[PATCH 0/8] xen/9pfs: introduce the Xen 9pfs backend

[PATCH 0/8] xen/9pfs: introduce the Xen 9pfs backend

[Stefano Stabellini]

Hi all,

This patch series implements a new transport for 9pfs, aimed at Xen
systems.

The transport is based on a traditional Xen frontend and backend drivers
pair. This patch series implements the backend, which typically runs in
Dom0. I sent another series to implement the frontend in Linux
(http://marc.info/?l=linux-kernel&m=148883047125960&w=2).

The backend complies to the Xen transport for 9pfs specification
version 1, available here:

http://xenbits.xen.org/gitweb/?p=xen.git;a=blob_plain;f=docs/misc/9pfs.markdown;hb=HEAD


Stefano Stabellini (8):
      xen: import ring.h from xen
      xen: introduce the header file for the Xen 9pfs transport protocol
      xen/9pfs: introduce Xen 9pfs backend
      xen/9pfs: connect to the frontend
      xen/9pfs: receive requests from the frontend
      xen/9pfs: implement in/out_iov_from_pdu and vmarshal/vunmarshal
      xen/9pfs: send responses back to the frontend
      xen/9pfs: build and register Xen 9pfs backend

 hw/9pfs/Makefile.objs        |   1 +
 hw/9pfs/xen-9p-backend.c     | 403 ++++++++++++++++++++++++++++++++++++++
 hw/9pfs/xen_9pfs.h           |  20 ++
 hw/block/xen_blkif.h         |   2 +-
 hw/usb/xen-usb.c             |   2 +-
 hw/xen/xen_backend.c         |   1 +
 include/hw/xen/io/ring.h     | 455 +++++++++++++++++++++++++++++++++++++++++++
 include/hw/xen/xen_backend.h |   1 +
 8 files changed, 883 insertions(+), 2 deletions(-)
 create mode 100644 hw/9pfs/xen-9p-backend.c
 create mode 100644 hw/9pfs/xen_9pfs.h
 create mode 100644 include/hw/xen/io/ring.h

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[PATCH 1/8] xen: import ring.h from xen

[Stefano Stabellini]

Do not use the ring.h header installed on the system. Instead, import
the header into the QEMU codebase. This avoids problems when QEMU is
built against a Xen version too old to provide all the ring macros.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: anthony.perard@citrix.com
CC: jgross@suse.com
---
NB: The new macros have not been committed to Xen yet. Do not apply this
patch until they do.
---
---
 hw/block/xen_blkif.h     |   2 +-
 hw/usb/xen-usb.c         |   2 +-
 include/hw/xen/io/ring.h | 455 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 457 insertions(+), 2 deletions(-)
 create mode 100644 include/hw/xen/io/ring.h

diff --git a/hw/block/xen_blkif.h b/hw/block/xen_blkif.h
index 3300b6f..3e6e1ea 100644
--- a/hw/block/xen_blkif.h
+++ b/hw/block/xen_blkif.h
@@ -1,7 +1,7 @@
 #ifndef XEN_BLKIF_H
 #define XEN_BLKIF_H
 
-#include <xen/io/ring.h>
+#include "hw/xen/io/ring.h"
 #include <xen/io/blkif.h>
 #include <xen/io/protocols.h>
 
diff --git a/hw/usb/xen-usb.c b/hw/usb/xen-usb.c
index 8e676e6..370b3d9 100644
--- a/hw/usb/xen-usb.c
+++ b/hw/usb/xen-usb.c
@@ -33,7 +33,7 @@
 #include "qapi/qmp/qint.h"
 #include "qapi/qmp/qstring.h"
 
-#include <xen/io/ring.h>
+#include "hw/xen/io/ring.h"
 #include <xen/io/usbif.h>
 
