From: David Hildenbrand <david@redhat.com>
To: jejb@linux.ibm.com, Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>,
Mike Rapoport <rppt@linux.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Andy Lutomirski <luto@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Borislav Petkov <bp@alien8.de>,
Catalin Marinas <catalin.marinas@arm.com>,
Christopher Lameter <cl@linux.com>,
Dan Williams <dan.j.williams@intel.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Elena Reshetova <elena.reshetova@intel.com>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Matthew Wilcox <willy@infradead.org>,
Mark Rutland <mark.rutland@arm.com>,
Michael Kerrisk <mtk.manpages@gmail.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Peter Zijlstra <peterz@infradead.org>,
Rick Edgecombe <rick.p.edgecombe@intel.com>,
Roman Gushchin <guro@fb.com>, Shakeel Butt <shakeelb@google.com>,
Shuah Khan <shuah@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Tycho Andersen <tycho@tycho.ws>, Will Deacon <will@kernel.org>,
linux-api@vger.kernel.org, linux-arch@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
linux-nvdimm@lists.01.org, linux-riscv@lists.infradead.org,
x86@kernel.org, Hagen Paul Pfeifer <hagen@jauu.net>,
Palmer Dabbelt <palmerdabbelt@google.com>
Subject: Re: [PATCH v17 07/10] mm: introduce memfd_secret system call to create "secret" memory areas
Date: Tue, 16 Feb 2021 18:16:36 +0100 [thread overview]
Message-ID: <5a8567a9-6940-c23f-0927-e4b5c5db0d5e@redhat.com> (raw)
In-Reply-To: <000cfaa0a9a09f07c5e50e573393cda301d650c9.camel@linux.ibm.com>
>> For the other parts, the question is what we actually want to let
>> user space configure.
>>
>> Being able to specify "Very secure" "maximum secure" "average
>> secure" all doesn't really make sense to me.
>
> Well, it doesn't to me either unless the user feels a cost/benefit, so
> if max cost $100 per invocation and average cost nothing, most people
> would chose average unless they had a very good reason not to. In your
> migratable model, if we had separate limits for non-migratable and
> migratable, with non-migratable being set low to prevent exhaustion,
> max secure becomes a highly scarce resource, whereas average secure is
> abundant then having the choice might make sense.
I hope that we can find a way to handle the migration part internally.
Especially, because Mike wants the default to be "as secure as
possible", so if there is a flag, it would have to be an opt-out flag.
I guess as long as we don't temporarily map it into the "owned" location
in the direct map shared by all VCPUs we are in a good positon. But this
needs more thought, of course.
>
>> The discussion regarding migratability only really popped up because
>> this is a user-visible thing and not being able to migrate can be a
>> real problem (fragmentation, ZONE_MOVABLE, ...).
>
> I think the biggest use will potentially come from hardware
> acceleration. If it becomes simple to add say encryption to a secret
> page with no cost, then no flag needed. However, if we only have a
> limited number of keys so once we run out no more encrypted memory then
> it becomes a costly resource and users might want a choice of being
> backed by encryption or not.
Right. But wouldn't HW support with configurable keys etc. need more
syscall parameters (meaning, even memefd_secret() as it is would not be
sufficient?). I suspect the simplistic flag approach might not be
sufficient. I might be wrong because I have no clue about MKTME and friends.
