| /****************************************************************************** |
| * blkif.h |
| * |
| * Unified block-device I/O interface for Xen guest OSes. |
| * |
| * Permission is hereby granted, free of charge, to any person obtaining a copy |
| * of this software and associated documentation files (the "Software"), to |
| * deal in the Software without restriction, including without limitation the |
| * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or |
| * sell copies of the Software, and to permit persons to whom the Software is |
| * furnished to do so, subject to the following conditions: |
| * |
| * The above copyright notice and this permission notice shall be included in |
| * all copies or substantial portions of the Software. |
| * |
| * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
| * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER |
| * DEALINGS IN THE SOFTWARE. |
| * |
| * Copyright (c) 2003-2004, Keir Fraser |
| * Copyright (c) 2012, Spectra Logic Corporation |
| */ |
| |
| #ifndef __XEN_PUBLIC_IO_BLKIF_H__ |
| #define __XEN_PUBLIC_IO_BLKIF_H__ |
| |
| #include "ring.h" |
| #include "../grant_table.h" |
| |
| /* |
| * Front->back notifications: When enqueuing a new request, sending a |
| * notification can be made conditional on req_event (i.e., the generic |
| * hold-off mechanism provided by the ring macros). Backends must set |
| * req_event appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()). |
| * |
| * Back->front notifications: When enqueuing a new response, sending a |
| * notification can be made conditional on rsp_event (i.e., the generic |
| * hold-off mechanism provided by the ring macros). Frontends must set |
| * rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()). |
| */ |
| |
| #ifndef blkif_vdev_t |
| #define blkif_vdev_t uint16_t |
| #endif |
| #define blkif_sector_t uint64_t |
| |
| /* |
| * Feature and Parameter Negotiation |
| * ================================= |
| * The two halves of a Xen block 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. |
| * |
| * All data in the XenStore is stored as strings. Nodes specifying numeric |
| * values are encoded in decimal. Integer value ranges listed below are |
| * expressed as fixed sized integer types capable of storing the conversion |
| * of a properly formated node string, without loss of information. |
| * |
| * 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. |
| * |
| * XenStore nodes marked "DEPRECATED" in their notes section should only be |
| * used to provide interoperability with legacy implementations. |
| * |
| * See the XenBus state transition diagram below for details on when XenBus |
| * nodes must be published and when they can be queried. |
| * |
| ***************************************************************************** |
| * Backend XenBus Nodes |
| ***************************************************************************** |
| * |
| *------------------ Backend Device Identification (PRIVATE) ------------------ |
| * |
| * mode |
| * Values: "r" (read only), "w" (writable) |
| * |
| * The read or write access permissions to the backing store to be |
| * granted to the frontend. |
| * |
| * params |
| * Values: string |
| * |
| * A free formatted string providing sufficient information for the |
| * hotplug script to attach the device and provide a suitable |
| * handler (ie: a block device) for blkback to use. |
| * |
| * physical-device |
| * Values: "MAJOR:MINOR" |
| * Notes: 11 |
| * |
| * MAJOR and MINOR are the major number and minor number of the |
| * backing device respectively. |
| * |
| * physical-device-path |
| * Values: path string |
| * |
| * A string that contains the absolute path to the disk image. On |
| * NetBSD and Linux this is always a block device, while on FreeBSD |
| * it can be either a block device or a regular file. |
| * |
| * type |
| * Values: "file", "phy", "tap" |
| * |
| * The type of the backing device/object. |
| * |
| * |
| * direct-io-safe |
| * Values: 0/1 (boolean) |
| * Default Value: 0 |
| * |
| * The underlying storage is not affected by the direct IO memory |
| * lifetime bug. See: |
