From: Marcelo Tosatti <mtosatti@redhat.com>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Avi Kivity <avi@redhat.com>, kvm-devel <kvm@vger.kernel.org>
Subject: Re: [PATCH v2 1/2] kvm: x86: Fix racy event propagation in kmv timer
Date: Tue, 9 Jun 2009 10:59:07 -0300 [thread overview]
Message-ID: <20090609135907.GA8016@amt.cnet> (raw)
In-Reply-To: <4A2E657D.5090405@siemens.com>
On Tue, Jun 09, 2009 at 03:37:01PM +0200, Jan Kiszka wrote:
> v2 as requested in private discussion: Broken into two pieces, and the
> second one will not change the original semantic.
>
> -------------->
>
> Minor issue that likely had no practical relevance: The kvm timer
> function so far incremented the pending counter and then may reset it
> again to 1 in case reinjection was disabled. This opened a small racy
> window with the corresponding VCPU loop that may have happened to run on
> another (real) CPU and already consumed the value.
>
> Fix it by skipping the incrementation in case pending is already > 0.
> This opens a different race windows, but may only rarely cause lost
> events in case we do not care about them anyway (!reinject).
>
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
ACK both, thanks.
next prev parent reply other threads:[~2009-06-09 13:59 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-09 9:28 [PATCH] kvm: x86: Fix racy event propagation in kmv timer Jan Kiszka
2009-06-09 13:37 ` [PATCH v2 1/2] " Jan Kiszka
2009-06-09 13:59 ` Marcelo Tosatti [this message]
2009-06-14 11:18 ` Avi Kivity
2009-06-09 13:37 ` [PATCH v2 2/2] kvm: x86: Drop useless atomic test from timer function Jan Kiszka
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