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Date:   Fri, 20 May 2022 16:07:42 +0000
From:   Wei Liu <wei.liu@kernel.org>
To:     Saurabh Sengar <ssengar@linux.microsoft.com>
Cc:     ssengar@microsoft.com, kys@microsoft.com, haiyangz@microsoft.com,
        sthemmin@microsoft.com, wei.liu@kernel.org, decui@microsoft.com,
        jejb@linux.ibm.com, martin.petersen@oracle.com,
        mikelley@microsoft.com, linux-hyperv@vger.kernel.org,
        linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org,
        longli@microsoft.com
Subject: Re: [PATCH] scsi: storvsc: Removing Pre Win8 related logic
Message-ID: <20220520160742.jfrfzep6nsswwxxj@liuwe-devbox-debian-v2>
References: <1652729430-12632-1-git-send-email-ssengar@linux.microsoft.com>
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CC Long Li

On Mon, May 16, 2022 at 12:30:30PM -0700, Saurabh Sengar wrote:
> 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 support
> pre Windows 8 OS. This patch removes these stale logic.
> This patch majorly does three things :
> 
> 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
> all the post windows 8 OS.
> 3. Embed the vmscsi_win8_extension structure inside the vmscsi_request,
> as there is no separate handling required for different OS.
> 
> Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
> ---
>  drivers/scsi/storvsc_drv.c | 135 +++++++++----------------------------
>  1 file changed, 33 insertions(+), 102 deletions(-)
> 
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> index 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
>  
>  #define POST_WIN7_STORVSC_SENSE_BUFFER_SIZE	0x14
> -#define PRE_WIN8_STORVSC_SENSE_BUFFER_SIZE	0x12
>  
>  #define STORVSC_SENSE_BUFFER_SIZE		0x14
>  #define STORVSC_MAX_BUF_LEN_WITH_PADDING	0x14
>  
>  /*
> - * 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 = PRE_WIN8_STORVSC_SENSE_BUFFER_SIZE;
> +static int sense_buffer_size = POST_WIN7_STORVSC_SENSE_BUFFER_SIZE;
>  
>  /*
>   * The storage protocol version is determined during the
> @@ -177,18 +175,6 @@ do {								\
>  		dev_warn(&(dev)->device, fmt, ##__VA_ARGS__);	\
>  } while (0)
>  
> -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;
>  
>  } __attribute((packed));
>  
>  /*
> - * 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;
> -};
>  
> -
> -static const struct vmstor_protocol vmstor_protocols[] = {
> -	{
> +static const int protocol_version[] = {
>  		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),
> -	}
>  };
>  
>  
> @@ -409,9 +372,7 @@ static void storvsc_on_channel_callback(void *context);
>  #define STORVSC_IDE_MAX_CHANNELS			1
>  
>  /*
> - * 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_SIZE
> - * 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;
>  
> -	/*
> -	 * 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 = num_sc;
>  
>  	ret = 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,
>  			       VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
> @@ -864,8 +813,7 @@ static int storvsc_execute_vstor_op(struct hv_device *device,
>  	vstor_packet->flags = REQUEST_COMPLETION_FLAG;
>  
>  	ret = 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,
>  			       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.
>  	 */
>  
> -	for (i = 0; i < ARRAY_SIZE(vmstor_protocols); i++) {
> +	for (i = 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 =
>  			VSTOR_OPERATION_QUERY_PROTOCOL_VERSION;
>  
> -		vstor_packet->version.major_minor =
> -			vmstor_protocols[i].protocol_version;
> +		vstor_packet->version.major_minor = protocol_version[i];
>  
>  		/*
>  		 * The revision number is only used in Windows; set it to 0.
> @@ -936,14 +883,7 @@ static int storvsc_channel_init(struct hv_device *device, bool is_fc)
>  			return -EINVAL;
>  
>  		if (vstor_packet->status == 0) {
> -			vmstor_proto_version =
> -				vmstor_protocols[i].protocol_version;
> -
> -			sense_buffer_size =
> -				vmstor_protocols[i].sense_buffer_size;
> -
> -			stor_device->vmscsi_size_delta =
> -				vmstor_protocols[i].vmscsi_size_delta;
> +			vmstor_proto_version = protocol_version[i];
>  
>  			break;
>  		}
> @@ -1289,8 +1229,8 @@ static void storvsc_on_channel_callback(void *context)
>  		struct storvsc_cmd_request *request = NULL;
>  		u32 pktlen = hv_pkt_datalen(desc);
>  		u64 rqst_id = desc->trans_id;
> -		u32 minlen = rqst_id ? sizeof(struct vstor_packet) -
> -			stor_device->vmscsi_size_delta : sizeof(enum vstor_packet_operation);