| * https://lists.xen.org/archives/html/xen-devel/2012-12/msg01154.html |
| * |
| * Therefore this option gives the backend permission to use |
| * O_DIRECT, notwithstanding that bug. |
| * |
| * That is, if this option is enabled, use of O_DIRECT is safe, |
| * in circumstances where we would normally have avoided it as a |
| * workaround for that bug. This option is not relevant for all |
| * backends, and even not necessarily supported for those for |
| * which it is relevant. A backend which knows that it is not |
| * affected by the bug can ignore this option. |
| * |
| * This option doesn't require a backend to use O_DIRECT, so it |
| * should not be used to try to control the caching behaviour. |
| * |
| *--------------------------------- Features --------------------------------- |
| * |
| * feature-barrier |
| * Values: 0/1 (boolean) |
| * Default Value: 0 |
| * |
| * A value of "1" indicates that the backend can process requests |
| * containing the BLKIF_OP_WRITE_BARRIER request opcode. Requests |
| * of this type may still be returned at any time with the |
| * BLKIF_RSP_EOPNOTSUPP result code. |
| * |
| * feature-flush-cache |
| * Values: 0/1 (boolean) |
| * Default Value: 0 |
| * |
| * A value of "1" indicates that the backend can process requests |
| * containing the BLKIF_OP_FLUSH_DISKCACHE request opcode. Requests |
| * of this type may still be returned at any time with the |
| * BLKIF_RSP_EOPNOTSUPP result code. |
| * |
| * feature-discard |
| * Values: 0/1 (boolean) |
| * Default Value: 0 |
| * |
| * A value of "1" indicates that the backend can process requests |
| * containing the BLKIF_OP_DISCARD request opcode. Requests |
| * of this type may still be returned at any time with the |
| * BLKIF_RSP_EOPNOTSUPP result code. |
| * |
| * feature-persistent |
| * Values: 0/1 (boolean) |
| * Default Value: 0 |
| * Notes: 7 |
| * |
| * A value of "1" indicates that the backend can keep the grants used |
| * by the frontend driver mapped, so the same set of grants should be |
| * used in all transactions. The maximum number of grants the backend |
| * can map persistently depends on the implementation, but ideally it |
| * should be RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. Using this |
| * feature the backend doesn't need to unmap each grant, preventing |
| * costly TLB flushes. The backend driver should only map grants |
| * persistently if the frontend supports it. If a backend driver chooses |
| * to use the persistent protocol when the frontend doesn't support it, |
| * it will probably hit the maximum number of persistently mapped grants |
| * (due to the fact that the frontend won't be reusing the same grants), |
| * and fall back to non-persistent mode. Backend implementations may |
| * shrink or expand the number of persistently mapped grants without |
| * notifying the frontend depending on memory constraints (this might |
| * cause a performance degradation). |
| * |
| * If a backend driver wants to limit the maximum number of persistently |
| * mapped grants to a value less than RING_SIZE * |
| * BLKIF_MAX_SEGMENTS_PER_REQUEST a LRU strategy should be used to |
| * discard the grants that are less commonly used. Using a LRU in the |
| * backend driver paired with a LIFO queue in the frontend will |
| * allow us to have better performance in this scenario. |
| * |
| *----------------------- Request Transport Parameters ------------------------ |
| * |
| * max-ring-page-order |
| * Values: <uint32_t> |
| * Default Value: 0 |
| * Notes: 1, 3 |
| * |
| * The maximum supported size of the request ring buffer in units of |
| * lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages, |
| * etc.). |
| * |
| * max-ring-pages |
| * Values: <uint32_t> |
| * Default Value: 1 |
| * Notes: DEPRECATED, 2, 3 |
| * |
| * The maximum supported size of the request ring buffer in units of |
| * machine pages. The value must be a power of 2. |
| * |
| *------------------------- Backend Device Properties ------------------------- |
| * |
| * discard-enable |
| * Values: 0/1 (boolean) |
| * Default Value: 1 |
| * |
| * This optional property, set by the toolstack, instructs the backend |
| * to offer (or not to offer) discard to the frontend. If the property |
