xen: Add Xen pvSCSI protocol description
Add the definition of pvSCSI protocol used between the pvSCSI frontend in a XEN domU and the pvSCSI backend in a XEN driver domain (usually Dom0). This header was originally provided by Fujitsu for Xen based on Linux 2.6.18. Changes are: - Added comments. - Adapt to Linux style guide. - Add support for larger SG-lists by putting them in an own granted page. - Remove stale definitions. Signed-off-by: Juergen Gross <jgross@suse.com> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
This commit is contained in:
Juergen Gross
Stefano Stabellini
Родитель
854072dd0f
Коммит
e124c9a2c3
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/******************************************************************************
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* vscsiif.h
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*
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* Based on the blkif.h code.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to
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* deal in the Software without restriction, including without limitation the
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* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
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* sell copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*
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* Copyright(c) FUJITSU Limited 2008.
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*/
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#ifndef __XEN__PUBLIC_IO_SCSI_H__
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#define __XEN__PUBLIC_IO_SCSI_H__
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#include "ring.h"
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#include "../grant_table.h"
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/*
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* Feature and Parameter Negotiation
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* =================================
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* The two halves of a Xen pvSCSI driver utilize nodes within the XenStore to
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* communicate capabilities and to negotiate operating parameters. This
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* section enumerates these nodes which reside in the respective front and
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* backend portions of the XenStore, following the XenBus convention.
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*
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* Any specified default value is in effect if the corresponding XenBus node
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* is not present in the XenStore.
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*
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* XenStore nodes in sections marked "PRIVATE" are solely for use by the
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* driver side whose XenBus tree contains them.
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*
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*****************************************************************************
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* Backend XenBus Nodes
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*****************************************************************************
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*
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*------------------ Backend Device Identification (PRIVATE) ------------------
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*
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* p-devname
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* Values: string
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*
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* A free string used to identify the physical device (e.g. a disk name).
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*
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* p-dev
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* Values: string
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*
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* A string specifying the backend device: either a 4-tuple "h:c:t:l"
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* (host, controller, target, lun, all integers), or a WWN (e.g.
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* "naa.60014054ac780582").
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*
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* v-dev
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* Values: string
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*
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* A string specifying the frontend device in form of a 4-tuple "h:c:t:l"
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* (host, controller, target, lun, all integers).
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*
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*--------------------------------- Features ---------------------------------
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*
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* feature-sg-grant
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* Values: unsigned [VSCSIIF_SG_TABLESIZE...65535]
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* Default Value: 0
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*
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* Specifies the maximum number of scatter/gather elements in grant pages
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* supported. If not set, the backend supports up to VSCSIIF_SG_TABLESIZE
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* SG elements specified directly in the request.
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*
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*****************************************************************************
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* Frontend XenBus Nodes
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*****************************************************************************
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*
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*----------------------- Request Transport Parameters -----------------------
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*
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* event-channel
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* Values: unsigned
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*
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* The identifier of the Xen event channel used to signal activity
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* in the ring buffer.
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*
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* ring-ref
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* Values: unsigned
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*
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* The Xen grant reference granting permission for the backend to map
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* the sole page in a single page sized ring buffer.
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*
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* protocol
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* Values: string (XEN_IO_PROTO_ABI_*)
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* Default Value: XEN_IO_PROTO_ABI_NATIVE
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*
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* The machine ABI rules governing the format of all ring request and
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* response structures.
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*/
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/* Requests from the frontend to the backend */
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/*
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* Request a SCSI operation specified via a CDB in vscsiif_request.cmnd.
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* The target is specified via channel, id and lun.
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*
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* The operation to be performed is specified via a CDB in cmnd[], the length
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* of the CDB is in cmd_len. sc_data_direction specifies the direction of data
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* (to the device, from the device, or none at all).
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*
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* If data is to be transferred to or from the device the buffer(s) in the
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* guest memory is/are specified via one or multiple scsiif_request_segment
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* descriptors each specifying a memory page via a grant_ref_t, a offset into
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* the page and the length of the area in that page. All scsiif_request_segment
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* areas concatenated form the resulting data buffer used by the operation.
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* If the number of scsiif_request_segment areas is not too large (less than
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* or equal VSCSIIF_SG_TABLESIZE) the areas can be specified directly in the
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* seg[] array and the number of valid scsiif_request_segment elements is to be
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* set in nr_segments.
