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From:   "Michael Kelley (LINUX)" <mikelley@microsoft.com>
To:     "Andrea Parri (Microsoft)" <parri.andrea@gmail.com>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
        Wei Hu <weh@microsoft.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Rob Herring <robh@kernel.org>,
        Krzysztof Wilczynski <kw@linux.com>,
        Bjorn Helgaas <bhelgaas@google.com>
CC:     "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [RFC PATCH 1/4] Drivers: hv: vmbus: Remove special code for
 unsolicited messages
Thread-Topic: [RFC PATCH 1/4] Drivers: hv: vmbus: Remove special code for
 unsolicited messages
Thread-Index: AQHYQrIn2sYSQ2mrxke3i7GPpdFhdKzZzOSg
Date:   Thu, 31 Mar 2022 18:00:53 +0000
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References: <20220328144244.100228-1-parri.andrea@gmail.com>
 <20220328144244.100228-2-parri.andrea@gmail.com>
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From: Andrea Parri (Microsoft) <parri.andrea@gmail.com> Sent: Monday, March=
 28, 2022 7:43 AM
>=20
> vmbus_requestor has included code for handling unsolicited messages
> since its introduction with commit e8b7db38449ac ("Drivers: hv: vmbus:
> Add vmbus_requestor data structure for VMBus hardening"); such code was
> motivated by the early use of vmbus_requestor from storvsc.  Since
> storvsc moved to a tag-based mechanism to generate/retrieve request IDs
> with commit bf5fd8cae3c8f ("scsi: storvsc: Use blk_mq_unique_tag() to
> generate requestIDs"), the special handling of unsolicited messages in
> vmbus_requestor is not useful and can be removed.
>=20
> Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
> ---
>  drivers/hv/channel.c | 13 +------------
>  1 file changed, 1 insertion(+), 12 deletions(-)
>=20
> diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
> index dc5c35210c16a..a253eee3aeb1a 100644
> --- a/drivers/hv/channel.c
> +++ b/drivers/hv/channel.c
> @@ -1243,11 +1243,7 @@ u64 vmbus_next_request_id(struct vmbus_channel
> *channel, u64 rqst_addr)
>=20
>  	spin_unlock_irqrestore(&rqstor->req_lock, flags);
>=20
> -	/*
> -	 * Cannot return an ID of 0, which is reserved for an unsolicited
> -	 * message from Hyper-V.
> -	 */
> -	return current_id + 1;
> +	return current_id;
>  }
>  EXPORT_SYMBOL_GPL(vmbus_next_request_id);
>=20
> @@ -1268,15 +1264,8 @@ u64 vmbus_request_addr(struct vmbus_channel *chann=
el,
> u64 trans_id)
>  	if (!channel->rqstor_size)
>  		return VMBUS_NO_RQSTOR;
>=20
> -	/* Hyper-V can send an unsolicited message with ID of 0 */
> -	if (!trans_id)
> -		return trans_id;
> -
>  	spin_lock_irqsave(&rqstor->req_lock, flags);
>=20
> -	/* Data corresponding to trans_id is stored at trans_id - 1 */
> -	trans_id--;
> -
>  	/* Invalid trans_id */
>  	if (trans_id >=3D rqstor->size || !test_bit(trans_id, rqstor->req_bitma=
p)) {
>  		spin_unlock_irqrestore(&rqstor->req_lock, flags);
> --
> 2.25.1

Reviewed-by: Michael Kelley <mikelley@microsoft.com>