linux-kernel - Re: [PATCH v2 2/2] Drivers: hv: vmbus: Fix rescind handling in uio_hv

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Message-ID: <20240829134016.GA29554@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
Date: Thu, 29 Aug 2024 06:40:16 -0700
From: Saurabh Singh Sengar <ssengar@...ux.microsoft.com>
To: Naman Jain <namjain@...ux.microsoft.com>
Cc: "K . Y . Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Stephen Hemminger <stephen@...workplumber.org>,
	Michael Kelley <mhklinux@...look.com>, linux-hyperv@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2 2/2] Drivers: hv: vmbus: Fix rescind handling in
 uio_hv_generic

On Thu, Aug 29, 2024 at 12:43:12PM +0530, Naman Jain wrote:
> Rescind offer handling relies on rescind callbacks for some of the
> resources cleanup, if they are registered. It does not unregister
> vmbus device for the primary channel closure, when callback is
> registered. Without it, next onoffer does not come, rescind flag
> remains set and device goes to unusable state.
> 
> Add logic to unregister vmbus for the primary channel in rescind callback
> to ensure channel removal and relid release, and to ensure that next
> onoffer can be received and handled properly.
> 
> Cc: stable@...r.kernel.org
> Fixes: ca3cda6fcf1e ("uio_hv_generic: add rescind support")
> Signed-off-by: Naman Jain <namjain@...ux.microsoft.com>
> ---
>  drivers/hv/vmbus_drv.c       | 1 +
>  drivers/uio/uio_hv_generic.c | 8 ++++++++
>  2 files changed, 9 insertions(+)
> 
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 7242c4920427..c405295b930a 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -1980,6 +1980,7 @@ void vmbus_device_unregister(struct hv_device *device_obj)
>  	 */
>  	device_unregister(&device_obj->device);
>  }
> +EXPORT_SYMBOL_GPL(vmbus_device_unregister);
>  
>  #ifdef CONFIG_ACPI
>  /*
> diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
> index e3e66a3e85a8..870409599411 100644
> --- a/drivers/uio/uio_hv_generic.c
> +++ b/drivers/uio/uio_hv_generic.c
> @@ -121,6 +121,14 @@ static void hv_uio_rescind(struct vmbus_channel *channel)
>  
>  	/* Wake up reader */
>  	uio_event_notify(&pdata->info);
> +
> +	/*
> +	 * With rescind callback registered, rescind path will not unregister the device
> +	 * from vmbus when the primary channel is rescinded.
> +	 * Without it, rescind handling is incomplete and next onoffer msg does not come.
> +	 * Unregister the device from vmbus here.
> +	 */
> +	vmbus_device_unregister(channel->device_obj);
>  }
>  
>  /* Sysfs API to allow mmap of the ring buffers
> -- 
> 2.34.1
>

For the series,
Reviewed-by: Saurabh Sengar <ssengar@...ux.microsoft.com>