 /*
diff --git a/include/hw/xen/io/ring.h b/include/hw/xen/io/ring.h
new file mode 100644
index 0000000..cf01fc3
--- /dev/null
+++ b/include/hw/xen/io/ring.h
@@ -0,0 +1,455 @@
+/******************************************************************************
+ * ring.h
+ * 
+ * Shared producer-consumer ring macros.
+ *
+ * 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.
+ *
+ * Tim Deegan and Andrew Warfield November 2004.
+ */
+
+#ifndef __XEN_PUBLIC_IO_RING_H__
+#define __XEN_PUBLIC_IO_RING_H__
+
+#if __XEN_INTERFACE_VERSION__ < 0x00030208
+#define xen_mb()  mb()
+#define xen_rmb() rmb()
+#define xen_wmb() wmb()
+#endif
+
+typedef unsigned int RING_IDX;
+
+/* Round a 32-bit unsigned constant down to the nearest power of two. */
+#define __RD2(_x)  (((_x) & 0x00000002) ? 0x2                  : ((_x) & 0x1))
+#define __RD4(_x)  (((_x) & 0x0000000c) ? __RD2((_x)>>2)<<2    : __RD2(_x))
+#define __RD8(_x)  (((_x) & 0x000000f0) ? __RD4((_x)>>4)<<4    : __RD4(_x))
+#define __RD16(_x) (((_x) & 0x0000ff00) ? __RD8((_x)>>8)<<8    : __RD8(_x))
+#define __RD32(_x) (((_x) & 0xffff0000) ? __RD16((_x)>>16)<<16 : __RD16(_x))
+
+/*
+ * Calculate size of a shared ring, given the total available space for the
+ * ring and indexes (_sz), and the name tag of the request/response structure.
+ * A ring contains as many entries as will fit, rounded down to the nearest 
+ * power of two (so we can mask with (size-1) to loop around).
+ */
+#define __CONST_RING_SIZE(_s, _sz) \
+    (__RD32(((_sz) - offsetof(struct _s##_sring, ring)) / \
+	    sizeof(((struct _s##_sring *)0)->ring[0])))
+/*
+ * The same for passing in an actual pointer instead of a name tag.
+ */
+#define __RING_SIZE(_s, _sz) \
+    (__RD32(((_sz) - (long)(_s)->ring + (long)(_s)) / sizeof((_s)->ring[0])))
+
+/*
+ * Macros to make the correct C datatypes for a new kind of ring.
+ * 
+ * To make a new ring datatype, you need to have two message structures,
+ * let's say request_t, and response_t already defined.
+ *
+ * In a header where you want the ring datatype declared, you then do:
+ *
+ *     DEFINE_RING_TYPES(mytag, request_t, response_t);
+ *
+ * These expand out to give you a set of types, as you can see below.
+ * The most important of these are:
+ * 
+ *     mytag_sring_t      - The shared ring.
+ *     mytag_front_ring_t - The 'front' half of the ring.
+ *     mytag_back_ring_t  - The 'back' half of the ring.
+ *
+ * To initialize a ring in your code you need to know the location and size
+ * of the shared memory area (PAGE_SIZE, for instance). To initialise
+ * the front half:
+ *
+ *     mytag_front_ring_t front_ring;
+ *     SHARED_RING_INIT((mytag_sring_t *)shared_page);
+ *     FRONT_RING_INIT(&front_ring, (mytag_sring_t *)shared_page, PAGE_SIZE);
+ *
+ * Initializing the back follows similarly (note that only the front
+ * initializes the shared ring):
+ *
+ *     mytag_back_ring_t back_ring;
+ *     BACK_RING_INIT(&back_ring, (mytag_sring_t *)shared_page, PAGE_SIZE);
+ */
+
+#define DEFINE_RING_TYPES(__name, __req_t, __rsp_t)                     \
+                                                                        \
+/* Shared ring entry */                                                 \
+union __name##_sring_entry {                                            \
+    __req_t req;                                                        \
+    __rsp_t rsp;                                                        \
+};                                                                      \
+                                                                        \
+/* Shared ring page */                                                  \
+struct __name##_sring {                                                 \
+    RING_IDX req_prod, req_event;                                       \
+    RING_IDX rsp_prod, rsp_event;                                       \
+    union {                                                             \
+        struct {                                                        \
+            uint8_t smartpoll_active;                                   \
+        } netif;                                                        \
+        struct {                                                        \
+            uint8_t msg;                                                \
+        } tapif_user;                                                   \
+        uint8_t pvt_pad[4];                                             \
+    } pvt;                                                              \
+    uint8_t __pad[44];                                                  \
+    union __name##_sring_entry ring[1]; /* variable-length */           \
+};                                                                      \
+                                                                        \
+/* "Front" end's private variables */                                   \
+struct __name##_front_ring {                                            \
+    RING_IDX req_prod_pvt;                                              \
+    RING_IDX rsp_cons;                                                  \
+    unsigned int nr_ents;                                               \
+    struct __name##_sring *sring;                                       \
+};                                                                      \
+                                                                        \
+/* "Back" end's private variables */                                    \
+struct __name##_back_ring {                                             \
+    RING_IDX rsp_prod_pvt;                                              \
+    RING_IDX req_cons;                                                  \
+    unsigned int nr_ents;                                               \
+    struct __name##_sring *sring;                                       \
