linux-kernel - Re: "nosmt" breaks resuming from hibernation (was Re: [5.2-rc1 regression]: nvme vs. hibernation)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <nycvar.YFH.7.76.1905291118100.1962@cbobk.fhfr.pm>
Date:   Wed, 29 May 2019 11:20:40 +0200 (CEST)
From:   Jiri Kosina <jikos@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     Dongli Zhang <dongli.zhang@...cle.com>,
        Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...nel.dk>,
        Sagi Grimberg <sagi@...mberg.me>, linux-kernel@...r.kernel.org,
        linux-nvme@...ts.infradead.org,
        Keith Busch <keith.busch@...el.com>,
        Hannes Reinecke <hare@...e.de>, Christoph Hellwig <hch@....de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>, linux-pm@...r.kernel.org,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: "nosmt" breaks resuming from hibernation (was Re: [5.2-rc1
 regression]: nvme vs. hibernation)

On Wed, 29 May 2019, Peter Zijlstra wrote:

> > > I verified that it succesfully makes it to the point where restore_image()
> > > is called from swsusp_arch_resume() (and verified that only BSP is alive
> > > at that time), but the old kernel never comes back and triplefault-like
> > > reboot happens.
> 
> which means that even without nosmt all 'other' CPUs are offline. And
> when I look at resume_target_kernel() I see it call
> hibernate_resume_nonboot_cpu_disable().
> 
> So how is the SMT offline different from that offline? afaict they all 
> get into play_dead()->native_play_dead()->mwait_play_dead().

There is no way those other CPUs have been offlined before to the 
native_play_dead() state, as this is way before any userspace was alive to 
initiate any kind of hotplug.

So they are guaranteed to have been all online, and then offlined properly 
to resume_play_dead(). 'nosmt' is the only exception there, as it's the 
only kind of offlining that has already happened at this point.

Let's continue in the other thread.

Thanks,

-- 
Jiri Kosina
SUSE Labs