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Date: Mon, 15 Feb 2021 10:13:50 +0100 From: Michal Hocko <mhocko@...e.com> To: James Bottomley <jejb@...ux.ibm.com> Cc: David Hildenbrand <david@...hat.com>, Mike Rapoport <rppt@...nel.org>, Mike Rapoport <rppt@...ux.ibm.com>, Andrew Morton <akpm@...ux-foundation.org>, Alexander Viro <viro@...iv.linux.org.uk>, Andy Lutomirski <luto@...nel.org>, Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>, Catalin Marinas <catalin.marinas@....com>, Christopher Lameter <cl@...ux.com>, Dan Williams <dan.j.williams@...el.com>, Dave Hansen <dave.hansen@...ux.intel.com>, Elena Reshetova <elena.reshetova@...el.com>, "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>, "Kirill A. Shutemov" <kirill@...temov.name>, Matthew Wilcox <willy@...radead.org>, Mark Rutland <mark.rutland@....com>, Michael Kerrisk <mtk.manpages@...il.com>, Palmer Dabbelt <palmer@...belt.com>, Paul Walmsley <paul.walmsley@...ive.com>, Peter Zijlstra <peterz@...radead.org>, Rick Edgecombe <rick.p.edgecombe@...el.com>, Roman Gushchin <guro@...com>, Shakeel Butt <shakeelb@...gle.com>, Shuah Khan <shuah@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Tycho Andersen <tycho@...ho.ws>, Will Deacon <will@...nel.org>, linux-api@...r.kernel.org, linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, linux-nvdimm@...ts.01.org, linux-riscv@...ts.infradead.org, x86@...nel.org, Hagen Paul Pfeifer <hagen@...u.net>, Palmer Dabbelt <palmerdabbelt@...gle.com> Subject: Re: [PATCH v17 07/10] mm: introduce memfd_secret system call to create "secret" memory areas On Sun 14-02-21 11:21:02, James Bottomley wrote: > On Sun, 2021-02-14 at 10:58 +0100, David Hildenbrand wrote: > [...] > > > And here we come to the question "what are the differences that > > > justify a new system call?" and the answer to this is very > > > subjective. And as such we can continue bikeshedding forever. > > > > I think this fits into the existing memfd_create() syscall just fine, > > and I heard no compelling argument why it shouldn‘t. That‘s all I can > > say. > > OK, so let's review history. In the first two incarnations of the > patch, it was an extension of memfd_create(). The specific objection > by Kirill Shutemov was that it doesn't share any code in common with > memfd and so should be a separate system call: > > https://lore.kernel.org/linux-api/20200713105812.dnwtdhsuyj3xbh4f@box/ Thanks for the pointer. But this argument hasn't been challenged at all. It hasn't been brought up that the overlap would be considerable higher by the hugetlb/sealing support. And so far nobody has claimed those combinations as unviable. > The other objection raised offlist is that if we do use memfd_create, > then we have to add all the secret memory flags as an additional ioctl, > whereas they can be specified on open if we do a separate system call. > The container people violently objected to the ioctl because it can't > be properly analysed by seccomp and much preferred the syscall version. > > Since we're dumping the uncached variant, the ioctl problem disappears > but so does the possibility of ever adding it back if we take on the > container peoples' objection. This argues for a separate syscall > because we can add additional features and extend the API with flags > without causing anti-ioctl riots. I am sorry but I do not understand this argument. What kind of flags are we talking about and why would that be a problem with memfd_create interface? Could you be more specific please? -- Michal Hocko SUSE Labs
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