| * is missing the backend should offer discard if the backing storage |
| * actually supports it. |
| * |
| * discard-alignment |
| * Values: <uint32_t> |
| * Default Value: 0 |
| * Notes: 4, 5 |
| * |
| * The offset, in bytes from the beginning of the virtual block device, |
| * to the first, addressable, discard extent on the underlying device. |
| * |
| * discard-granularity |
| * Values: <uint32_t> |
| * Default Value: <"sector-size"> |
| * Notes: 4 |
| * |
| * The size, in bytes, of the individually addressable discard extents |
| * of the underlying device. |
| * |
| * discard-secure |
| * Values: 0/1 (boolean) |
| * Default Value: 0 |
| * Notes: 10 |
| * |
| * A value of "1" indicates that the backend can process BLKIF_OP_DISCARD |
| * requests with the BLKIF_DISCARD_SECURE flag set. |
| * |
| * info |
| * Values: <uint32_t> (bitmap) |
| * |
| * A collection of bit flags describing attributes of the backing |
| * device. The VDISK_* macros define the meaning of each bit |
| * location. |
| * |
| * sector-size |
| * Values: <uint32_t> |
| * |
| * The logical block size, in bytes, of the underlying storage. This |
| * must be a power of two with a minimum value of 512. |
| * |
| * NOTE: Because of implementation bugs in some frontends this must be |
| * set to 512, unless the frontend advertizes a non-zero value |
| * in its "feature-large-sector-size" xenbus node. (See below). |
| * |
| * physical-sector-size |
| * Values: <uint32_t> |
| * Default Value: <"sector-size"> |
| * |
| * The physical block size, in bytes, of the backend storage. This |
| * must be an integer multiple of "sector-size". |
| * |
| * sectors |
| * Values: <uint64_t> |
| * |
| * The size of the backend device, expressed in units of "sector-size". |
| * The product of "sector-size" and "sectors" must also be an integer |
| * multiple of "physical-sector-size", if that node is present. |
| * |
| ***************************************************************************** |
| * Frontend XenBus Nodes |
| ***************************************************************************** |
| * |
| *----------------------- Request Transport Parameters ----------------------- |
| * |
| * event-channel |
| * Values: <uint32_t> |
| * |
| * The identifier of the Xen event channel used to signal activity |
| * in the ring buffer. |
| * |
| * ring-ref |
| * Values: <uint32_t> |
| * Notes: 6 |
| * |
| * The Xen grant reference granting permission for the backend to map |
| * the sole page in a single page sized ring buffer. |
| * |
| * ring-ref%u |
| * Values: <uint32_t> |
| * Notes: 6 |
| * |
| * For a frontend providing a multi-page ring, a "number of ring pages" |
| * sized list of nodes, each containing a Xen grant reference granting |
| * permission for the backend to map the page of the ring located |
| * at page index "%u". Page indexes are zero based. |
| * |
| * protocol |
| * Values: string (XEN_IO_PROTO_ABI_*) |
| * Default Value: XEN_IO_PROTO_ABI_NATIVE |
| * |
| * The machine ABI rules governing the format of all ring request and |
| * response structures. |
| * |
| * ring-page-order |
| * Values: <uint32_t> |
| * Default Value: 0 |
| * Maximum Value: MAX(ffs(max-ring-pages) - 1, max-ring-page-order) |
| * Notes: 1, 3 |
| * |
| * The size of the frontend allocated request ring buffer in units |
| * of lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages, |
| * etc.). |
| * |
| * num-ring-pages |
| * Values: <uint32_t> |
| * Default Value: 1 |
| * Maximum Value: MAX(max-ring-pages,(0x1 << max-ring-page-order)) |
| * Notes: DEPRECATED, 2, 3 |
| * |
| * The size of the frontend allocated request ring buffer in units of |
| * machine pages. The value must be a power of 2. |
| * |
| *--------------------------------- Features --------------------------------- |
| * |
| * feature-persistent |
| * Values: 0/1 (boolean) |
| * Default Value: 0 |
| * Notes: 7, 8, 9 |
| * |
| * A value of "1" indicates that the frontend will reuse the same grants |
| * for all transactions, allowing the backend to map them with write |
| * access (even when it should be read-only). If the frontend hits the |
