazh4C2Z8fNEz54YLJ6tuFEgQrVQPX6nQ/PfQi2+dwBAMGTpZcj9Z9NvSe1 CmmKYnYjhzGxzjBs8itSUvWIcMsFzjgEY+ZIvRIKKwYBBAGXVQEFAQEHQCqd7/nb2tb36vZt ubg1iBLCSDctMlKHsQTp7wCnEc4RAwEIB8J+BBgWCAAmFiEEaGEYMTIGMtDAP0Wwr5LKIKma ZPMFAmes18AFCQWmz0MCGwwACgkQr5LKIKmaZPNTlQEA+q+rGFn7273rOAg+rxPty0M8lJbT i2kGo8RmPPLu650A/1kWgz1AnenQUYzTAFnZrKSsXAw5WoHaDLBz9kiO5pAK In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: EX19D010EUA004.ant.amazon.com (10.252.50.94) To EX19D005EUB003.ant.amazon.com (10.252.51.31) On 15/01/2026 19:39, Ackerley Tng wrote: > "Kalyazin, Nikita" writes: > >> From: Patrick Roy >> >> Have vm_mem_add() always set KVM_MEM_GUEST_MEMFD in the memslot flags if >> a guest_memfd is passed in as an argument. This eliminates the >> possibility where a guest_memfd instance is passed to vm_mem_add(), but >> it ends up being ignored because the flags argument does not specify >> KVM_MEM_GUEST_MEMFD at the same time. >> >> This makes it easy to support more scenarios in which no vm_mem_add() is >> not passed a guest_memfd instance, but is expected to allocate one. >> Currently, this only happens if guest_memfd == -1 but flags & >> KVM_MEM_GUEST_MEMFD != 0, but later vm_mem_add() will gain support for >> loading the test code itself into guest_memfd (via >> GUEST_MEMFD_FLAG_MMAP) if requested via a special >> vm_mem_backing_src_type, at which point having to make sure the src_type >> and flags are in-sync becomes cumbersome. >> >> Signed-off-by: Patrick Roy >> Signed-off-by: Nikita Kalyazin >> --- >> tools/testing/selftests/kvm/lib/kvm_util.c | 24 +++++++++++++--------- >> 1 file changed, 14 insertions(+), 10 deletions(-) >> >> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c >> index 8279b6ced8d2..56ddbca91850 100644 >> --- a/tools/testing/selftests/kvm/lib/kvm_util.c >> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c >> @@ -1057,21 +1057,25 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type, >> >> region->backing_src_type = src_type; >> >> - if (flags & KVM_MEM_GUEST_MEMFD) { >> - if (guest_memfd < 0) { >> + if (guest_memfd < 0) { >> + if (flags & KVM_MEM_GUEST_MEMFD) { >> uint32_t guest_memfd_flags = 0; >> TEST_ASSERT(!guest_memfd_offset, >> "Offset must be zero when creating new guest_memfd"); >> guest_memfd = vm_create_guest_memfd(vm, mem_size, guest_memfd_flags); >> - } else { >> - /* >> - * Install a unique fd for each memslot so that the fd >> - * can be closed when the region is deleted without >> - * needing to track if the fd is owned by the framework >> - * or by the caller. >> - */ >> - guest_memfd = kvm_dup(guest_memfd); >> } >> + } else { >> + /* >> + * Install a unique fd for each memslot so that the fd >> + * can be closed when the region is deleted without >> + * needing to track if the fd is owned by the framework >> + * or by the caller. >> + */ >> + guest_memfd = kvm_dup(guest_memfd); >> + } >> + >> + if (guest_memfd > 0) { > > Might 0 turn out to be a valid return from dup() for a guest_memfd? Yes, you're right, it isn't impossible. Thanks! > >> + flags |= KVM_MEM_GUEST_MEMFD; >> >> region->region.guest_memfd = guest_memfd; >> region->region.guest_memfd_offset = guest_memfd_offset; > > Refactoring vm_mem_add() (/* FIXME: This thing needs to be ripped apart > and rewritten. */) should probably be a separate patch series, but I'd > like to take this opportunity to ask: Sean, what do you have in mind for > the rewritten version? > > Would it be something like struct vm_shape, where there are default > mem_shapes, and the shapes get validated and then passed to > vm_mem_add()? > >> -- >> 2.50.1