linux-kernel - Re: [PATCH] KVM: x86: switch hugepage recovery thread to vhost

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

Message-ID: <Z2Scxe34IR5jRfdd@kbusch-mbp.dhcp.thefacebook.com>
Date: Thu, 19 Dec 2024 15:23:01 -0700
From: Keith Busch <kbusch@...nel.org>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	michael.christie@...cle.com, Tejun Heo <tj@...nel.org>,
	Luca Boccassi <bluca@...ian.org>
Subject: Re: [PATCH] KVM: x86: switch hugepage recovery thread to vhost_task

On Thu, Dec 19, 2024 at 09:30:16PM +0100, Paolo Bonzini wrote:
> On Thu, Dec 19, 2024 at 7:09 PM Keith Busch <kbusch@...nel.org> wrote:
> > > Is crosvm trying to do anything but exec?  If not, it should probably use the
> > > flag.
> >
> > Good point, and I'm not sure right now. I don't think I know any crosvm
> > developer experts but I'm working on that to get a better explanation of
> > what's happening,
> 
> Ok, I found the code and it doesn't exec (e.g.
> https://github.com/google/crosvm/blob/b339d3d7/src/crosvm/sys/linux/jail_warden.rs#L122),
> so that's not an option. 

Thanks, I was slowly getting there too. It's been a while since I had to
work with the languange, so I'm a bit rusty (no pun intended) at
navigating.

> Well, if I understand correctly from a
> cursory look at the code, crosvm is creating a jailed child process
> early, and then spawns further jails through it; so it's just this
> first process that has to cheat.
> 
> One possibility on the KVM side is to delay creating the vhost_task
> until the first KVM_RUN. I don't like it but...
> 
> I think we should nevertheless add something to the status file in
> procfs, that makes it easy to detect kernel tasks (PF_KTHREAD |
> PF_IO_WORKER | PF_USER_WORKER).

I currently think excluding kernel tasks from this check probably aligns
with what it's trying to do, so anything to make that easier is a good
step, IMO.