| * maximum number of allowed persistently mapped grants, it can fallback |
| * to non persistent mode. This will cause a performance degradation, |
| * since the the backend driver will still try to map those grants |
| * persistently. Since the persistent grants protocol is compatible with |
| * the previous protocol, a frontend driver can choose to work in |
| * persistent mode even when the backend doesn't support it. |
| * |
| * It is recommended that the frontend driver stores the persistently |
| * mapped grants in a LIFO queue, so a subset of all persistently mapped |
| * grants gets used commonly. This is done in case the backend driver |
| * decides to limit the maximum number of persistently mapped grants |
| * to a value less than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. |
| * |
| * feature-large-sector-size |
| * Values: 0/1 (boolean) |
| * Default Value: 0 |
| * |
| * A value of "1" indicates that the frontend will correctly supply and |
| * interpret all sector-based quantities in terms of the "sector-size" |
| * value supplied in the backend info, whatever that may be set to. |
| * If this node is not present or its value is "0" then it is assumed |
| * that the frontend requires that the logical block size is 512 as it |
| * is hardcoded (which is the case in some frontend implementations). |
| * |
| *------------------------- Virtual Device Properties ------------------------- |
| * |
| * device-type |
| * Values: "disk", "cdrom", "floppy", etc. |
| * |
| * virtual-device |
| * Values: <uint32_t> |
| * |
| * A value indicating the physical device to virtualize within the |
| * frontend's domain. (e.g. "The first ATA disk", "The third SCSI |
| * disk", etc.) |
| * |
| * See docs/misc/vbd-interface.txt for details on the format of this |
| * value. |
| * |
| * Notes |
| * ----- |
| * (1) Multi-page ring buffer scheme first developed in the Citrix XenServer |
| * PV drivers. |
| * (2) Multi-page ring buffer scheme first used in some RedHat distributions |
| * including a distribution deployed on certain nodes of the Amazon |
| * EC2 cluster. |
| * (3) Support for multi-page ring buffers was implemented independently, |
| * in slightly different forms, by both Citrix and RedHat/Amazon. |
| * For full interoperability, block front and backends should publish |
| * identical ring parameters, adjusted for unit differences, to the |
| * XenStore nodes used in both schemes. |
| * (4) Devices that support discard functionality may internally allocate space |
| * (discardable extents) in units that are larger than the exported logical |
| * block size. If the backing device has such discardable extents the |
| * backend should provide both discard-granularity and discard-alignment. |
| * Providing just one of the two may be considered an error by the frontend. |
| * Backends supporting discard should include discard-granularity and |
| * discard-alignment even if it supports discarding individual sectors. |
| * Frontends should assume discard-alignment == 0 and discard-granularity |
| * == sector size if these keys are missing. |
| * (5) The discard-alignment parameter allows a physical device to be |
| * partitioned into virtual devices that do not necessarily begin or |
| * end on a discardable extent boundary. |
| * (6) When there is only a single page allocated to the request ring, |
| * 'ring-ref' is used to communicate the grant reference for this |
| * page to the backend. When using a multi-page ring, the 'ring-ref' |
| * node is not created. Instead 'ring-ref0' - 'ring-refN' are used. |
| * (7) When using persistent grants data has to be copied from/to the page |
| * where the grant is currently mapped. The overhead of doing this copy |
| * however doesn't suppress the speed improvement of not having to unmap |
| * the grants. |
| * (8) The frontend driver has to allow the backend driver to map all grants |
| * with write access, even when they should be mapped read-only, since |
| * further requests may reuse these grants and require write permissions. |
| * (9) Linux implementation doesn't have a limit on the maximum number of |
| * grants that can be persistently mapped in the frontend driver, but |
