Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 11 Apr 2023 01:35:20 +0000
In-Reply-To: <9bbdc378-e66e-0a44-244b-33dffe888a2b@redhat.com> (message from
 David Hildenbrand on Mon, 3 Apr 2023 10:24:37 +0200)
Mime-Version: 1.0
Message-ID: <diqz5ya319rb.fsf@ackerleytng-cloudtop.c.googlers.com>
Subject: Re: [RFC PATCH v3 2/2] selftests: restrictedmem: Check hugepage-ness
 of shmem file backing restrictedmem fd
From:   Ackerley Tng <ackerleytng@google.com>
To:     David Hildenbrand <david@redhat.com>
Cc:     kvm@vger.kernel.org, linux-api@vger.kernel.org,
        linux-arch@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, qemu-devel@nongnu.org, aarcange@redhat.com,
        ak@linux.intel.com, akpm@linux-foundation.org, arnd@arndb.de,
        bfields@fieldses.org, bp@alien8.de, chao.p.peng@linux.intel.com,
        corbet@lwn.net, dave.hansen@intel.com, ddutile@redhat.com,
        dhildenb@redhat.com, hpa@zytor.com, hughd@google.com,
        jlayton@kernel.org, jmattson@google.com, joro@8bytes.org,
        jun.nakajima@intel.com, kirill.shutemov@linux.intel.com,
        linmiaohe@huawei.com, luto@kernel.org, mail@maciej.szmigiero.name,
        mhocko@suse.com, michael.roth@amd.com, mingo@redhat.com,
        naoya.horiguchi@nec.com, pbonzini@redhat.com, qperret@google.com,
        rppt@kernel.org, seanjc@google.com, shuah@kernel.org,
        steven.price@arm.com, tabba@google.com, tglx@linutronix.de,
        vannapurve@google.com, vbabka@suse.cz, vkuznets@redhat.com,
        wanpengli@tencent.com, wei.w.wang@intel.com, x86@kernel.org,
        yu.c.zhang@linux.intel.com
Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes
Precedence: bulk

David Hildenbrand <david@redhat.com> writes:

> On 01.04.23 01:50, Ackerley Tng wrote:
>> For memfd_restricted() calls without a userspace mount, the backing
>> file should be the shmem mount in the kernel, and the size of backing
>> pages should be as defined by system-wide shmem configuration.

>> If a userspace mount is provided, the size of backing pages should be
>> as defined in the mount.

>> Also includes negative tests for invalid inputs, including fds
>> representing read-only superblocks/mounts.


> When you talk about "hugepage" in this patch, do you mean THP or
> hugetlb? I suspect thp, so it might be better to spell that out. IIRC,
> there are plans to support actual huge pages in the future, at which
> point "hugepage" terminology could be misleading.


Thanks for pointing this out! I've replaced references to hugepage with
thp, please see RFC v4 at
https://lore.kernel.org/lkml/cover.1681176340.git.ackerleytng@google.com/T/

>> Signed-off-by: Ackerley Tng <ackerleytng@google.com>
>> ---
>>    tools/testing/selftests/Makefile              |   1 +
>>    .../selftests/restrictedmem/.gitignore        |   3 +
>>    .../testing/selftests/restrictedmem/Makefile  |  15 +
>>    .../testing/selftests/restrictedmem/common.c  |   9 +
>>    .../testing/selftests/restrictedmem/common.h  |   8 +
>>    .../restrictedmem_hugepage_test.c             | 486 ++++++++++++++++++
>>    6 files changed, 522 insertions(+)
>>    create mode 100644 tools/testing/selftests/restrictedmem/.gitignore
>>    create mode 100644 tools/testing/selftests/restrictedmem/Makefile
>>    create mode 100644 tools/testing/selftests/restrictedmem/common.c
>>    create mode 100644 tools/testing/selftests/restrictedmem/common.h
>>    create mode 100644  
>> tools/testing/selftests/restrictedmem/restrictedmem_hugepage_test.c

>> ...