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From:   Long Li <longli@microsoft.com>
To:     Saurabh Sengar <ssengar@linux.microsoft.com>,
        Saurabh Singh Sengar <ssengar@microsoft.com>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        "wei.liu@kernel.org" <wei.liu@kernel.org>,
        Dexuan Cui <decui@microsoft.com>,
        "jejb@linux.ibm.com" <jejb@linux.ibm.com>,
        "martin.petersen@oracle.com" <martin.petersen@oracle.com>,
        "Michael Kelley (LINUX)" <mikelley@microsoft.com>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] scsi: storvsc: Removing Pre Win8 related logic
Thread-Topic: [PATCH] scsi: storvsc: Removing Pre Win8 related logic
Thread-Index: AQHYaVtu6iPdAKkK5kWzN5rtSKpgta0oKY5A
Date:   Fri, 20 May 2022 19:22:35 +0000
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References: <1652729430-12632-1-git-send-email-ssengar@linux.microsoft.com>
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> Subject: [PATCH] scsi: storvsc: Removing Pre Win8 related logic
>=20
> The latest storvsc code has already removed the support for windows 7 and
> earlier. There is still some code logic reamining which is there to suppo=
rt pre
> Windows 8 OS. This patch removes these stale logic.
> This patch majorly does three things :
>=20
> 1. Removes vmscsi_size_delta and its logic, as the vmscsi_request struct =
is same
> for all the OS post windows 8 there is no need of delta.
> 2. Simplify sense_buffer_size logic, as there is single buffer size for a=
ll the post
> windows 8 OS.
> 3. Embed the vmscsi_win8_extension structure inside the vmscsi_request, a=
s
> there is no separate handling required for different OS.
>=20
> Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
> ---
>  drivers/scsi/storvsc_drv.c | 135 +++++++++----------------------------
>  1 file changed, 33 insertions(+), 102 deletions(-)
>=20
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c inde=
x
> 5585e9d30bbf..1b7808e91f0b 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -137,18 +137,16 @@ struct hv_fc_wwn_packet {
>  #define STORVSC_MAX_CMD_LEN			0x10
>=20
>  #define POST_WIN7_STORVSC_SENSE_BUFFER_SIZE	0x14
> -#define PRE_WIN8_STORVSC_SENSE_BUFFER_SIZE	0x12
>=20
>  #define STORVSC_SENSE_BUFFER_SIZE		0x14
>  #define STORVSC_MAX_BUF_LEN_WITH_PADDING	0x14
>=20
>  /*
> - * Sense buffer size changed in win8; have a run-time
> - * variable to track the size we should use.  This value will
> - * likely change during protocol negotiation but it is valid
> - * to start by assuming pre-Win8.
> + * Sense buffer size was differnt pre win8 but those OS are not
> + supported any
> + * more starting 5.19 kernel. This results in to supporting a single
> + value from
> + * win8 onwards.
>   */
> -static int sense_buffer_size =3D PRE_WIN8_STORVSC_SENSE_BUFFER_SIZE;
> +static int sense_buffer_size =3D POST_WIN7_STORVSC_SENSE_BUFFER_SIZE;
>=20
>  /*
>   * The storage protocol version is determined during the
> @@ -177,18 +175,6 @@ do {
> 		\
>  		dev_warn(&(dev)->device, fmt, ##__VA_ARGS__);	\
>  } while (0)
>=20
> -struct vmscsi_win8_extension {
> -	/*
> -	 * The following were added in Windows 8
> -	 */
> -	u16 reserve;
> -	u8  queue_tag;
> -	u8  queue_action;
> -	u32 srb_flags;
> -	u32 time_out_value;
> -	u32 queue_sort_ey;
> -} __packed;
> -
>  struct vmscsi_request {
>  	u16 length;
>  	u8 srb_status;
> @@ -214,46 +200,23 @@ struct vmscsi_request {
>  	/*
>  	 * The following was added in win8.
>  	 */
> -	struct vmscsi_win8_extension win8_extension;
> +	u16 reserve;
> +	u8  queue_tag;
> +	u8  queue_action;
> +	u32 srb_flags;
> +	u32 time_out_value;
> +	u32 queue_sort_ey;
>=20
>  } __attribute((packed));
>=20
>  /*
> - * The list of storage protocols in order of preference.
> + * The list of windows version in order of preference.
>   */
> -struct vmstor_protocol {
> -	int protocol_version;
> -	int sense_buffer_size;
> -	int vmscsi_size_delta;
> -};
>=20
> -
> -static const struct vmstor_protocol vmstor_protocols[] =3D {
> -	{
> +static const int protocol_version[] =3D {