+};                                                                      \
+                                                                        \
+/* Syntactic sugar */                                                   \
+typedef struct __name##_sring __name##_sring_t;                         \
+typedef struct __name##_front_ring __name##_front_ring_t;               \
+typedef struct __name##_back_ring __name##_back_ring_t
+
+/*
+ * Macros for manipulating rings.
+ * 
+ * FRONT_RING_whatever works on the "front end" of a ring: here 
+ * requests are pushed on to the ring and responses taken off it.
+ * 
+ * BACK_RING_whatever works on the "back end" of a ring: here 
+ * requests are taken off the ring and responses put on.
+ * 
+ * N.B. these macros do NO INTERLOCKS OR FLOW CONTROL. 
+ * This is OK in 1-for-1 request-response situations where the 
+ * requestor (front end) never has more than RING_SIZE()-1
+ * outstanding requests.
+ */
+
+/* Initialising empty rings */
+#define SHARED_RING_INIT(_s) do {                                       \
+    (_s)->req_prod  = (_s)->rsp_prod  = 0;                              \
+    (_s)->req_event = (_s)->rsp_event = 1;                              \
+    (void)memset((_s)->pvt.pvt_pad, 0, sizeof((_s)->pvt.pvt_pad));      \
+    (void)memset((_s)->__pad, 0, sizeof((_s)->__pad));                  \
+} while(0)
+
+#define FRONT_RING_INIT(_r, _s, __size) do {                            \
+    (_r)->req_prod_pvt = 0;                                             \
+    (_r)->rsp_cons = 0;                                                 \
+    (_r)->nr_ents = __RING_SIZE(_s, __size);                            \
+    (_r)->sring = (_s);                                                 \
+} while (0)
+
+#define BACK_RING_INIT(_r, _s, __size) do {                             \
+    (_r)->rsp_prod_pvt = 0;                                             \
+    (_r)->req_cons = 0;                                                 \
+    (_r)->nr_ents = __RING_SIZE(_s, __size);                            \
+    (_r)->sring = (_s);                                                 \
+} while (0)
+
+/* How big is this ring? */
+#define RING_SIZE(_r)                                                   \
+    ((_r)->nr_ents)
+
+/* Number of free requests (for use on front side only). */
+#define RING_FREE_REQUESTS(_r)                                          \
+    (RING_SIZE(_r) - ((_r)->req_prod_pvt - (_r)->rsp_cons))
+
+/* Test if there is an empty slot available on the front ring.
+ * (This is only meaningful from the front. )
+ */
+#define RING_FULL(_r)                                                   \
+    (RING_FREE_REQUESTS(_r) == 0)
+
+/* Test if there are outstanding messages to be processed on a ring. */
+#define RING_HAS_UNCONSUMED_RESPONSES(_r)                               \
+    ((_r)->sring->rsp_prod - (_r)->rsp_cons)
+
+#ifdef __GNUC__
+#define RING_HAS_UNCONSUMED_REQUESTS(_r) ({                             \
+    unsigned int req = (_r)->sring->req_prod - (_r)->req_cons;          \
+    unsigned int rsp = RING_SIZE(_r) -                                  \
+        ((_r)->req_cons - (_r)->rsp_prod_pvt);                          \
+    req < rsp ? req : rsp;                                              \
+})
+#else
+/* Same as above, but without the nice GCC ({ ... }) syntax. */
+#define RING_HAS_UNCONSUMED_REQUESTS(_r)                                \
+    ((((_r)->sring->req_prod - (_r)->req_cons) <                        \
+      (RING_SIZE(_r) - ((_r)->req_cons - (_r)->rsp_prod_pvt))) ?        \
+     ((_r)->sring->req_prod - (_r)->req_cons) :                         \
+     (RING_SIZE(_r) - ((_r)->req_cons - (_r)->rsp_prod_pvt)))
+#endif
+
+/* Direct access to individual ring elements, by index. */
+#define RING_GET_REQUEST(_r, _idx)                                      \
+    (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].req))
+
+/*
+ * Get a local copy of a request.
+ *
+ * Use this in preference to RING_GET_REQUEST() so all processing is
+ * done on a local copy that cannot be modified by the other end.
+ *
+ * Note that https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 may cause this
+ * to be ineffective where _req is a struct which consists of only bitfields.
+ */
+#define RING_COPY_REQUEST(_r, _idx, _req) do {				\
+	/* Use volatile to force the copy into _req. */			\
+	*(_req) = *(volatile typeof(_req))RING_GET_REQUEST(_r, _idx);	\
+} while (0)
+
+#define RING_GET_RESPONSE(_r, _idx)                                     \
+    (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].rsp))
+
+/* Loop termination condition: Would the specified index overflow the ring? */
+#define RING_REQUEST_CONS_OVERFLOW(_r, _cons)                           \
+    (((_cons) - (_r)->rsp_prod_pvt) >= RING_SIZE(_r))
+
+/* Ill-behaved frontend determination: Can there be this many requests? */
+#define RING_REQUEST_PROD_OVERFLOW(_r, _prod)                           \
+    (((_prod) - (_r)->rsp_prod_pvt) > RING_SIZE(_r))
+
+#define RING_PUSH_REQUESTS(_r) do {                                     \
+    xen_wmb(); /* back sees requests /before/ updated producer index */ \
+    (_r)->sring->req_prod = (_r)->req_prod_pvt;                         \
+} while (0)
+
+#define RING_PUSH_RESPONSES(_r) do {                                    \
+    xen_wmb(); /* front sees resps /before/ updated producer index */   \
+    (_r)->sring->rsp_prod = (_r)->rsp_prod_pvt;                         \
+} while (0)
+
+/*
+ * Notification hold-off (req_event and rsp_event):
+ * 
+ * When queueing requests or responses on a shared ring, it may not always be
+ * necessary to notify the remote end. For example, if requests are in flight
+ * in a backend, the front may be able to queue further requests without
