netdev - Re: Bug inkvm_set

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Date:	Wed, 09 Mar 2011 13:28:43 +0100
From:	Jean-Philippe Menil <jean-philippe.menil@...v-nantes.fr>
To:	"Michael S. Tsirkin" <mst@...hat.com>
CC:	netdev@...r.kernel.org, kvm@...r.kernel.org,
	virtualization@...ts.linux-foundation.org
Subject: Re: Bug inkvm_set_irq

Le 08/03/2011 12:13, Michael S. Tsirkin a écrit :
> On Fri, Mar 04, 2011 at 10:39:05AM +0100, Jean-Philippe Menil wrote:
>> Yes, it's a 2.6.37.2 kernel.
> OK, here's a debugging patch.
> Please run with slab debugging as previously until you see
> 'eventfd bug detected!' in dmesg or until there is a crash.
> It might be also useful to enable timestampts on printk with
>   Symbol: PRINTK_TIME [=y]
>    │ Type  : boolean
>    │ Prompt: Show timing information on printks
>
> once you see the error, please upload the
> full dmesg output somewhere to we can track what
> goes on.
>
> Hopefully there won't be an oops this time which
> should make it easier for you to test (no need to
> reboot).
>
>
> diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
> index c1f1e3c..3cb679b 100644
> --- a/virt/kvm/eventfd.c
> +++ b/virt/kvm/eventfd.c
> @@ -32,6 +32,7 @@
>   #include<linux/eventfd.h>
>   #include<linux/kernel.h>
>   #include<linux/slab.h>
> +#include<linux/nmi.h>
>
>   #include "iodev.h"
>
> @@ -43,6 +44,8 @@
>    * --------------------------------------------------------------------
>    */
>
> +#define KVM_BAD_PTR ((void*)(long)(0x6b6b6b6b6b6b6b6bull))
> +
>   struct _irqfd {
>   	struct kvm               *kvm;
>   	struct eventfd_ctx       *eventfd;
> @@ -61,6 +64,13 @@ irqfd_inject(struct work_struct *work)
>   {
>   	struct _irqfd *irqfd = container_of(work, struct _irqfd, inject);
>   	struct kvm *kvm = irqfd->kvm;
> +	if (kvm == KVM_BAD_PTR) {
> +		printk(KERN_ERR "Eventfd bug detected!\n");
> +		printk(KERN_ERR "%s(work=%p,irqfd=%p,kvm=%p,gsi=%d)\n", __func__,
> +			work, irqfd, kvm, irqfd->gsi);
> +		trigger_all_cpu_backtrace();
> +		return;
> +	}
>
>   	kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1);
>   	kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0);
> @@ -75,6 +85,8 @@ irqfd_shutdown(struct work_struct *work)
>   	struct _irqfd *irqfd = container_of(work, struct _irqfd, shutdown);
>   	u64 cnt;
>
> +	printk(KERN_ERR "%s(work=%p,irqfd=%p,kvm=%p, gsi=%d)\n", __func__,
> +	       work, irqfd, irqfd->kvm, irqfd->gsi);
>   	/*
>   	 * Synchronize with the wait-queue and unhook ourselves to prevent
>   	 * further events.
> @@ -91,6 +103,8 @@ irqfd_shutdown(struct work_struct *work)
>   	 * It is now safe to release the object's resources
>   	 */
>   	eventfd_ctx_put(irqfd->eventfd);
> +	printk(KERN_ERR "kfree at %s(work=%p,irqfd=%p)\n", __func__,
> +	       work, irqfd);
>   	kfree(irqfd);
>   }
>
> @@ -111,6 +125,8 @@ static void
>   irqfd_deactivate(struct _irqfd *irqfd)
>   {
>   	BUG_ON(!irqfd_is_active(irqfd));
> +	printk(KERN_ERR "%s(irqfd=%p,kvm=%p, gsi=%d)\n", __func__,
> +	       irqfd, irqfd->kvm, irqfd->gsi);
>
>   	list_del_init(&irqfd->list);
>
> @@ -178,6 +194,8 @@ kvm_irqfd_assign(struct kvm *kvm, int fd, int gsi)
>
>   	irqfd->kvm = kvm;
>   	irqfd->gsi = gsi;
> +	printk(KERN_ERR "%s(irqfd=%p,kvm=%p, gsi=%d)\n", __func__,
> +	       irqfd, kvm, gsi);
>   	INIT_LIST_HEAD(&irqfd->list);
>   	INIT_WORK(&irqfd->inject, irqfd_inject);
>   	INIT_WORK(&irqfd->shutdown, irqfd_shutdown);
> @@ -264,6 +282,8 @@ kvm_irqfd_deassign(struct kvm *kvm, int fd, int gsi)
>   	struct _irqfd *irqfd, *tmp;
>   	struct eventfd_ctx *eventfd;
>
> +	printk(KERN_ERR "%s(kvm=%p, gsi=%d)\n", __func__,
> +	       kvm, gsi);
>   	eventfd = eventfd_ctx_fdget(fd);
>   	if (IS_ERR(eventfd))
>   		return PTR_ERR(eventfd);
> @@ -305,6 +325,7 @@ void
>   kvm_irqfd_release(struct kvm *kvm)
>   {
>   	struct _irqfd *irqfd, *tmp;
> +	printk(KERN_ERR "%s(kvm=%p)\n", __func__, kvm);
>
>   	spin_lock_irq(&kvm->irqfds.lock);
>
> --
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Hi,

I boot the host with the patched kernel yesterday.
No crach until now, but two "Eventfd bug detected!" in the log at "Mar  
9 02:04:31" and "Mar  9 02:15:17"
You can find part of the log at the following adress:
http://filex.univ-nantes.fr/get?k=jL4Fe7yfSMN57toAH7V

It a split file of the kern.log (1,4G), so if you need another part of 
the log, let me know.

Thanks for all.

Regards.


-- 
Jean-Philippe Menil - Pôle réseau Service IRTS
DSI Université de Nantes
jean-philippe.menil@...v-nantes.fr
Tel : 02.53.48.49.27 - Fax : 02.53.48.49.09

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