| * due to the frontent driver implementation it should never be bigger |
| * than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. |
| *(10) The discard-secure property may be present and will be set to 1 if the |
| * backing device supports secure discard. |
| *(11) Only used by Linux and NetBSD. |
| */ |
| |
| /* |
| * Multiple hardware queues/rings: |
| * If supported, the backend will write the key "multi-queue-max-queues" to |
| * the directory for that vbd, and set its value to the maximum supported |
| * number of queues. |
| * Frontends that are aware of this feature and wish to use it can write the |
| * key "multi-queue-num-queues" with the number they wish to use, which must be |
| * greater than zero, and no more than the value reported by the backend in |
| * "multi-queue-max-queues". |
| * |
| * For frontends requesting just one queue, the usual event-channel and |
| * ring-ref keys are written as before, simplifying the backend processing |
| * to avoid distinguishing between a frontend that doesn't understand the |
| * multi-queue feature, and one that does, but requested only one queue. |
| * |
| * Frontends requesting two or more queues must not write the toplevel |
| * event-channel and ring-ref keys, instead writing those keys under sub-keys |
| * having the name "queue-N" where N is the integer ID of the queue/ring for |
| * which those keys belong. Queues are indexed from zero. |
| * For example, a frontend with two queues must write the following set of |
| * queue-related keys: |
| * |
| * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2" |
| * /local/domain/1/device/vbd/0/queue-0 = "" |
| * /local/domain/1/device/vbd/0/queue-0/ring-ref = "<ring-ref#0>" |
| * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>" |
| * /local/domain/1/device/vbd/0/queue-1 = "" |
| * /local/domain/1/device/vbd/0/queue-1/ring-ref = "<ring-ref#1>" |
| * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>" |
| * |
| * It is also possible to use multiple queues/rings together with |
| * feature multi-page ring buffer. |
| * For example, a frontend requests two queues/rings and the size of each ring |
| * buffer is two pages must write the following set of related keys: |
| * |
| * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2" |
| * /local/domain/1/device/vbd/0/ring-page-order = "1" |
| * /local/domain/1/device/vbd/0/queue-0 = "" |
| * /local/domain/1/device/vbd/0/queue-0/ring-ref0 = "<ring-ref#0>" |
| * /local/domain/1/device/vbd/0/queue-0/ring-ref1 = "<ring-ref#1>" |
| * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>" |
| * /local/domain/1/device/vbd/0/queue-1 = "" |
| * /local/domain/1/device/vbd/0/queue-1/ring-ref0 = "<ring-ref#2>" |
| * /local/domain/1/device/vbd/0/queue-1/ring-ref1 = "<ring-ref#3>" |
| * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>" |
| * |
| */ |
| |
| /* |
| * STATE DIAGRAMS |
| * |
| ***************************************************************************** |
| * Startup * |
| ***************************************************************************** |
| * |
| * Tool stack creates front and back nodes with state XenbusStateInitialising. |
| * |
| * Front Back |
| * ================================= ===================================== |
| * XenbusStateInitialising XenbusStateInitialising |
| * o Query virtual device o Query backend device identification |
| * properties. data. |
| * o Setup OS device instance. o Open and validate backend device. |
| * o Publish backend features and |
| * transport parameters. |
| * | |
| * | |
| * V |
| * XenbusStateInitWait |
| * |
| * o Query backend features and |
| * transport parameters. |
| * o Allocate and initialize the |
| * request ring. |
| * o Publish transport parameters |
| * that will be in effect during |
| * this connection. |
| * | |
| * | |
| * V |
| * XenbusStateInitialised |
| * |
| * o Query frontend transport parameters. |
| * o Connect to the request ring and |
| * event channel. |
| * o Publish backend device properties. |
| * | |
| * | |
| * V |
| * XenbusStateConnected |
| * |
| * o Query backend device properties. |
| * o Finalize OS virtual device |
| * instance. |
| * | |
| * | |
| * V |