+ * notifying the back (if the back checks for new requests when it queues
+ * responses).
+ * 
+ * When enqueuing requests or responses:
+ * 
+ *  Use RING_PUSH_{REQUESTS,RESPONSES}_AND_CHECK_NOTIFY(). The second argument
+ *  is a boolean return value. True indicates that the receiver requires an
+ *  asynchronous notification.
+ * 
+ * After dequeuing requests or responses (before sleeping the connection):
+ * 
+ *  Use RING_FINAL_CHECK_FOR_REQUESTS() or RING_FINAL_CHECK_FOR_RESPONSES().
+ *  The second argument is a boolean return value. True indicates that there
+ *  are pending messages on the ring (i.e., the connection should not be put
+ *  to sleep).
+ * 
+ *  These macros will set the req_event/rsp_event field to trigger a
+ *  notification on the very next message that is enqueued. If you want to
+ *  create batches of work (i.e., only receive a notification after several
+ *  messages have been enqueued) then you will need to create a customised
+ *  version of the FINAL_CHECK macro in your own code, which sets the event
+ *  field appropriately.
+ */
+
+#define RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(_r, _notify) do {           \
+    RING_IDX __old = (_r)->sring->req_prod;                             \
+    RING_IDX __new = (_r)->req_prod_pvt;                                \
+    xen_wmb(); /* back sees requests /before/ updated producer index */ \
+    (_r)->sring->req_prod = __new;                                      \
+    xen_mb(); /* back sees new requests /before/ we check req_event */  \
+    (_notify) = ((RING_IDX)(__new - (_r)->sring->req_event) <           \
+                 (RING_IDX)(__new - __old));                            \
+} while (0)
+
+#define RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(_r, _notify) do {          \
+    RING_IDX __old = (_r)->sring->rsp_prod;                             \
+    RING_IDX __new = (_r)->rsp_prod_pvt;                                \
+    xen_wmb(); /* front sees resps /before/ updated producer index */   \
+    (_r)->sring->rsp_prod = __new;                                      \
+    xen_mb(); /* front sees new resps /before/ we check rsp_event */    \
+    (_notify) = ((RING_IDX)(__new - (_r)->sring->rsp_event) <           \
+                 (RING_IDX)(__new - __old));                            \
+} while (0)
+
+#define RING_FINAL_CHECK_FOR_REQUESTS(_r, _work_to_do) do {             \
+    (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r);                   \
+    if (_work_to_do) break;                                             \
+    (_r)->sring->req_event = (_r)->req_cons + 1;                        \
+    xen_mb();                                                           \
+    (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r);                   \
+} while (0)
+
+#define RING_FINAL_CHECK_FOR_RESPONSES(_r, _work_to_do) do {            \
+    (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r);                  \
+    if (_work_to_do) break;                                             \
+    (_r)->sring->rsp_event = (_r)->rsp_cons + 1;                        \
+    xen_mb();                                                           \
+    (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r);                  \
+} while (0)
+
+
+/*
+ * DEFINE_XEN_FLEX_RING_AND_INTF defines two monodirectional rings and
+ * functions to check if there is data on the ring, and to read and
+ * write to them.
+ *
+ * DEFINE_XEN_FLEX_RING is similar to DEFINE_XEN_FLEX_RING_AND_INTF, but
+ * does not define the indexes page. As different protocols can have
+ * extensions to the basic format, this macro allow them to define their
+ * own struct.
+ *
+ * XEN_FLEX_RING_SIZE
+ *   Convenience macro to calculate the size of one of the two rings
+ *   from the overall order.
+ *
+ * $NAME_mask
+ *   Function to apply the size mask to an index, to reduce the index
+ *   within the range [0-size].
+ *
+ * $NAME_read_packet
+ *   Function to read data from the ring. The amount of data to read is
+ *   specified by the "size" argument.
+ *
+ * $NAME_write_packet
+ *   Function to write data to the ring. The amount of data to write is
+ *   specified by the "size" argument.
+ *
+ * $NAME_get_ring_ptr
+ *   Convenience function that returns a pointer to read/write to the
+ *   ring at the right location.
+ *
+ * $NAME_data_intf
+ *   Indexes page, shared between frontend and backend. It also
+ *   contains the array of grant refs.
+ *
+ * $NAME_queued
+ *   Function to calculate how many bytes are currently on the ring,
+ *   ready to be read. It can also be used to calculate how much free
+ *   space is currently on the ring (ring_size - $NAME_queued()).
+ */
+#define XEN_FLEX_RING_SIZE(order)                                             \
+    (1UL << (order + PAGE_SHIFT - 1))
+
+#define DEFINE_XEN_FLEX_RING_AND_INTF(name)                                   \
+struct name##_data_intf {                                                     \
+    RING_IDX in_cons, in_prod;                                                \
+                                                                              \
+    uint8_t pad1[56];                                                         \
+                                                                              \
+    RING_IDX out_cons, out_prod;                                              \
+                                                                              \
+    uint8_t pad2[56];                                                         \
+                                                                              \
+    RING_IDX ring_order;                                                      \
+    grant_ref_t ref[];                                                        \
+};                                                                            \
