linux-kernel - Re: [PATCH] Xen/PCI: correct notifier used for device removal

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Message-ID: <56AF4911.8030208@citrix.com>
Date:	Mon, 1 Feb 2016 12:01:21 +0000
From:	David Vrabel <david.vrabel@...rix.com>
To:	Jan Beulich <JBeulich@...e.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	xen-devel <xen-devel@...ts.xenproject.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Xen/PCI: correct notifier used for device removal

On 01/02/16 11:58, Jan Beulich wrote:
> Commit 599bad38cf added BUS_NOTIFY_REMOVED_DEVICE in order to allow
> avoiding removal of IOMMU mappings before the driver actually got
> unbound from the device. Naturally we should be using this too.

Because otherwise...?  What happens if we don't make this change?

Removing IOMMU mappings for a device when the driver is still bound to
the device looks wrong to me. Surely the device is still active and may
still be performing DMA at this point?

David

> --- 4.5-rc2/drivers/xen/pci.c
> +++ 4.5-rc2-xen-PCI-remove-notifier/drivers/xen/pci.c
> @@ -185,7 +185,7 @@ static int xen_pci_notifier(struct notif
>  	case BUS_NOTIFY_ADD_DEVICE:
>  		r = xen_add_device(dev);
>  		break;
> -	case BUS_NOTIFY_DEL_DEVICE:
> +	case BUS_NOTIFY_REMOVED_DEVICE:
>  		r = xen_remove_device(dev);
>  		break;
>  	default:
> 
> 
>