Anyhow, I still think extending memfd_create() might just be good enough
- at least for now. Things like HW support might have requirements we
don't even know yet and that we cannot even model in memfd_secret()
right now.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2021-02-16 17:17 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-08 8:49 [PATCH v17 00/10] mm: introduce memfd_secret system call to create "secret" memory areas Mike Rapoport
2021-02-08 8:49 ` [PATCH v17 01/10] mm: add definition of PMD_PAGE_ORDER Mike Rapoport
2021-02-08 8:49 ` [PATCH v17 02/10] mmap: make mlock_future_check() global Mike Rapoport
2021-02-08 8:49 ` [PATCH v17 03/10] riscv/Kconfig: make direct map manipulation options depend on MMU Mike Rapoport
2021-02-08 8:49 ` [PATCH v17 04/10] set_memory: allow set_direct_map_*_noflush() for multiple pages Mike Rapoport
2021-02-08 8:49 ` [PATCH v17 05/10] set_memory: allow querying whether set_direct_map_*() is actually enabled Mike Rapoport
2021-02-08 8:49 ` [PATCH v17 06/10] arm64: kfence: fix header inclusion Mike Rapoport
2021-02-08 8:49 ` [PATCH v17 07/10] mm: introduce memfd_secret system call to create "secret" memory areas Mike Rapoport
2021-02-08 10:49 ` Michal Hocko
2021-02-08 21:26 ` Mike Rapoport
2021-02-09 8:47 ` Michal Hocko
2021-02-09 9:09 ` Mike Rapoport
2021-02-09 13:17 ` Michal Hocko
2021-02-11 7:13 ` Mike Rapoport
2021-02-11 8:39 ` Michal Hocko
2021-02-11 9:01 ` David Hildenbrand
2021-02-11 9:38 ` Michal Hocko
2021-02-11 9:48 ` David Hildenbrand
2021-02-11 10:02 ` David Hildenbrand
2021-02-11 11:29 ` Mike Rapoport
2021-02-11 11:27 ` Mike Rapoport
2021-02-11 12:07 ` David Hildenbrand
2021-02-11 23:09 ` Mike Rapoport
2021-02-12 9:18 ` David Hildenbrand
2021-02-14 9:19 ` Mike Rapoport
2021-02-14 9:58 ` David Hildenbrand
2021-02-14 19:21 ` James Bottomley
2021-02-15 9:13 ` Michal Hocko
2021-02-15 18:14 ` James Bottomley
2021-02-15 19:20 ` Michal Hocko
2021-02-16 16:25 ` James Bottomley
2021-02-16 16:34 ` David Hildenbrand
2021-02-16 16:44 ` James Bottomley
2021-02-16 17:16 ` David Hildenbrand [this message]
2021-02-17 16:19 ` James Bottomley
2021-02-22 9:38 ` David Hildenbrand
2021-02-22 10:50 ` David Hildenbrand
2021-02-16 16:51 ` Michal Hocko
2021-02-11 11:20 ` Mike Rapoport
2021-02-11 12:30 ` Michal Hocko
2021-02-11 22:59 ` Mike Rapoport
2021-02-12 9:02 ` Michal Hocko
2021-02-08 8:49 ` [PATCH v17 08/10] PM: hibernate: disable when there are active secretmem users Mike Rapoport
2021-02-08 10:18 ` Michal Hocko
2021-02-08 10:32 ` David Hildenbrand
2021-02-08 10:51 ` Michal Hocko
2021-02-08 10:53 ` David Hildenbrand
2021-02-08 10:57 ` Michal Hocko
2021-02-08 11:13 ` David Hildenbrand
2021-02-08 11:14 ` David Hildenbrand
2021-02-08 11:26 ` David Hildenbrand
2021-02-08 12:17 ` Michal Hocko
2021-02-08 13:34 ` Michal Hocko
2021-02-08 13:40 ` David Hildenbrand
2021-02-08 21:28 ` Mike Rapoport
2021-02-22 7:34 ` Matthew Garrett
2021-02-22 10:23 ` Mike Rapoport
2021-02-22 18:27 ` Matthew Garrett
2021-02-22 19:17 ` Dan Williams
2021-02-22 19:21 ` James Bottomley
2021-02-08 8:49 ` [PATCH v17 09/10] arch, mm: wire up memfd_secret system call where relevant Mike Rapoport
2021-02-08 8:49 ` [PATCH v17 10/10] secretmem: test: add basic selftest for memfd_secret(2) Mike Rapoport
2021-02-08 9:27 ` [PATCH v17 00/10] mm: introduce memfd_secret system call to create "secret" memory areas David Hildenbrand
2021-02-08 21:13 ` Mike Rapoport
2021-02-08 21:38 ` David Hildenbrand
2021-02-09 8:59 ` Michal Hocko
2021-02-09 9:15 ` David Hildenbrand
2021-02-09 9:53 ` Michal Hocko
2021-02-09 10:23 ` David Hildenbrand
2021-02-09 10:30 ` David Hildenbrand
2021-02-09 13:25 ` Michal Hocko
2021-02-09 16:17 ` David Hildenbrand
2021-02-09 20:08 ` Michal Hocko
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