+DEFINE_XEN_FLEX_RING(name);
+
+#define DEFINE_XEN_FLEX_RING(name)                                            \
+static inline RING_IDX name##_mask(RING_IDX idx, RING_IDX ring_size)          \
+{                                                                             \
+    return (idx & (ring_size - 1));                                           \
+}                                                                             \
+                                                                              \
+static inline RING_IDX name##_mask_order(RING_IDX idx, RING_IDX ring_order)   \
+{                                                                             \
+    return (idx & (XEN_FLEX_RING_SIZE(ring_order) - 1));                      \
+}                                                                             \
+                                                                              \
+static inline unsigned char* name##_get_ring_ptr(unsigned char *buf,          \
+                                                 RING_IDX idx,                \
+                                                 RING_IDX ring_order)         \
+{                                                                             \
+    return buf + name##_mask_order(idx, ring_order);                          \
+}                                                                             \
+                                                                              \
+static inline void name##_read_packet(const unsigned char *buf,               \
+        RING_IDX masked_prod, RING_IDX *masked_cons,                          \
+        RING_IDX ring_size, void *opaque, size_t size) {                      \
+    if (*masked_cons < masked_prod ||                                         \
+            size <= ring_size - *masked_cons) {                               \
+        memcpy(opaque, buf + *masked_cons, size);                             \
+    } else {                                                                  \
+        memcpy(opaque, buf + *masked_cons, ring_size - *masked_cons);         \
+        memcpy((unsigned char *)opaque + ring_size - *masked_cons, buf,       \
+                size - (ring_size - *masked_cons));                           \
+    }                                                                         \
+    *masked_cons = name##_mask(*masked_cons + size, ring_size);               \
+}                                                                             \
+                                                                              \
+static inline void name##_write_packet(unsigned char *buf,                    \
+        RING_IDX *masked_prod, RING_IDX masked_cons,                          \
+        RING_IDX ring_size, const void *opaque, size_t size) {                \
+    if (*masked_prod < masked_cons ||                                         \
+        size <= ring_size - *masked_prod) {                                   \
+        memcpy(buf + *masked_prod, opaque, size);                             \
+    } else {                                                                  \
+        memcpy(buf + *masked_prod, opaque, ring_size - *masked_prod);         \
+        memcpy(buf, (unsigned char *)opaque + (ring_size - *masked_prod),     \
+                size - (ring_size - *masked_prod));                           \
+    }                                                                         \
+    *masked_prod = name##_mask(*masked_prod + size, ring_size);               \
+}                                                                             \
+                                                                              \
+struct name##_data {                                                          \
+    unsigned char *in; /* half of the allocation */                           \
+    unsigned char *out; /* half of the allocation */                          \
+};                                                                            \
+                                                                              \
+                                                                              \
+static inline RING_IDX name##_queued(RING_IDX prod,                           \
+        RING_IDX cons, RING_IDX ring_size)                                    \
+{                                                                             \
+    RING_IDX size;                                                            \
+                                                                              \
+    if (prod == cons)                                                         \
+        return 0;                                                             \
+                                                                              \
+    prod = name##_mask(prod, ring_size);                                      \
+    cons = name##_mask(cons, ring_size);                                      \
+                                                                              \
+    if (prod == cons)                                                         \
+        return ring_size;                                                     \
+                                                                              \
+    if (prod > cons)                                                          \
+        size = prod - cons;                                                   \
+    else                                                                      \
+        size = ring_size - (cons - prod);                                     \
+    return size;                                                              \
+};
+
+#endif /* __XEN_PUBLIC_IO_RING_H__ */
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
-- 
1.9.1


