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/* SPDX-License-Identifier: MIT */
* vscsiif.h
* Based on the blkif.h code.
* Copyright(c) FUJITSU Limited 2008.
#ifndef __XEN__PUBLIC_IO_SCSI_H__
#define __XEN__PUBLIC_IO_SCSI_H__
#include "ring.h"
#include "../grant_table.h"
* Feature and Parameter Negotiation
* =================================
* The two halves of a Xen pvSCSI driver utilize nodes within the XenStore to
* communicate capabilities and to negotiate operating parameters. This
* section enumerates these nodes which reside in the respective front and
* backend portions of the XenStore, following the XenBus convention.
* Any specified default value is in effect if the corresponding XenBus node
* is not present in the XenStore.
* XenStore nodes in sections marked "PRIVATE" are solely for use by the
* driver side whose XenBus tree contains them.
* Backend XenBus Nodes
*------------------ Backend Device Identification (PRIVATE) ------------------
* p-devname
* Values: string
* A free string used to identify the physical device (e.g. a disk name).
* p-dev
* Values: string
* A string specifying the backend device: either a 4-tuple "h:c:t:l"
* (host, controller, target, lun, all integers), or a WWN (e.g.
* "naa.60014054ac780582").
* v-dev
* Values: string
* A string specifying the frontend device in form of a 4-tuple "h:c:t:l"
* (host, controller, target, lun, all integers).
*--------------------------------- Features ---------------------------------
* feature-sg-grant
* Values: unsigned [VSCSIIF_SG_TABLESIZE...65535]
* Default Value: 0
* Specifies the maximum number of scatter/gather elements in grant pages
* supported. If not set, the backend supports up to VSCSIIF_SG_TABLESIZE
* SG elements specified directly in the request.
* Frontend XenBus Nodes
*----------------------- Request Transport Parameters -----------------------
* event-channel
* Values: unsigned
* The identifier of the Xen event channel used to signal activity
* in the ring buffer.
* ring-ref
* Values: unsigned
* The Xen grant reference granting permission for the backend to map
* the sole page in a single page sized ring buffer.
* protocol
* Values: string (XEN_IO_PROTO_ABI_*)
* The machine ABI rules governing the format of all ring request and
* response structures.
/* Requests from the frontend to the backend */
* Request a SCSI operation specified via a CDB in vscsiif_request.cmnd.
* The target is specified via channel, id and lun.
* The operation to be performed is specified via a CDB in cmnd[], the length
* of the CDB is in cmd_len. sc_data_direction specifies the direction of data
* (to the device, from the device, or none at all).
* If data is to be transferred to or from the device the buffer(s) in the
* guest memory is/are specified via one or multiple scsiif_request_segment
* descriptors each specifying a memory page via a grant_ref_t, a offset into
* the page and the length of the area in that page. All scsiif_request_segment
* areas concatenated form the resulting data buffer used by the operation.
* If the number of scsiif_request_segment areas is not too large (less than
* or equal VSCSIIF_SG_TABLESIZE) the areas can be specified directly in the
* seg[] array and the number of valid scsiif_request_segment elements is to be
* set in nr_segments.
* If "feature-sg-grant" in the Xenstore is set it is possible to specify more
* than VSCSIIF_SG_TABLESIZE scsiif_request_segment elements via indirection.
* The maximum number of allowed scsiif_request_segment elements is the value
* of the "feature-sg-grant" entry from Xenstore. When using indirection the
* seg[] array doesn't contain specifications of the data buffers, but
* references to scsiif_request_segment arrays, which in turn reference the
* data buffers. While nr_segments holds the number of populated seg[] entries
* (plus the set VSCSIIF_SG_GRANT bit), the number of scsiif_request_segment
* elements referencing the target data buffers is calculated from the lengths
* of the seg[] elements (the sum of all valid seg[].length divided by the
* size of one scsiif_request_segment structure).
* Request abort of a running operation for the specified target given by
* channel, id, lun and the operation's rqid in ref_rqid.
* Request a device reset of the specified target (channel and id).
* Preset scatter/gather elements for a following request. Deprecated.
* Keeping the define only to avoid usage of the value "4" for other actions.
* Maximum scatter/gather segments per request.
* Considering balance between allocating at least 16 "vscsiif_request"
* structures on one page (4096 bytes) and the number of scatter/gather
* elements needed, we decided to use 26 as a magic number.
* If "feature-sg-grant" is set, more scatter/gather elements can be specified
* by placing them in one or more (up to VSCSIIF_SG_TABLESIZE) granted pages.
* In this case the vscsiif_request seg elements don't contain references to
* the user data, but to the SG elements referencing the user data.
* based on Linux kernel 2.6.18, still valid
* Changing these values requires support of multiple protocols via the rings
* as "old clients" will blindly use these values and the resulting structure
* sizes.
struct scsiif_request_segment {
grant_ref_t gref;
uint16_t offset;
uint16_t length;
#define VSCSIIF_SG_PER_PAGE (PAGE_SIZE / sizeof(struct scsiif_request_segment))
/* Size of one request is 252 bytes */
struct vscsiif_request {
uint16_t rqid; /* private guest value, echoed in resp */
uint8_t act; /* command between backend and frontend */
uint8_t cmd_len; /* valid CDB bytes */
uint8_t cmnd[VSCSIIF_MAX_COMMAND_SIZE]; /* the CDB */
uint16_t timeout_per_command; /* deprecated */
uint16_t channel, id, lun; /* (virtual) device specification */
uint16_t ref_rqid; /* command abort reference */
uint8_t sc_data_direction; /* for DMA_TO_DEVICE(1)
DMA_NONE(3) requests */
uint8_t nr_segments; /* Number of pieces of scatter-gather */
* flag in nr_segments: SG elements via grant page
* If VSCSIIF_SG_GRANT is set, the low 7 bits of nr_segments specify the number
* of grant pages containing SG elements. Usable if "feature-sg-grant" set.
#define VSCSIIF_SG_GRANT 0x80
struct scsiif_request_segment seg[VSCSIIF_SG_TABLESIZE];
uint32_t reserved[3];
/* Size of one response is 252 bytes */
struct vscsiif_response {
uint16_t rqid; /* identifies request */
uint8_t padding;
uint8_t sense_len;
uint8_t sense_buffer[VSCSIIF_SENSE_BUFFERSIZE];
int32_t rslt;
uint32_t residual_len; /* request bufflen -
return the value from physical device */
uint32_t reserved[36];
DEFINE_RING_TYPES(vscsiif, struct vscsiif_request, struct vscsiif_response);
#endif /*__XEN__PUBLIC_IO_SCSI_H__*/