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From: Anthony Yznaga <anthony.yznaga@oracle.com>
To: Kirill Tkhai <ktkhai@virtuozzo.com>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-mm@kvack.org, linux-arch@vger.kernel.org
Cc: 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, ebiederm@xmission.com, keescook@chromium.org,
	gerg@linux-m68k.org, christian.brauner@ubuntu.com,
	peterz@infradead.org, esyr@redhat.com, jgg@ziepe.ca,
	christian@kellner.me, areber@redhat.com, cyphar@cyphar.com,
	steven.sistare@oracle.com
Subject: Re: [RFC PATCH 0/5] madvise MADV_DOEXEC
Date: Tue, 28 Jul 2020 10:28:07 -0700
Message-ID: <e6699d15-8c86-8f9a-b840-7c3872e3ec8c@oracle.com> (raw)
In-Reply-To: <46891e3b-ca08-197d-935f-fa0a52a60051@virtuozzo.com>



On 7/28/20 4:34 AM, Kirill Tkhai wrote:
> On 27.07.2020 20:11, Anthony Yznaga wrote:
>> 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,
> So, the goal is an update of QEMU binary without a stopping of virtual machine?
Essentially, yes.  The VM is paused very briefly.

Anthony
>
>> 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.
>>
>> Patches 1 and 2 ensure that loading of ELF load segments does not silently
>> clobber existing VMAS, and remove assumptions that the stack is the only
>> VMA in the mm when the stack is set up.  Patch 1 re-introduces the use of
>> MAP_FIXED_NOREPLACE to load ELF binaries that addresses the previous issues
>> and could be considered on its own.
>>
>> Patches 3, 4, and 5 introduce the feature and an opt-in method for its use
>> using an ELF note.
>>
>> Anthony Yznaga (5):
>>   elf: reintroduce using MAP_FIXED_NOREPLACE for elf executable mappings
>>   mm: do not assume only the stack vma exists in setup_arg_pages()
>>   mm: introduce VM_EXEC_KEEP
>>   exec, elf: require opt-in for accepting preserved mem
>>   mm: introduce MADV_DOEXEC
>>
>>  arch/x86/Kconfig                       |   1 +
>>  fs/binfmt_elf.c                        | 196 +++++++++++++++++++++++++--------
>>  fs/exec.c                              |  33 +++++-
>>  include/linux/binfmts.h                |   7 +-
>>  include/linux/mm.h                     |   5 +
>>  include/uapi/asm-generic/mman-common.h |   3 +
>>  kernel/fork.c                          |   2 +-
>>  mm/madvise.c                           |  25 +++++
>>  mm/mmap.c                              |  47 ++++++++
>>  9 files changed, 266 insertions(+), 53 deletions(-)
>>



  reply index

Thread overview: 44+ 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
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 [this message]
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
2020-07-31 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
     [not found]                     ` <9371b8272fd84280ae40b409b260bab3@AcuMS.aculab.com>
2020-08-04 11:13                       ` Matthew Wilcox
2020-08-03 19:29                   ` Steven Sistare
2020-07-31 19:41 ` Steven Sistare

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