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From: Christian Brauner <christian.brauner@ubuntu.com>
To: Steven Sistare <steven.sistare@oracle.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
	Anthony Yznaga <anthony.yznaga@oracle.com>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-mm@kvack.org, linux-arch@vger.kernel.org,
	mhocko@kernel.org, tglx@linutronix.de, mingo@redhat.com,
	bp@alien8.de, x86@kernel.org, hpa@zytor.com,
	viro@zeniv.linux.org.uk, akpm@linux-foundation.org,
	arnd@arndb.de, keescook@chromium.org, gerg@linux-m68k.org,
	ktkhai@virtuozzo.com, peterz@infradead.org, esyr@redhat.com,
	jgg@ziepe.ca, christian@kellner.me, areber@redhat.com,
	cyphar@cyphar.com, linux-api@vger.kernel.org
Subject: Re: [RFC PATCH 0/5] madvise MADV_DOEXEC
Date: Tue, 28 Jul 2020 15:40:15 +0200	[thread overview]
Message-ID: <20200728134015.tmjy5hy4xden2v5h@wittgenstein> (raw)
In-Reply-To: <28125570-4129-bcba-099b-f90481cfbfe8@oracle.com>

On Mon, Jul 27, 2020 at 02:00:17PM -0400, Steven Sistare wrote:
> On 7/27/2020 1:07 PM, ebiederm@xmission.com wrote:
> > Anthony Yznaga <anthony.yznaga@oracle.com> writes:
> > 
> >> This patchset adds support for preserving an anonymous memory range across
> >> exec(3) using a new madvise MADV_DOEXEC argument.  The primary benefit for
> >> sharing memory in this manner, as opposed to re-attaching to a named shared
> >> memory segment, is to ensure it is mapped at the same virtual address in
> >> the new process as it was in the old one.  An intended use for this is to
> >> preserve guest memory for guests using vfio while qemu exec's an updated
> >> version of itself.  By ensuring the memory is preserved at a fixed address,
> >> vfio mappings and their associated kernel data structures can remain valid.
> >> In addition, for the qemu use case, qemu instances that back guest RAM with
> >> anonymous memory can be updated.
> > 
> > What is wrong with using a file descriptor to a possibly deleted file
> > and re-mmaping it?
> > 
> > There is already MAP_FIXED that allows you to ensure you have the same
> > address.
> 
> MAP_FIXED blows away any existing mapping in that range, which is not the 
> desired behavior.  We want to preserve the previously created mapping at

There's also MAP_FIXED_NOREPLACE since v4.17 in case that helps.

Note that this should really go to linux-api too. I won't argue to
resend it since that would mean spamming everyone's inbox with the same
thread again but in case you send a revised version, please ensure to Cc
linux-api. The glibc folks are listening on there too.

Thanks!
Christian

  reply	other threads:[~2020-07-28 13:40 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-27 17:11 Anthony Yznaga
2020-07-27 17:07 ` Eric W. Biederman
2020-07-27 18:00   ` Steven Sistare
2020-07-28 13:40     ` Christian Brauner [this message]
2020-07-27 17:11 ` [RFC PATCH 1/5] elf: reintroduce using MAP_FIXED_NOREPLACE for elf executable mappings Anthony Yznaga
2020-07-27 17:11 ` [RFC PATCH 2/5] mm: do not assume only the stack vma exists in setup_arg_pages() Anthony Yznaga
2020-07-27 17:11 ` [RFC PATCH 3/5] mm: introduce VM_EXEC_KEEP Anthony Yznaga
2020-07-28 13:38   ` Eric W. Biederman
2020-07-28 17:44     ` Anthony Yznaga
2020-07-29 13:52   ` Kirill A. Shutemov
2020-07-29 23:20     ` Anthony Yznaga
2020-07-27 17:11 ` [RFC PATCH 4/5] exec, elf: require opt-in for accepting preserved mem Anthony Yznaga
2020-07-27 17:11 ` [RFC PATCH 5/5] mm: introduce MADV_DOEXEC Anthony Yznaga
2020-07-28 13:22   ` Kirill Tkhai
2020-07-28 14:06     ` Steven Sistare
2020-07-28 11:34 ` [RFC PATCH 0/5] madvise MADV_DOEXEC Kirill Tkhai
2020-07-28 17:28   ` Anthony Yznaga
2020-07-28 14:23 ` Andy Lutomirski
2020-07-28 14:30   ` Steven Sistare
2020-07-30 15:22 ` Matthew Wilcox
2020-07-30 15:27   ` Christian Brauner
2020-07-30 15:34     ` Matthew Wilcox
2020-07-30 15:54       ` Christian Brauner
2020-07-31  9:12     ` Stefan Hajnoczi
2020-07-30 15:59   ` Steven Sistare
2020-07-30 17:12     ` Matthew Wilcox
2020-07-30 17:35       ` Steven Sistare
2020-07-30 17:49         ` Matthew Wilcox
2020-07-30 18:27           ` Steven Sistare
2020-07-30 21:58             ` Eric W. Biederman
2020-07-31 14:57               ` Steven Sistare
2020-07-31 15:27                 ` Matthew Wilcox
2020-07-31 16:11                   ` Steven Sistare
2020-07-31 16:56                     ` Jason Gunthorpe
2020-07-31 17:15                       ` Steven Sistare
2020-07-31 17:48                         ` Jason Gunthorpe
2020-07-31 17:55                           ` Steven Sistare
2020-08-03  8:32                             ` David Laight
2020-07-31 17:23                     ` Matthew Wilcox
2020-08-03 15:28                 ` Eric W. Biederman
2020-08-03 15:42                   ` James Bottomley
2020-08-03 20:03                     ` Steven Sistare
2020-08-04  8:44                     ` David Laight
2020-08-04 11:13                       ` Matthew Wilcox
2020-08-03 19:29                   ` Steven Sistare
2020-07-31 19:41 ` Steven Sistare
2021-07-08  9:52 ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2021-07-08 12:48   ` Steven Sistare

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