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[PATCH 2/8] xen: introduce the header file for the Xen 9pfs transport protocol

[Stefano Stabellini]

It uses the new ring.h macros to declare rings and interfaces.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: anthony.perard@citrix.com
CC: jgross@suse.com
---
 hw/9pfs/xen_9pfs.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
 create mode 100644 hw/9pfs/xen_9pfs.h

diff --git a/hw/9pfs/xen_9pfs.h b/hw/9pfs/xen_9pfs.h
new file mode 100644
index 0000000..c4e8901
--- /dev/null
+++ b/hw/9pfs/xen_9pfs.h
@@ -0,0 +1,20 @@
+#ifndef XEN_9PFS_H
+#define XEN_9PFS_H
+
+#include "hw/xen/io/ring.h"
+#include <xen/io/protocols.h>
+
+struct xen_9pfs_header {
+	uint32_t size;
+	uint8_t id;
+	uint16_t tag;
+
+	/* uint8_t sdata[]; */
+} __attribute__((packed));
+
+#define PAGE_SHIFT XC_PAGE_SHIFT
+#define XEN_9PFS_RING_ORDER 6
+#define XEN_9PFS_RING_SIZE  XEN_FLEX_RING_SIZE(XEN_9PFS_RING_ORDER)
+DEFINE_XEN_FLEX_RING_AND_INTF(xen_9pfs);
+
+#endif
-- 
1.9.1


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[PATCH 3/8] xen/9pfs: introduce Xen 9pfs backend

[Stefano Stabellini]

Introduce the Xen 9pfs backend: add struct XenDevOps to register as a
Xen backend and add struct V9fsTransport to register as v9fs transport.

All functions are empty stubs for now.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: anthony.perard@citrix.com
CC: jgross@suse.com
CC: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
CC: Greg Kurz <groug@kaod.org>
---
 hw/9pfs/xen-9p-backend.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 hw/9pfs/xen-9p-backend.c

diff --git a/hw/9pfs/xen-9p-backend.c b/hw/9pfs/xen-9p-backend.c
new file mode 100644
index 0000000..924fb64
--- /dev/null
+++ b/hw/9pfs/xen-9p-backend.c
@@ -0,0 +1,96 @@
+/*
+ * Xen 9p backend
+ *
+ * Copyright Aporeto 2017
+ *
+ * Authors:
+ *  Stefano Stabellini <stefano@aporeto.com>
+ *
+ */
+
+#include "qemu/osdep.h"
+
+#include "hw/hw.h"
+#include "hw/9pfs/9p.h"
+#include "hw/xen/xen_backend.h"
+#include "xen_9pfs.h"
+#include "qemu/config-file.h"
+#include "fsdev/qemu-fsdev.h"
+
+struct Xen9pfsDev {
+    struct XenDevice xendev;  /* must be first */
+};
+
+static ssize_t xen_9pfs_pdu_vmarshal(V9fsPDU *pdu,
+                                     size_t offset,
+                                     const char *fmt,
+                                     va_list ap)
+{
+    return 0;
+}
+
+static ssize_t xen_9pfs_pdu_vunmarshal(V9fsPDU *pdu,
+                                       size_t offset,
+                                       const char *fmt,
+                                       va_list ap)
+{
+    return 0;
+}
+
+static void xen_9pfs_init_out_iov_from_pdu(V9fsPDU *pdu,
+                                           struct iovec **piov,
+                                           unsigned int *pniov)
+{
+}
+
+static void xen_9pfs_init_in_iov_from_pdu(V9fsPDU *pdu,
+                                          struct iovec **piov,
+                                          unsigned int *pniov,
+                                          size_t size)
+{
+}
+
+static void xen_9pfs_push_and_notify(V9fsPDU *pdu)
+{
+}
+
+static const struct V9fsTransport xen_9p_transport = {
+    .pdu_vmarshal = xen_9pfs_pdu_vmarshal,
+    .pdu_vunmarshal = xen_9pfs_pdu_vunmarshal,
+    .init_in_iov_from_pdu = xen_9pfs_init_in_iov_from_pdu,
+    .init_out_iov_from_pdu = xen_9pfs_init_out_iov_from_pdu,
+    .push_and_notify = xen_9pfs_push_and_notify,
+};
+
+static int xen_9pfs_init(struct XenDevice *xendev)
+{
+    return 0;
+}
+
+static int xen_9pfs_free(struct XenDevice *xendev)
+{
+    return -1;
+}
+
+static int xen_9pfs_connect(struct XenDevice *xendev)
+{
+    return 0;
+}
+
+static void xen_9pfs_alloc(struct XenDevice *xendev)
+{
+}
+
+static void xen_9pfs_disconnect(struct XenDevice *xendev)
+{
+}
+
+struct XenDevOps xen_9pfs_ops = {
+    .size       = sizeof(struct Xen9pfsDev),
+    .flags      = DEVOPS_FLAG_NEED_GNTDEV,
+    .alloc      = xen_9pfs_alloc,
+    .init       = xen_9pfs_init,
+    .initialise    = xen_9pfs_connect,
+    .disconnect = xen_9pfs_disconnect,
+    .free       = xen_9pfs_free,
+};
-- 
1.9.1


