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From: Mike Rapoport <rppt@kernel.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andy Lutomirski <luto@kernel.org>, 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>, Idan Yaniv <idan.yaniv@ibm.com>,
	Ingo Molnar <mingo@redhat.com>,
	James Bottomley <jejb@linux.ibm.com>,
	"Kirill A. Shutemov" <kirill@shutemov.name>,
	Matthew Wilcox <willy@infradead.org>,
	Mike Rapoport <rppt@linux.ibm.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Tycho Andersen <tycho@tycho.ws>, Will Deacon <will@kernel.org>,
	Linux API <linux-api@vger.kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>,
	linux-nvdimm@lists.01.org,
	linux-riscv <linux-riscv@lists.infradead.org>,
	the arch/x86 maintainers <x86@kernel.org>,
	linaro-mm-sig@lists.linaro.org,
	Sumit Semwal <sumit.semwal@linaro.org>
Subject: Re: [PATCH 3/6] mm: introduce secretmemfd system call to create "secret" memory areas
Date: Mon, 20 Jul 2020 17:20:53 +0300	[thread overview]
Message-ID: <20200720142053.GC8593@kernel.org> (raw)
In-Reply-To: <CAK8P3a0NyvRMqH7X0YNO5E6DGtvZXD5ZcD6Y6n7AkocufkMnHA@mail.gmail.com>

On Mon, Jul 20, 2020 at 01:30:13PM +0200, Arnd Bergmann wrote:
> On Mon, Jul 20, 2020 at 11:25 AM Mike Rapoport <rppt@kernel.org> wrote:
> >
> > From: Mike Rapoport <rppt@linux.ibm.com>
> >
> > Introduce "secretmemfd" system call with the ability to create memory areas
> > visible only in the context of the owning process and not mapped not only
> > to other processes but in the kernel page tables as well.
> >
> > The user will create a file descriptor using the secretmemfd system call
> > where flags supplied as a parameter to this system call will define the
> > desired protection mode for the memory associated with that file
> > descriptor. Currently there are two protection modes:
> >
> > * exclusive - the memory area is unmapped from the kernel direct map and it
> >               is present only in the page tables of the owning mm.
> > * uncached  - the memory area is present only in the page tables of the
> >               owning mm and it is mapped there as uncached.
> >
> > For instance, the following example will create an uncached mapping (error
> > handling is omitted):
> >
> >         fd = secretmemfd(SECRETMEM_UNCACHED);
> >         ftruncate(fd, MAP_SIZE);
> >         ptr = mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED,
> >                    fd, 0);
> >
> > Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
> 
> I wonder if this should be more closely related to dmabuf file
> descriptors, which
> are already used for a similar purpose: sharing access to secret memory areas
> that are not visible to the OS but can be shared with hardware through device
> drivers that can import a dmabuf file descriptor.

TBH, I didn't think about dmabuf, but my undestanding is that is this
case memory areas are not visible to the OS because they are on device
memory rather than normal RAM and when dmabuf is backed by the normal
RAM, the memory is visible to the OS.

Did I miss anything?


>       Arnd

-- 
Sincerely yours,
Mike.

  reply	other threads:[~2020-07-20 14:21 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-20  9:24 [PATCH 0/6] " Mike Rapoport
2020-07-20  9:24 ` [PATCH 1/6] mm: add definition of PMD_PAGE_ORDER Mike Rapoport
2020-07-20  9:24 ` [PATCH 2/6] mmap: make mlock_future_check() global Mike Rapoport
2020-07-20  9:24 ` [PATCH 3/6] mm: introduce secretmemfd system call to create "secret" memory areas Mike Rapoport
2020-07-20 11:30   ` Arnd Bergmann
2020-07-20 14:20     ` Mike Rapoport [this message]
2020-07-20 14:34       ` Arnd Bergmann
2020-07-20 17:46         ` Mike Rapoport
2020-07-20 15:51     ` James Bottomley
2020-07-20 18:08       ` Arnd Bergmann
2020-07-20 19:16         ` James Bottomley
2020-07-20 20:05           ` Arnd Bergmann
2020-07-21 10:59   ` Michael Kerrisk (man-pages)
2020-07-20  9:24 ` [PATCH 4/6] arch, mm: wire up secretmemfd system call were relevant Mike Rapoport
2020-07-26 17:44   ` Palmer Dabbelt
2020-07-20  9:24 ` [PATCH 5/6] mm: secretmem: use PMD-size pages to amortize direct map fragmentation Mike Rapoport
2020-07-20  9:24 ` [PATCH 6/6] mm: secretmem: add ability to reserve memory at boot Mike Rapoport

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