| * XenbusStateConnected |
| * |
| * Note: Drivers that do not support any optional features, or the negotiation |
| * of transport parameters, can skip certain states in the state machine: |
| * |
| * o A frontend may transition to XenbusStateInitialised without |
| * waiting for the backend to enter XenbusStateInitWait. In this |
| * case, default transport parameters are in effect and any |
| * transport parameters published by the frontend must contain |
| * their default values. |
| * |
| * o A backend may transition to XenbusStateInitialised, bypassing |
| * XenbusStateInitWait, without waiting for the frontend to first |
| * enter the XenbusStateInitialised state. In this case, default |
| * transport parameters are in effect and any transport parameters |
| * published by the backend must contain their default values. |
| * |
| * Drivers that support optional features and/or transport parameter |
| * negotiation must tolerate these additional state transition paths. |
| * In general this means performing the work of any skipped state |
| * transition, if it has not already been performed, in addition to the |
| * work associated with entry into the current state. |
| */ |
| |
| /* |
| * REQUEST CODES. |
| */ |
| #define BLKIF_OP_READ 0 |
| #define BLKIF_OP_WRITE 1 |
| /* |
| * All writes issued prior to a request with the BLKIF_OP_WRITE_BARRIER |
| * operation code ("barrier request") must be completed prior to the |
| * execution of the barrier request. All writes issued after the barrier |
| * request must not execute until after the completion of the barrier request. |
| * |
| * Optional. See "feature-barrier" XenBus node documentation above. |
| */ |
| #define BLKIF_OP_WRITE_BARRIER 2 |
| /* |
| * Commit any uncommitted contents of the backing device's volatile cache |
| * to stable storage. |
| * |
| * Optional. See "feature-flush-cache" XenBus node documentation above. |
| */ |
| #define BLKIF_OP_FLUSH_DISKCACHE 3 |
| /* |
| * Used in SLES sources for device specific command packet |
| * contained within the request. Reserved for that purpose. |
| */ |
| #define BLKIF_OP_RESERVED_1 4 |
| /* |
| * Indicate to the backend device that a region of storage is no longer in |
| * use, and may be discarded at any time without impact to the client. If |
| * the BLKIF_DISCARD_SECURE flag is set on the request, all copies of the |
| * discarded region on the device must be rendered unrecoverable before the |
| * command returns. |
| * |
| * This operation is analogous to performing a trim (ATA) or unamp (SCSI), |
| * command on a native device. |
| * |
| * More information about trim/unmap operations can be found at: |
| * http://t13.org/Documents/UploadedDocuments/docs2008/ |
| * e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc |
| * http://www.seagate.com/staticfiles/support/disc/manuals/ |
| * Interface%20manuals/100293068c.pdf |
| * |
| * Optional. See "feature-discard", "discard-alignment", |
| * "discard-granularity", and "discard-secure" in the XenBus node |
| * documentation above. |
| */ |
| #define BLKIF_OP_DISCARD 5 |
| |
| /* |
| * Recognized if "feature-max-indirect-segments" in present in the backend |
| * xenbus info. The "feature-max-indirect-segments" node contains the maximum |
| * number of segments allowed by the backend per request. If the node is |
| * present, the frontend might use blkif_request_indirect structs in order to |
| * issue requests with more than BLKIF_MAX_SEGMENTS_PER_REQUEST (11). The |
| * maximum number of indirect segments is fixed by the backend, but the |
| * frontend can issue requests with any number of indirect segments as long as |
| * it's less than the number provided by the backend. The indirect_grefs field |
| * in blkif_request_indirect should be filled by the frontend with the |
| * grant references of the pages that are holding the indirect segments. |
| * These pages are filled with an array of blkif_request_segment that hold the |
| * information about the segments. The number of indirect pages to use is |
| * determined by the number of segments an indirect request contains. Every |
| * indirect page can contain a maximum of |