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Re: [PATCH 3/8] xen/9pfs: introduce Xen 9pfs backend

[Greg Kurz]

[-- Attachment #1.1: Type: text/plain, Size: 3776 bytes --]

On Mon,  6 Mar 2017 18:12:43 -0800
Stefano Stabellini <sstabellini@kernel.org> wrote:

> Introduce the Xen 9pfs backend: add struct XenDevOps to register as a
> Xen backend and add struct V9fsTransport to register as v9fs transport.
> 
> All functions are empty stubs for now.
> 
> Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
> CC: anthony.perard@citrix.com
> CC: jgross@suse.com
> CC: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> CC: Greg Kurz <groug@kaod.org>
> ---
>  hw/9pfs/xen-9p-backend.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 96 insertions(+)
>  create mode 100644 hw/9pfs/xen-9p-backend.c
> 
> diff --git a/hw/9pfs/xen-9p-backend.c b/hw/9pfs/xen-9p-backend.c
> new file mode 100644
> index 0000000..924fb64
> --- /dev/null
> +++ b/hw/9pfs/xen-9p-backend.c
> @@ -0,0 +1,96 @@
> +/*
> + * Xen 9p backend
> + *
> + * Copyright Aporeto 2017
> + *
> + * Authors:
> + *  Stefano Stabellini <stefano@aporeto.com>
> + *
> + */
> +
> +#include "qemu/osdep.h"
> +
> +#include "hw/hw.h"
> +#include "hw/9pfs/9p.h"
> +#include "hw/xen/xen_backend.h"
> +#include "xen_9pfs.h"
> +#include "qemu/config-file.h"
> +#include "fsdev/qemu-fsdev.h"
> +
> +struct Xen9pfsDev {
> +    struct XenDevice xendev;  /* must be first */
> +};

According to HACKING, this should be:

typedef struct Xen9pfsDev {
    struct XenDevice xendev;  /* must be first */
} Xen9pfsDev;

and...

> +
> +static ssize_t xen_9pfs_pdu_vmarshal(V9fsPDU *pdu,
> +                                     size_t offset,
> +                                     const char *fmt,
> +                                     va_list ap)
> +{
> +    return 0;
> +}
> +
> +static ssize_t xen_9pfs_pdu_vunmarshal(V9fsPDU *pdu,
> +                                       size_t offset,
> +                                       const char *fmt,
> +                                       va_list ap)
> +{
> +    return 0;
> +}
> +
> +static void xen_9pfs_init_out_iov_from_pdu(V9fsPDU *pdu,
> +                                           struct iovec **piov,
> +                                           unsigned int *pniov)
> +{
> +}
> +
> +static void xen_9pfs_init_in_iov_from_pdu(V9fsPDU *pdu,
> +                                          struct iovec **piov,
> +                                          unsigned int *pniov,
> +                                          size_t size)
> +{
> +}
> +
> +static void xen_9pfs_push_and_notify(V9fsPDU *pdu)
> +{
> +}
> +
> +static const struct V9fsTransport xen_9p_transport = {
> +    .pdu_vmarshal = xen_9pfs_pdu_vmarshal,
> +    .pdu_vunmarshal = xen_9pfs_pdu_vunmarshal,
> +    .init_in_iov_from_pdu = xen_9pfs_init_in_iov_from_pdu,
> +    .init_out_iov_from_pdu = xen_9pfs_init_out_iov_from_pdu,
> +    .push_and_notify = xen_9pfs_push_and_notify,
> +};
> +
> +static int xen_9pfs_init(struct XenDevice *xendev)
> +{
> +    return 0;
> +}
> +
> +static int xen_9pfs_free(struct XenDevice *xendev)
> +{
> +    return -1;
> +}
> +
> +static int xen_9pfs_connect(struct XenDevice *xendev)
> +{
> +    return 0;
> +}
> +
> +static void xen_9pfs_alloc(struct XenDevice *xendev)
> +{
> +}
> +
> +static void xen_9pfs_disconnect(struct XenDevice *xendev)
> +{
> +}
> +
> +struct XenDevOps xen_9pfs_ops = {
> +    .size       = sizeof(struct Xen9pfsDev),

