linux-kernel - Re: [PATCH] vfio/pci: Clear token on bypass registration failure

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Date:   Wed, 11 Nov 2020 10:15:04 +0800
From:   gchen chen <gchen.guomin@...il.com>
To:     Alex Williamson <alex.williamson@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        guomin_chen@...a.com
Subject: Re: [PATCH] vfio/pci: Clear token on bypass registration failure

Thanks a lot.

Alex Williamson <alex.williamson@...hat.com> 于2020年10月19日周一 下午9:30写道：
>
> The eventfd context is used as our irqbypass token, therefore if an
> eventfd is re-used, our token is the same.  The irqbypass code will
> return an -EBUSY in this case, but we'll still attempt to unregister
> the producer, where if that duplicate token still exists, results in
> removing the wrong object.  Clear the token of failed producers so
> that they harmlessly fall out when unregistered.
>
> Fixes: 6d7425f109d2 ("vfio: Register/unregister irq_bypass_producer")
> Reported-by: guomin chen <guomin_chen@...a.com>
> Tested-by: guomin chen <guomin_chen@...a.com>
> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> ---
>  drivers/vfio/pci/vfio_pci_intrs.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
> index 1d9fb2592945..869dce5f134d 100644
> --- a/drivers/vfio/pci/vfio_pci_intrs.c
> +++ b/drivers/vfio/pci/vfio_pci_intrs.c
> @@ -352,11 +352,13 @@ static int vfio_msi_set_vector_signal(struct vfio_pci_device *vdev,
>         vdev->ctx[vector].producer.token = trigger;
>         vdev->ctx[vector].producer.irq = irq;
>         ret = irq_bypass_register_producer(&vdev->ctx[vector].producer);
> -       if (unlikely(ret))
> +       if (unlikely(ret)) {
>                 dev_info(&pdev->dev,
>                 "irq bypass producer (token %p) registration fails: %d\n",
>                 vdev->ctx[vector].producer.token, ret);
>
> +               vdev->ctx[vector].producer.token = NULL;
> +       }
>         vdev->ctx[vector].trigger = trigger;
>
>         return 0;
>