From: Avi Kivity <avi@redhat.com>
To: Sheng Yang <sheng@linux.intel.com>
Cc: Amit Shah <amshah@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
kvm@vger.kernel.org, Amit Shah <amit.shah@redhat.com>,
"Han, Weidong" <weidong.han@intel.com>
Subject: Re: [PATCH 15/15] KVM: Fix racy in kvm_free_assigned_irq
Date: Mon, 29 Dec 2008 15:37:52 +0200 [thread overview]
Message-ID: <4958D2B0.6050904@redhat.com> (raw)
In-Reply-To: <200812292023.29565.sheng@linux.intel.com>
Sheng Yang wrote:
> The free assigned device in the destroy path of VM, so as free irq. And we got
> cancel_work_sync() in free irq which can sync with the execution of scheduled
> work. And now before cancel_work_sync(), we disable the interrupt so that no
> more schedule work happen again. So after cancel_work_sync(), everything(I
> think it's irq handler and schedule work here) asynchronously should quiet
> down.
>
> Or I miss something?
>
Suppose the work_struct gets scheduled, but is delayed somewhere in the
scheduler. Some kill -9s the VM, and it starts getting destroyed.
cancel_work_sync() can no longer truly cancel the work, so it has to
schedule and wait for its completion.
So now we have kvm_assigned_dev_interrupt_work_handler() running in a
partially destroyed VM. It may work or not, but it's a fragile
situation (changing the order of destruction of components will likely
break things) and it's easy to avoid by keeping the reference count
elevated.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
next prev parent reply other threads:[~2008-12-29 13:37 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-25 9:09 [PATCH 0/15] Device assignment & MSI enhancement Sheng Yang
2008-12-25 9:09 ` [PATCH 01/15] KVM: Add MSI_ACTION flag for assigned irq Sheng Yang
2008-12-25 9:09 ` [PATCH 02/15] KVM: Use kvm_free_assigned_irq() for free irq Sheng Yang
2008-12-25 9:09 ` [PATCH 03/15] KVM: Add support to disable MSI for assigned device Sheng Yang
2008-12-25 9:09 ` [PATCH 04/15] KVM: Add a route layer to convert MSI message to GSI Sheng Yang
2008-12-25 9:09 ` [PATCH 05/15] KVM: Using gsi_msg mapping for MSI device assignment Sheng Yang
2008-12-25 9:09 ` [PATCH 06/15] KVM: Improve MSI dispatch function Sheng Yang
2008-12-25 9:09 ` [PATCH 07/15] KVM: Using ioapic_irqchip() macro for kvm_set_irq Sheng Yang
2008-12-25 9:09 ` [PATCH 08/15] KVM: Merge MSI handling to kvm_set_irq Sheng Yang
2008-12-25 9:09 ` [PATCH 09/15] KVM: Split IOAPIC structure Sheng Yang
2008-12-25 9:09 ` [PATCH 10/15] KVM: Unified the delivery of IOAPIC and MSI Sheng Yang
2008-12-25 9:09 ` [PATCH 11/15] KVM: Change API of kvm_ioapic_get_delivery_bitmask Sheng Yang
2008-12-25 9:09 ` [PATCH 12/15] KVM: Update intr delivery func to accept unsigned long* bitmap Sheng Yang
2008-12-25 9:09 ` [PATCH 13/15] KVM: bit ops for deliver_bitmap Sheng Yang
2008-12-25 9:09 ` [PATCH 14/15] KVM: Using kfifo for irq recording Sheng Yang
2008-12-26 2:29 ` [PATCH 14/15] KVM: Replace host_irq_disable with a new flag Sheng Yang
2008-12-25 9:09 ` [PATCH 15/15] KVM: Fix racy in kvm_free_assigned_irq Sheng Yang
2008-12-25 11:56 ` Sheng Yang
2008-12-26 2:30 ` Sheng Yang
2008-12-27 20:06 ` Marcelo Tosatti
2008-12-27 20:15 ` Marcelo Tosatti
2008-12-28 11:24 ` Sheng Yang
2008-12-28 12:57 ` Avi Kivity
2008-12-29 5:42 ` Amit Shah
2008-12-29 12:23 ` Sheng Yang
2008-12-29 13:37 ` Avi Kivity [this message]
2008-12-29 13:49 ` Sheng Yang
2008-12-29 15:20 ` Marcelo Tosatti
2008-12-30 2:14 ` Sheng Yang
2008-12-30 16:45 ` Marcelo Tosatti
2008-12-31 5:43 ` Sheng Yang
2009-01-02 0:10 ` Marcelo Tosatti
2009-01-05 7:07 ` Sheng Yang
2009-01-05 13:27 ` Avi Kivity
2009-01-06 1:25 ` Sheng Yang
2008-12-29 13:20 ` Avi Kivity
2008-12-25 9:13 ` [PATCH 0/15] Device assignment & MSI enhancement Sheng Yang
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