| * (PAGE_SIZE / sizeof(struct blkif_request_segment)) segments, so to |
| * calculate the number of indirect pages to use we have to do |
| * ceil(indirect_segments / (PAGE_SIZE / sizeof(struct blkif_request_segment))). |
| * |
| * If a backend does not recognize BLKIF_OP_INDIRECT, it should *not* |
| * create the "feature-max-indirect-segments" node! |
| */ |
| #define BLKIF_OP_INDIRECT 6 |
| |
| /* |
| * Maximum scatter/gather segments per request. |
| * This is carefully chosen so that sizeof(blkif_ring_t) <= PAGE_SIZE. |
| * NB. This could be 12 if the ring indexes weren't stored in the same page. |
| */ |
| #define BLKIF_MAX_SEGMENTS_PER_REQUEST 11 |
| |
| /* |
| * Maximum number of indirect pages to use per request. |
| */ |
| #define BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST 8 |
| |
| /* |
| * NB. 'first_sect' and 'last_sect' in blkif_request_segment, as well as |
| * 'sector_number' in blkif_request, blkif_request_discard and |
| * blkif_request_indirect are sector-based quantities. See the description |
| * of the "feature-large-sector-size" frontend xenbus node above for |
| * more information. |
| */ |
| struct blkif_request_segment { |
| grant_ref_t gref; /* reference to I/O buffer frame */ |
| /* @first_sect: first sector in frame to transfer (inclusive). */ |
| /* @last_sect: last sector in frame to transfer (inclusive). */ |
| uint8_t first_sect, last_sect; |
| }; |
| |
| /* |
| * Starting ring element for any I/O request. |
| */ |
| struct blkif_request { |
| uint8_t operation; /* BLKIF_OP_??? */ |
| uint8_t nr_segments; /* number of segments */ |
| blkif_vdev_t handle; /* only for read/write requests */ |
| uint64_t id; /* private guest value, echoed in resp */ |
| blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */ |
| struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST]; |
| }; |
| typedef struct blkif_request blkif_request_t; |
| |
| /* |
| * Cast to this structure when blkif_request.operation == BLKIF_OP_DISCARD |
| * sizeof(struct blkif_request_discard) <= sizeof(struct blkif_request) |
| */ |
| struct blkif_request_discard { |
| uint8_t operation; /* BLKIF_OP_DISCARD */ |
| uint8_t flag; /* BLKIF_DISCARD_SECURE or zero */ |
| #define BLKIF_DISCARD_SECURE (1<<0) /* ignored if discard-secure=0 */ |
| blkif_vdev_t handle; /* same as for read/write requests */ |
| uint64_t id; /* private guest value, echoed in resp */ |
| blkif_sector_t sector_number;/* start sector idx on disk */ |
| uint64_t nr_sectors; /* number of contiguous sectors to discard*/ |
| }; |
| typedef struct blkif_request_discard blkif_request_discard_t; |
| |
| struct blkif_request_indirect { |
| uint8_t operation; /* BLKIF_OP_INDIRECT */ |
| uint8_t indirect_op; /* BLKIF_OP_{READ/WRITE} */ |
| uint16_t nr_segments; /* number of segments */ |
| uint64_t id; /* private guest value, echoed in resp */ |
| blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */ |
| blkif_vdev_t handle; /* same as for read/write requests */ |
| grant_ref_t indirect_grefs[BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST]; |
| #ifdef __i386__ |
| uint64_t pad; /* Make it 64 byte aligned on i386 */ |
| #endif |
| }; |
| typedef struct blkif_request_indirect blkif_request_indirect_t; |
| |
| struct blkif_response { |
| uint64_t id; /* copied from request */ |
| uint8_t operation; /* copied from request */ |
| int16_t status; /* BLKIF_RSP_??? */ |
| }; |
| typedef struct blkif_response blkif_response_t; |
| |
| /* |
| * STATUS RETURN CODES. |
| */ |
| /* Operation not supported (only happens on barrier writes). */ |
| #define BLKIF_RSP_EOPNOTSUPP -2 |
| /* Operation failed for some unspecified reason (-EIO). */ |
| #define BLKIF_RSP_ERROR -1 |
| /* Operation completed successfully. */ |
| #define BLKIF_RSP_OKAY 0 |
| |
| /* |
| * Generate blkif ring structures and types. |
| */ |
| DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response); |
| |
| #define VDISK_CDROM 0x1 |
| #define VDISK_REMOVABLE 0x2 |
| #define VDISK_READONLY 0x4 |
| |
| #endif /* __XEN_PUBLIC_IO_BLKIF_H__ */ |
| |
| /* |
| * Local variables: |
| * mode: C |
| * c-file-style: "BSD" |
| * c-basic-offset: 4 |
| * tab-width: 4 |
| * indent-tabs-mode: nil |
| * End: |
| */ |
