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Date: Tue, 05 May 2020 23:50:33 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: paulmck@...nel.org
Cc: LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
Andy Lutomirski <luto@...nel.org>,
Alexandre Chartre <alexandre.chartre@...cle.com>,
Frederic Weisbecker <frederic@...nel.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Sean Christopherson <sean.j.christopherson@...el.com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Petr Mladek <pmladek@...e.com>,
Steven Rostedt <rostedt@...dmis.org>,
Joel Fernandes <joel@...lfernandes.org>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Juergen Gross <jgross@...e.com>,
Brian Gerst <brgerst@...il.com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Will Deacon <will@...nel.org>
Subject: Re: [patch V4 part 1 12/36] x86/kvm: Sanitize kvm_async_pf_task_wait()
"Paul E. McKenney" <paulmck@...nel.org> writes:
> On Tue, May 05, 2020 at 03:16:14PM +0200, Thomas Gleixner wrote:
>> RCU is watching for:
>>
>> #1 The vCPU exited and current is definitely not the idle task
>>
>> #2a The #PF entry code on the guest went through enter_from_user_mode()
>> which reactivates RCU
>
> I have to double-check... The NO_HZ_FULL case transitioning to/from
> userspace is entirely non-preemptible, correct? (After rcu_user_enter()
> and before rcu_user_exit(), respectively.)
Yes. It runs with interrupts disabled down to the actual return (sysret,
iret).
Thanks,
tglx
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