> +		u32 minlen = rqst_id ? sizeof(struct vstor_packet) :
> +			sizeof(enum vstor_packet_operation);
>  
>  		if (pktlen < minlen) {
>  			dev_err(&device->device,
> @@ -1346,7 +1286,7 @@ static void storvsc_on_channel_callback(void *context)
>  		}
>  
>  		memcpy(&request->vstor_packet, packet,
> -		       (sizeof(struct vstor_packet) - stor_device->vmscsi_size_delta));
> +		       sizeof(struct vstor_packet));
>  		complete(&request->wait_event);
>  	}
>  }
> @@ -1557,8 +1497,7 @@ static int storvsc_do_io(struct hv_device *device,
>  found_channel:
>  	vstor_packet->flags |= REQUEST_COMPLETION_FLAG;
>  
> -	vstor_packet->vm_srb.length = (sizeof(struct vmscsi_request) -
> -					stor_device->vmscsi_size_delta);
> +	vstor_packet->vm_srb.length = sizeof(struct vmscsi_request);
>  
>  
>  	vstor_packet->vm_srb.sense_info_length = sense_buffer_size;
> @@ -1574,13 +1513,11 @@ static int storvsc_do_io(struct hv_device *device,
>  		ret = vmbus_sendpacket_mpb_desc(outgoing_channel,
>  				request->payload, request->payload_sz,
>  				vstor_packet,
> -				(sizeof(struct vstor_packet) -
> -				stor_device->vmscsi_size_delta),
> +				sizeof(struct vstor_packet),
>  				(unsigned long)request);
>  	} else {
>  		ret = vmbus_sendpacket(outgoing_channel, vstor_packet,
> -			       (sizeof(struct vstor_packet) -
> -				stor_device->vmscsi_size_delta),
> +			       sizeof(struct vstor_packet),
>  			       (unsigned long)request,
>  			       VM_PKT_DATA_INBAND,
>  			       VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
> @@ -1684,8 +1621,7 @@ static int storvsc_host_reset_handler(struct scsi_cmnd *scmnd)
>  	vstor_packet->vm_srb.path_id = stor_device->path_id;
>  
>  	ret = vmbus_sendpacket(device->channel, vstor_packet,
> -			       (sizeof(struct vstor_packet) -
> -				stor_device->vmscsi_size_delta),
> +			       sizeof(struct vstor_packet),
>  			       VMBUS_RQST_RESET,
>  			       VM_PKT_DATA_INBAND,
>  			       VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
> @@ -1778,31 +1714,31 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
>  
>  	memset(&cmd_request->vstor_packet, 0, sizeof(struct vstor_packet));
>  	vm_srb = &cmd_request->vstor_packet.vm_srb;
> -	vm_srb->win8_extension.time_out_value = 60;
> +	vm_srb->time_out_value = 60;
>  
> -	vm_srb->win8_extension.srb_flags |=
> +	vm_srb->srb_flags |=
>  		SRB_FLAGS_DISABLE_SYNCH_TRANSFER;
>  
>  	if (scmnd->device->tagged_supported) {
> -		vm_srb->win8_extension.srb_flags |=
> +		vm_srb->srb_flags |=
>  		(SRB_FLAGS_QUEUE_ACTION_ENABLE | SRB_FLAGS_NO_QUEUE_FREEZE);
> -		vm_srb->win8_extension.queue_tag = SP_UNTAGGED;
> -		vm_srb->win8_extension.queue_action = SRB_SIMPLE_TAG_REQUEST;
> +		vm_srb->queue_tag = SP_UNTAGGED;
> +		vm_srb->queue_action = SRB_SIMPLE_TAG_REQUEST;
>  	}
>  
>  	/* Build the SRB */
>  	switch (scmnd->sc_data_direction) {
>  	case DMA_TO_DEVICE:
>  		vm_srb->data_in = WRITE_TYPE;
> -		vm_srb->win8_extension.srb_flags |= SRB_FLAGS_DATA_OUT;
> +		vm_srb->srb_flags |= SRB_FLAGS_DATA_OUT;
>  		break;
>  	case DMA_FROM_DEVICE:
>  		vm_srb->data_in = READ_TYPE;
> -		vm_srb->win8_extension.srb_flags |= SRB_FLAGS_DATA_IN;
> +		vm_srb->srb_flags |= SRB_FLAGS_DATA_IN;
>  		break;
>  	case DMA_NONE:
>  		vm_srb->data_in = UNKNOWN_TYPE;
> -		vm_srb->win8_extension.srb_flags |= SRB_FLAGS_NO_DATA_TRANSFER;
> +		vm_srb->srb_flags |= SRB_FLAGS_NO_DATA_TRANSFER;
>  		break;
>  	default:
>  		/*
> @@ -2004,7 +1940,6 @@ static int storvsc_probe(struct hv_device *device,
>  	init_waitqueue_head(&stor_device->waiting_to_drain);
>  	stor_device->device = device;
>  	stor_device->host = host;
> -	stor_device->vmscsi_size_delta = sizeof(struct vmscsi_win8_extension);
>  	spin_lock_init(&stor_device->lock);
>  	hv_set_drvdata(device, stor_device);
>  	dma_set_min_align_mask(&device->device, HV_HYP_PAGE_SIZE - 1);
> @@ -2217,10 +2152,6 @@ static int __init storvsc_drv_init(void)
>  	 * than the ring buffer size since that page is reserved for
>  	 * the ring buffer indices) by the max request size (which is
>  	 * vmbus_channel_packet_multipage_buffer + struct vstor_packet + u64)
> -	 *
> -	 * The computation underestimates max_outstanding_req_per_channel
> -	 * for Win7 and older hosts because it does not take into account
> -	 * the vmscsi_size_delta correction to the max request size.
>  	 */
>  	max_outstanding_req_per_channel =
>  		((storvsc_ringbuffer_size - PAGE_SIZE) /
> -- 
> 2.25.1
>