Re: [RFC]: mm,power: introduce MADV_WIPEONSUSPEND

Jann Horn
2020-07-03T13:29:53Z

On Fri, Jul 3, 2020 at 1:30 PM Michal Hocko <mhocko@kernel.org> wrote:
> On Fri 03-07-20 10:34:09, Catangiu, Adrian Costin wrote:
> > This patch adds logic to the kernel power code to zero out contents of
> > all MADV_WIPEONSUSPEND VMAs present in the system during its transition
> > to any suspend state equal or greater/deeper than Suspend-to-memory,
> > known as S3.
>
> How does the application learn that its memory got wiped? S2disk is an
> async operation and it can happen at any time during the task execution.
> So how does the application work to prevent from corrupted state - e.g.
> when suspended between two memory loads?

You can do it seqlock-style, kind of - you reserve the first byte of
the page or so as a "is this page initialized" marker, and after every
read from the page, you do a compiler barrier and check whether that
byte has been cleared.