From: Sergey Senozhatsky <senozhatsky@chromium.org>
To: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Suleiman Souhlal <suleiman@google.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] x86/kvm: do not touch watchdogs in pvclock
Date: Sat, 17 Jul 2021 09:24:43 +0900 [thread overview]
Message-ID: <YPIjS2ZTksEkeiqK@google.com> (raw)
In-Reply-To: <20210716053405.1243239-1-senozhatsky@chromium.org>
On (21/07/16 14:34), Sergey Senozhatsky wrote:
>
> <IRQ>
> apic_timer_interrupt()
> smp_apic_timer_interrupt()
> hrtimer_interrupt()
> _raw_spin_lock_irqsave()
> lock_acquire()
> __lock_acquire()
> sched_clock_cpu()
> sched_clock()
> kvm_sched_clock_read()
> kvm_clock_read()
> pvclock_clocksource_read()
> pvclock_touch_watchdogs()
>
> Since this is VM and VCPU resume path, jiffies still maybe
> be outdated here, which is often the case on my device.
> pvclock_clocksource_read() clears PVCLOCK_GUEST_STOPPED,
> touches watchdogs, but it uses stale jiffies: 4294740764
> (for example).
Hmm, on the other hand, there is probably nothing that guarantees
that the first watchdog hard IRQ we execute on a resuming VCPU is
going to see updated jiffies, it still can use stale jiffies.
prev parent reply other threads:[~2021-07-17 0:24 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-16 5:34 [RFC PATCH] x86/kvm: do not touch watchdogs in pvclock Sergey Senozhatsky
2021-07-17 0:24 ` Sergey Senozhatsky [this message]
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