linux-kernel - Re: [Xen-devel][PATCH] Input: xen-kbdfront - signal the backend that we disconnect

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Date:   Fri, 22 Mar 2019 12:03:02 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Oleksandr Andrushchenko <andr2000@...il.com>,
        xen-devel@...ts.xenproject.org, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org, dmitry.torokhov@...il.com,
        boris.ostrovsky@...cle.com
Cc:     Volodymyr_Babchuk@...m.com,
        Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
Subject: Re: [Xen-devel][PATCH] Input: xen-kbdfront - signal the backend that
 we disconnect

On 15/03/2019 10:23, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
> 
> While disconnecting from the backend we clean up shared resources
> (event channel, ring buffer), but never let the backend know about
> that. This may lead to inconsistent backend state and/or shared
> resources use.
> Fix this by explicitly letting the backend know that frontend has
> destroyed shared resources by changing its Xen bus state accordingly.
> 
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
> ---
>  drivers/input/misc/xen-kbdfront.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/input/misc/xen-kbdfront.c b/drivers/input/misc/xen-kbdfront.c
> index 24bc5c5d876f..ecb6e719e0e2 100644
> --- a/drivers/input/misc/xen-kbdfront.c
> +++ b/drivers/input/misc/xen-kbdfront.c
> @@ -488,6 +488,8 @@ static int xenkbd_connect_backend(struct xenbus_device *dev,
>  
>  static void xenkbd_disconnect_backend(struct xenkbd_info *info)
>  {
> +	xenbus_switch_state(info->xbdev, XenbusStateClosing);
> +
>  	if (info->irq >= 0)
>  		unbind_from_irqhandler(info->irq, info);
>  	info->irq = -1;
> 

As already stated for the related netfront patch: I'm not sure this
is really what we want. Have you tested xl save/restore or migration
of the guest with your patch applied?


Juergen