>  		VMSTOR_PROTO_VERSION_WIN10,
> -		POST_WIN7_STORVSC_SENSE_BUFFER_SIZE,
> -		0
> -	},
> -	{
>  		VMSTOR_PROTO_VERSION_WIN8_1,
> -		POST_WIN7_STORVSC_SENSE_BUFFER_SIZE,
> -		0
> -	},
> -	{
>  		VMSTOR_PROTO_VERSION_WIN8,
> -		POST_WIN7_STORVSC_SENSE_BUFFER_SIZE,
> -		0
> -	},
> -	{
> -		VMSTOR_PROTO_VERSION_WIN7,
> -		PRE_WIN8_STORVSC_SENSE_BUFFER_SIZE,
> -		sizeof(struct vmscsi_win8_extension),
> -	},
> -	{
> -		VMSTOR_PROTO_VERSION_WIN6,
> -		PRE_WIN8_STORVSC_SENSE_BUFFER_SIZE,
> -		sizeof(struct vmscsi_win8_extension),
> -	}
>  };
>=20
>=20
> @@ -409,9 +372,7 @@ static void storvsc_on_channel_callback(void *context=
);
>  #define STORVSC_IDE_MAX_CHANNELS			1
>=20
>  /*
> - * Upper bound on the size of a storvsc packet. vmscsi_size_delta is not
> - * included in the calculation because it is set after STORVSC_MAX_PKT_S=
IZE
> - * is used in storvsc_connect_to_vsp
> + * Upper bound on the size of a storvsc packet.
>   */
>  #define STORVSC_MAX_PKT_SIZE (sizeof(struct vmpacket_descriptor) +\
>  			      sizeof(struct vstor_packet))
> @@ -452,17 +413,6 @@ struct storvsc_device {
>  	unsigned char path_id;
>  	unsigned char target_id;
>=20
> -	/*
> -	 * The size of the vmscsi_request has changed in win8. The
> -	 * additional size is because of new elements added to the
> -	 * structure. These elements are valid only when we are talking
> -	 * to a win8 host.
> -	 * Track the correction to size we need to apply. This value
> -	 * will likely change during protocol negotiation but it is
> -	 * valid to start by assuming pre-Win8.
> -	 */
> -	int vmscsi_size_delta;
> -
>  	/*
>  	 * Max I/O, the device can support.
>  	 */
> @@ -795,8 +745,7 @@ static void  handle_multichannel_storage(struct
> hv_device *device, int max_chns)
>  	vstor_packet->sub_channel_count =3D num_sc;
>=20
>  	ret =3D vmbus_sendpacket(device->channel, vstor_packet,
> -			       (sizeof(struct vstor_packet) -
> -			       stor_device->vmscsi_size_delta),
> +			       sizeof(struct vstor_packet),
>  			       VMBUS_RQST_INIT,
>  			       VM_PKT_DATA_INBAND,
>=20
> VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
> @@ -864,8 +813,7 @@ static int storvsc_execute_vstor_op(struct hv_device
> *device,
>  	vstor_packet->flags =3D REQUEST_COMPLETION_FLAG;
>=20
>  	ret =3D vmbus_sendpacket(device->channel, vstor_packet,
> -			       (sizeof(struct vstor_packet) -
> -			       stor_device->vmscsi_size_delta),
> +			       sizeof(struct vstor_packet),
>  			       VMBUS_RQST_INIT,
>  			       VM_PKT_DATA_INBAND,
>=20
> VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
> @@ -915,14 +863,13 @@ static int storvsc_channel_init(struct hv_device
> *device, bool is_fc)
>  	 * Query host supported protocol version.
>  	 */
>=20
> -	for (i =3D 0; i < ARRAY_SIZE(vmstor_protocols); i++) {
> +	for (i =3D 0; i < ARRAY_SIZE(protocol_version); i++) {
>  		/* reuse the packet for version range supported */
>  		memset(vstor_packet, 0, sizeof(struct vstor_packet));
>  		vstor_packet->operation =3D
>  			VSTOR_OPERATION_QUERY_PROTOCOL_VERSION;
>=20
> -		vstor_packet->version.major_minor =3D
> -			vmstor_protocols[i].protocol_version;
> +		vstor_packet->version.major_minor =3D protocol_version[i];
>=20
>  		/*
>  		 * The revision number is only used in Windows; set it to 0.
> @@ -936,14 +883,7 @@ static int storvsc_channel_init(struct hv_device *de=
vice,
> bool is_fc)
>  			return -EINVAL;
>=20
>  		if (vstor_packet->status =3D=3D 0) {
> -			vmstor_proto_version =3D
> -				vmstor_protocols[i].protocol_version;
> -
> -			sense_buffer_size =3D
> -				vmstor_protocols[i].sense_buffer_size;
> -
> -			stor_device->vmscsi_size_delta =3D
> -				vmstor_protocols[i].vmscsi_size_delta;
> +			vmstor_proto_version =3D protocol_version[i];
>=20
>  			break;
>  		}

Now the code for querying versions will fail on earlier Hyper-V versions, u=
nlike the pre-patch code it will never fail.

Can you use a dev_err() to indicate this failure? This can help customers r=
unning into this and they will not call support.

Long