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*
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* If "feature-sg-grant" in the Xenstore is set it is possible to specify more
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* than VSCSIIF_SG_TABLESIZE scsiif_request_segment elements via indirection.
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* The maximum number of allowed scsiif_request_segment elements is the value
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* of the "feature-sg-grant" entry from Xenstore. When using indirection the
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* seg[] array doesn't contain specifications of the data buffers, but
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* references to scsiif_request_segment arrays, which in turn reference the
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* data buffers. While nr_segments holds the number of populated seg[] entries
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* (plus the set VSCSIIF_SG_GRANT bit), the number of scsiif_request_segment
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* elements referencing the target data buffers is calculated from the lengths
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* of the seg[] elements (the sum of all valid seg[].length divided by the
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* size of one scsiif_request_segment structure).
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*/
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#define VSCSIIF_ACT_SCSI_CDB 1
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/*
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* Request abort of a running operation for the specified target given by
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* channel, id, lun and the operation's rqid in ref_rqid.
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*/
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#define VSCSIIF_ACT_SCSI_ABORT 2
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/*
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* Request a device reset of the specified target (channel and id).
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*/
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#define VSCSIIF_ACT_SCSI_RESET 3
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/*
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* Preset scatter/gather elements for a following request. Deprecated.
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* Keeping the define only to avoid usage of the value "4" for other actions.
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*/
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#define VSCSIIF_ACT_SCSI_SG_PRESET 4
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/*
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* Maximum scatter/gather segments per request.
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*
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* Considering balance between allocating at least 16 "vscsiif_request"
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* structures on one page (4096 bytes) and the number of scatter/gather
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* elements needed, we decided to use 26 as a magic number.
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*
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* If "feature-sg-grant" is set, more scatter/gather elements can be specified
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* by placing them in one or more (up to VSCSIIF_SG_TABLESIZE) granted pages.
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* In this case the vscsiif_request seg elements don't contain references to
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* the user data, but to the SG elements referencing the user data.
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*/
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#define VSCSIIF_SG_TABLESIZE 26
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/*
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* based on Linux kernel 2.6.18, still valid
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* Changing these values requires support of multiple protocols via the rings
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* as "old clients" will blindly use these values and the resulting structure
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* sizes.
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*/
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#define VSCSIIF_MAX_COMMAND_SIZE 16
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#define VSCSIIF_SENSE_BUFFERSIZE 96
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struct scsiif_request_segment {
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grant_ref_t gref;
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uint16_t offset;
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uint16_t length;
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};
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#define VSCSIIF_SG_PER_PAGE (PAGE_SIZE / sizeof(struct scsiif_request_segment))
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/* Size of one request is 252 bytes */
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struct vscsiif_request {
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uint16_t rqid; /* private guest value, echoed in resp */
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uint8_t act; /* command between backend and frontend */
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uint8_t cmd_len; /* valid CDB bytes */
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uint8_t cmnd[VSCSIIF_MAX_COMMAND_SIZE]; /* the CDB */
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uint16_t timeout_per_command; /* deprecated */
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uint16_t channel, id, lun; /* (virtual) device specification */
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uint16_t ref_rqid; /* command abort reference */
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uint8_t sc_data_direction; /* for DMA_TO_DEVICE(1)
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DMA_FROM_DEVICE(2)
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DMA_NONE(3) requests */
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uint8_t nr_segments; /* Number of pieces of scatter-gather */
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/*
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* flag in nr_segments: SG elements via grant page
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*
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* If VSCSIIF_SG_GRANT is set, the low 7 bits of nr_segments specify the number
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* of grant pages containing SG elements. Usable if "feature-sg-grant" set.
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*/
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#define VSCSIIF_SG_GRANT 0x80
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struct scsiif_request_segment seg[VSCSIIF_SG_TABLESIZE];
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uint32_t reserved[3];
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};
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/* Size of one response is 252 bytes */
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struct vscsiif_response {
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uint16_t rqid; /* identifies request */
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uint8_t padding;
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uint8_t sense_len;
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uint8_t sense_buffer[VSCSIIF_SENSE_BUFFERSIZE];
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int32_t rslt;
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uint32_t residual_len; /* request bufflen -
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return the value from physical device */
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uint32_t reserved[36];
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};
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DEFINE_RING_TYPES(vscsiif, struct vscsiif_request, struct vscsiif_response);
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#endif /*__XEN__PUBLIC_IO_SCSI_H__*/
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