From: Nicolas Saenz Julienne <nsaenzju@redhat.com>
To: Mark Rutland <mark.rutland@arm.com>, maz <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>, paulmck <paulmck@kernel.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
rcu <rcu@vger.kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
frederic <frederic@kernel.org>,
kvmarm@lists.cs.columbia.edu,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Possible nohz-full/RCU issue in arm64 KVM
Date: Fri, 17 Dec 2021 12:51:57 +0100 [thread overview]
Message-ID: <d80e440375896f75d45e227d40af60ca7ba24ceb.camel@redhat.com> (raw)
Hi All,
arm64's guest entry code does the following:
int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
{
[...]
guest_enter_irqoff();
ret = kvm_call_hyp_ret(__kvm_vcpu_run, vcpu);
[...]
local_irq_enable();
/*
* We do local_irq_enable() before calling guest_exit() so
* that if a timer interrupt hits while running the guest we
* account that tick as being spent in the guest. We enable
* preemption after calling guest_exit() so that if we get
* preempted we make sure ticks after that is not counted as
* guest time.
*/
guest_exit();
[...]
}
On a nohz-full CPU, guest_{enter,exit}() delimit an RCU extended quiescent
state (EQS). Any interrupt happening between local_irq_enable() and
guest_exit() should disable that EQS. Now, AFAICT all el0 interrupt handlers do
the right thing if trggered in this context, but el1's won't. Is it possible to
hit an el1 handler (for example __el1_irq()) there?
Thanks,
--
Nicolás Sáenz
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next reply other threads:[~2021-12-17 11:53 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-17 11:51 Nicolas Saenz Julienne [this message]
2021-12-17 13:21 ` Possible nohz-full/RCU issue in arm64 KVM Mark Rutland
2021-12-17 14:15 ` Nicolas Saenz Julienne
2021-12-17 14:38 ` Mark Rutland
2021-12-17 15:54 ` Paolo Bonzini
2021-12-17 16:07 ` Paul E. McKenney
2021-12-17 16:20 ` Nicolas Saenz Julienne
2021-12-17 16:43 ` Paul E. McKenney
2021-12-17 16:34 ` Paolo Bonzini
2021-12-17 16:45 ` Paul E. McKenney
2021-12-17 17:02 ` Paolo Bonzini
2021-12-17 17:12 ` Paul E. McKenney
2021-12-17 17:23 ` Paolo Bonzini
2021-12-17 17:47 ` Paul E. McKenney
2022-01-04 16:39 ` Mark Rutland
2022-01-04 17:07 ` Paolo Bonzini
2022-01-11 11:32 ` Nicolas Saenz Julienne
2022-01-11 12:23 ` Mark Rutland
2021-12-17 14:51 ` Paolo Bonzini
2021-12-20 14:28 ` Marc Zyngier
2021-12-20 16:10 ` Frederic Weisbecker
2022-01-04 13:24 ` Mark Rutland
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