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

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Message-ID: <rl5s5eykuzs4dgp23vpbagb4lntyl3uptwh54jzjjgfydynqvx@6xbbcjvb7zpn>
Date: Fri, 15 Nov 2024 17:59:07 +0100
From: Michal Koutný <mkoutny@...e.com>
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 Fri, Nov 08, 2024 at 08:07:37AM GMT, Paolo Bonzini <pbonzini@...hat.com> wrote:
> Since the worker kthread is tied to a user process, it's better if
> it behaves similarly to user tasks as much as possible, including
> being able to send SIGSTOP and SIGCONT.

Do you mean s/send/receive/?

Consequently, it's OK if a (possibly unprivileged) user stops this
thread forever (they only harm themselves, not the rest of the system),
correct?


> In fact, vhost_task is all that kvm_vm_create_worker_thread() wanted
> to be and more: not only it inherits the userspace process's cgroups,
> it has other niceties like being parented properly in the process
> tree.  Use it instead of the homegrown alternative.

It is nice indeed.
I think the bugs we saw are not so serious to warrant
Fixes: c57c80467f90e ("kvm: Add helper function for creating VM worker threads")
.
(But I'm posting it here so that I can find the reference later.)

Thanks,
Michal

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