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Date: Fri, 31 Jul 2020 15:41:37 -0400 From: Steven Sistare <steven.sistare@...cle.com> To: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, linux-arch@...r.kernel.org Cc: mhocko@...nel.org, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com, viro@...iv.linux.org.uk, akpm@...ux-foundation.org, arnd@...db.de, ebiederm@...ssion.com, keescook@...omium.org, gerg@...ux-m68k.org, ktkhai@...tuozzo.com, christian.brauner@...ntu.com, peterz@...radead.org, esyr@...hat.com, jgg@...pe.ca, christian@...lner.me, areber@...hat.com, cyphar@...har.com Subject: Re: [RFC PATCH 0/5] madvise MADV_DOEXEC On 7/27/2020 1:11 PM, 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, > 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. I forgot to mention, our use case is not just theoretical. It has been implemented and is pretty cool (but I am biased). The pause time for the guest is in the 100 - 200 msec range. We submitted qemu patches for review based on the MADV_DOEXEC proposal. In case you are curious: https://lore.kernel.org/qemu-devel/1596122076-341293-1-git-send-email-steven.sistare@oracle.com/ - Steve
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