linux-kernel - Re: [PATCH] Drivers: hv: vss: run only on supported host versions

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Message-ID: <87fv17xkfm.fsf@vitty.brq.redhat.com>
Date:	Mon, 19 Oct 2015 11:43:41 +0200
From:	Vitaly Kuznetsov <vkuznets@...hat.com>
To:	Olaf Hering <olaf@...fle.de>
Cc:	kys@...rosoft.com, haiyangz@...rosoft.com,
	gregkh@...uxfoundation.org, devel@...uxdriverproject.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Drivers: hv: vss: run only on supported host versions

Olaf Hering <olaf@...fle.de> writes:

> The Backup integration service on WS2012 has appearently trouble to
> negotiate with a guest which does not support the provided util version.
> Currently the VSS driver supports only version 5/0. A WS2012 offers only
> version 1/x and 3/x, and vmbus_prep_negotiate_resp correctly returns an
> empty icframe_vercnt/icmsg_vercnt. But the host ignores that and
> continues to send ICMSGTYPE_NEGOTIATE messages. The result are weird
> errors during boot and general misbehaviour.
>
> Check the Windows version to work around the host bug, skip hv_vss_init
> on WS2012 and older.
>
> Signed-off-by: Olaf Hering <olaf@...fle.de>
> ---
>  drivers/hv/hv_snapshot.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/drivers/hv/hv_snapshot.c b/drivers/hv/hv_snapshot.c
> index a548ae4..52f10ed 100644
> --- a/drivers/hv/hv_snapshot.c
> +++ b/drivers/hv/hv_snapshot.c
> @@ -331,6 +331,16 @@ static void vss_on_reset(void)
>  int
>  hv_vss_init(struct hv_util_service *srv)
>  {
> +	switch (vmbus_proto_version) {
> +		case VERSION_WS2008:
> +		case VERSION_WIN7:
> +		case VERSION_WIN8:

Wouldn't it be better to simplify it to
    if (vmbus_proto_version < VERSION_WIN8_1) {
        pr_warn();
        return ...
    }

E.g. there was a patch for storvsc some time ago:

commit 6ee5c61535a2df807069145970d3e7fa492a3fac
Author: Keith Mange <keith.mange@...rosoft.com>
Date:   Thu Aug 13 08:43:46 2015 -0700

    storvsc: Rather than look for sets of specific protocol versions,
    make decisions based on ranges.

> +			pr_warn("Integration service 'Backup (volume snapshot)'"
> +				" not supported on this host version.\n");
> +			return -ENOTSUPP;
> +		default:
> +			break;
> +	}
>  	recv_buffer = srv->recv_buffer;
>
>  	/*
> _______________________________________________
> devel mailing list
> devel@...uxdriverproject.org
> http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel

-- 
  Vitaly
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