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From: Mike Rapoport <rppt@kernel.org>
To: David Hildenbrand <david@redhat.com>
Cc: 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>,
	Hagen Paul Pfeifer <hagen@jauu.net>,
	Ingo Molnar <mingo@redhat.com>,
	James Bottomley <jejb@linux.ibm.com>,
	Kees Cook <keescook@chromium.org>,
	"Kirill A. Shutemov" <kirill@shutemov.name>,
	Matthew Wilcox <willy@infradead.org>,
	Matthew Garrett <mjg59@srcf.ucam.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Michal Hocko <mhocko@suse.com>,
	Mike Rapoport <rppt@linux.ibm.com>,
	Michael Kerrisk <mtk.manpages@gmail.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Palmer Dabbelt <palmerdabbelt@google.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Peter Zijlstra <peterz@infradead.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	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>,
	Yury Norov <yury.norov@gmail.com>,
	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
Subject: Re: [PATCH v19 5/8] mm: introduce memfd_secret system call to create "secret" memory areas
Date: Mon, 17 May 2021 10:23:09 +0300	[thread overview]
Message-ID: <YKIZ3Zfai00A2O15@kernel.org> (raw)
In-Reply-To: <ea1ddcfa-f52d-9a7d-cb7b-8502b38a90da@redhat.com>

On Fri, May 14, 2021 at 10:50:55AM +0200, David Hildenbrand wrote:
> On 13.05.21 20:47, Mike Rapoport wrote:
> > From: Mike Rapoport <rppt@linux.ibm.com>
> > 
> > Removing of the pages from the direct map may cause its fragmentation
> > on architectures that use large pages to map the physical memory
> > which affects the system performance. However, the original Kconfig
> > text for CONFIG_DIRECT_GBPAGES said that gigabyte pages in the direct
> > map "... can improve the kernel's performance a tiny bit ..." (commit
> > 00d1c5e05736 ("x86: add gbpages switches")) and the recent report [1]
> > showed that "... although 1G mappings are a good default choice,
> > there is no compelling evidence that it must be the only choice".
> > Hence, it is sufficient to have secretmem disabled by default with
> > the ability of a system administrator to enable it at boot time.
> 
> Maybe add a link to the Intel performance evaluation.
 
" ... the recent report [1]" and the link below.
 
> > Pages in the secretmem regions are unevictable and unmovable to
> > avoid accidental exposure of the sensitive data via swap or during
> > page migration.
 
...

> > A page that was a part of the secret memory area is cleared when it
> > is freed to ensure the data is not exposed to the next user of that
> > page.
> 
> You could skip that with init_on_free (and eventually also with
> init_on_alloc) set to avoid double clearing.

Right, but for now I'd prefer to keep this explicit in the secretmem
implementation. We may add the check for init_on_free/init_on_alloc later
on.


> > [1]
> > https://lore.kernel.org/linux-mm/213b4567-46ce-f116-9cdf-bbd0c884eb3c@linux.intel.com/
> 

-- 
Sincerely yours,
Mike.

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  reply	other threads:[~2021-05-17  7:26 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-13 18:47 [PATCH v19 0/8] mm: introduce memfd_secret system call to create "secret" memory areas Mike Rapoport
2021-05-13 18:47 ` [PATCH v19 1/8] mmap: make mlock_future_check() global Mike Rapoport
2021-05-14  8:27   ` David Hildenbrand
2021-05-13 18:47 ` [PATCH v19 2/8] riscv/Kconfig: make direct map manipulation options depend on MMU Mike Rapoport
2021-05-14  8:28   ` David Hildenbrand
2021-05-13 18:47 ` [PATCH v19 3/8] set_memory: allow set_direct_map_*_noflush() for multiple pages Mike Rapoport
2021-05-14  8:43   ` David Hildenbrand
2021-05-16  7:13     ` Mike Rapoport
2021-05-13 18:47 ` [PATCH v19 4/8] set_memory: allow querying whether set_direct_map_*() is actually enabled Mike Rapoport
2021-05-13 18:47 ` [PATCH v19 5/8] mm: introduce memfd_secret system call to create "secret" memory areas Mike Rapoport
2021-05-14  8:50   ` David Hildenbrand
2021-05-17  7:23     ` Mike Rapoport [this message]
2021-05-14  9:25   ` David Hildenbrand
2021-05-16  7:29     ` Mike Rapoport
2021-05-18  9:59       ` Michal Hocko
2021-05-18 10:06         ` David Hildenbrand
2021-05-18 10:31           ` Michal Hocko
2021-05-18 10:35             ` David Hildenbrand
2021-05-18 11:08               ` Michal Hocko
2021-05-19  7:13                 ` Mike Rapoport
2021-05-13 18:47 ` [PATCH v19 6/8] PM: hibernate: disable when there are active secretmem users Mike Rapoport
2021-05-14  9:27   ` David Hildenbrand
2021-05-18 10:24   ` Mark Rutland
2021-05-18 10:27     ` David Hildenbrand
2021-05-19  1:32     ` James Bottomley
2021-05-19  1:49       ` Dan Williams
2021-05-19  3:50         ` James Bottomley
2021-05-13 18:47 ` [PATCH v19 7/8] arch, mm: wire up memfd_secret system call where relevant Mike Rapoport
2021-05-14  9:27   ` David Hildenbrand
2021-05-13 18:47 ` [PATCH v19 8/8] secretmem: test: add basic selftest for memfd_secret(2) Mike Rapoport
2021-05-14  9:40   ` David Hildenbrand
2021-05-13 19:08 ` [PATCH v19 0/8] mm: introduce memfd_secret system call to create "secret" memory areas James Bottomley

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