On 08/20/2014 03:25 PM, Konrad Rzeszutek Wilk wrote:
On Mon, Aug 18, 2014 at 11:31:47AM +0200, jgross@xxxxxxxx wrote:
From: Juergen Gross <jgross@xxxxxxxx>
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 comment
- 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@xxxxxxxx>
---
include/xen/interface/io/vscsiif.h | 214 +++++++++++++++++++++++++++++++++++++
1 file changed, 214 insertions(+)
create mode 100644 include/xen/interface/io/vscsiif.h
diff --git a/include/xen/interface/io/vscsiif.h b/include/xen/interface/io/vscsiif.h
new file mode 100644
index 0000000..4291889
--- /dev/null
+++ b/include/xen/interface/io/vscsiif.h
@@ -0,0 +1,214 @@
+/******************************************************************************
+ * vscsiif.h
+ *
+ * Based on the blkif.h code.
+ *
+ * This interface is to be regarded as a stable API between XEN domains
+ * running potentially different Linux kernel versions.
+ *
+ * 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) FUJITSU Limited 2008.
+ */
+
+#ifndef __XEN__PUBLIC_IO_SCSI_H__
+#define __XEN__PUBLIC_IO_SCSI_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()).
+ */
+
+/*
+ * 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.
+ *
+ * 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.
+ *
+ *****************************************************************************
+ * 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: <uint16_t>
+ * 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: <uint32_t>
+ *
+ * The identifier of the Xen event channel used to signal activity
+ * in the ring buffer.
+ *
+ * ring-ref
+ * Values: <uint32_t>
Should there a bit of explanation here about what 'ring ref' is?
Uuh, yes. I'll add it.
+ *
+ * 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.
+ */
+
+/* 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.
+ */
+#define VSCSIIF_ACT_SCSI_CDB 1
+
+/*
+ * Request abort of a running operation for the specified target given by
+ * channel, id, lun and the operation's rqid in ref_rqid.
+ */
+#define VSCSIIF_ACT_SCSI_ABORT 2
+
+/*
+ * Request a device reset of the specified target (channel and id).
+ */
+#define VSCSIIF_ACT_SCSI_RESET 3
+
+/*
+ * Preset scatter/gather elements for a following request. Deprecated.
+ * Keeping the define only to avoid usage of the value "4" for other actions.
+ */
+#define VSCSIIF_ACT_SCSI_SG_PRESET 4
+
+/*
+ * 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.
That sounds like the indirect descriptors that virtio and xen-block has.
More questions about that below.
+ */
+#define VSCSIIF_SG_TABLESIZE 26
+
+/*
+ * 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.
+ */
+#define VSCSIIF_MAX_COMMAND_SIZE 16
+#define VSCSIIF_SENSE_BUFFERSIZE 96
+
+struct scsiif_request_segment {
+ grant_ref_t gref;
+ uint16_t offset;
+ uint16_t length;
+};
Yeey, 8 byte data structure!
+
+/* 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;
+ 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_FROM_DEVICE(2)
+ DMA_NONE(3) requests */
+ uint8_t nr_segments; /* Number of pieces of scatter-gather */
+#define VSCSIIF_SG_GRANT 0x80 /* flag: SG elements via grant page */
+ /* nr_segments counts grant pages with
+ SG elements
Stop missing. However I am a bit lost. It says that the 'nr_segments' will have the
count of grant pages with SG elements. Does that mean the req.seg[0].gref points
to an page which will have an array of grant references? And each grant reference
will point to a data page? What about the 'offset' and 'length' of them?
Or does it mean that the 'reg.seg[0].gref' points an page that is filled with
'struct scsiif_request_segment' ? If so, where would the could of those
segments be in? In 'nr_segments'? If that is so where does the VSCSIIF_SG_GRANT
go? Won't we collide?
nr_segments (without the VSCSIIF_SG_GRANT bit) always counts the number
of populated seg[] entries. If VSCSIIF_SG_GRANT is set, each seg[] entry
references another array of struct scsiif_request_segment using a grant
ref, offset into the granted page and a length of the array in bytes.
The resulting number of struct scsiif_request_segment is the sum of
seg[0..nr_segments-1].length / sizeof(struct scsiif_request_segment).
+ usable if "feature-sg-grant" set */
+
+ struct scsiif_request_segment seg[VSCSIIF_SG_TABLESIZE];
+ uint32_t reserved[3];
Or is the flag suppose to show up here?
No. There is no guarantee an "old" domU not aware of "feature-sg-grant"
will have set reserved[] to zero.
+};
+
The previous structure had an comment about the size of the structure.
Should it be here as well?
I can add one.
+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__*/
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