... s/struct //

> +    .flags      = DEVOPS_FLAG_NEED_GNTDEV,
> +    .alloc      = xen_9pfs_alloc,
> +    .init       = xen_9pfs_init,
> +    .initialise    = xen_9pfs_connect,
> +    .disconnect = xen_9pfs_disconnect,
> +    .free       = xen_9pfs_free,
> +};

With the above comments addressed:

Reviewed-by: Greg Kurz <groug@kaod.org>

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Re: [PATCH 3/8] xen/9pfs: introduce Xen 9pfs backend

[Greg Kurz]

[-- Attachment #1.1: Type: text/plain, Size: 5239 bytes --]

On Thu, 9 Mar 2017 18:54:26 +0100
Greg Kurz <groug@kaod.org> wrote:

> On Mon,  6 Mar 2017 18:12:43 -0800
> Stefano Stabellini <sstabellini@kernel.org> wrote:
> 
> > Introduce the Xen 9pfs backend: add struct XenDevOps to register as a
> > Xen backend and add struct V9fsTransport to register as v9fs transport.
> > 
> > All functions are empty stubs for now.
> > 
> > Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
> > CC: anthony.perard@citrix.com
> > CC: jgross@suse.com
> > CC: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> > CC: Greg Kurz <groug@kaod.org>
> > ---
> >  hw/9pfs/xen-9p-backend.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 96 insertions(+)
> >  create mode 100644 hw/9pfs/xen-9p-backend.c
> > 
> > diff --git a/hw/9pfs/xen-9p-backend.c b/hw/9pfs/xen-9p-backend.c
> > new file mode 100644
> > index 0000000..924fb64
> > --- /dev/null
> > +++ b/hw/9pfs/xen-9p-backend.c
> > @@ -0,0 +1,96 @@
> > +/*
> > + * Xen 9p backend
> > + *
> > + * Copyright Aporeto 2017
> > + *
> > + * Authors:
> > + *  Stefano Stabellini <stefano@aporeto.com>
> > + *
> > + */
> > +
> > +#include "qemu/osdep.h"
> > +
> > +#include "hw/hw.h"
> > +#include "hw/9pfs/9p.h"
> > +#include "hw/xen/xen_backend.h"
> > +#include "xen_9pfs.h"
> > +#include "qemu/config-file.h"
> > +#include "fsdev/qemu-fsdev.h"
> > +
> > +struct Xen9pfsDev {
> > +    struct XenDevice xendev;  /* must be first */
> > +};  
> 
> According to HACKING, this should be:
> 
> typedef struct Xen9pfsDev {
>     struct XenDevice xendev;  /* must be first */
> } Xen9pfsDev;
> 
> and...
> 
> > +
> > +static ssize_t xen_9pfs_pdu_vmarshal(V9fsPDU *pdu,
> > +                                     size_t offset,
> > +                                     const char *fmt,
> > +                                     va_list ap)
> > +{
> > +    return 0;
> > +}
> > +
> > +static ssize_t xen_9pfs_pdu_vunmarshal(V9fsPDU *pdu,
> > +                                       size_t offset,
> > +                                       const char *fmt,
> > +                                       va_list ap)
> > +{
> > +    return 0;
> > +}
> > +
> > +static void xen_9pfs_init_out_iov_from_pdu(V9fsPDU *pdu,
> > +                                           struct iovec **piov,
> > +                                           unsigned int *pniov)
> > +{
> > +}
> > +
> > +static void xen_9pfs_init_in_iov_from_pdu(V9fsPDU *pdu,
> > +                                          struct iovec **piov,
> > +                                          unsigned int *pniov,
> > +                                          size_t size)
> > +{
> > +}
> > +
> > +static void xen_9pfs_push_and_notify(V9fsPDU *pdu)
> > +{
> > +}
> > +
> > +static const struct V9fsTransport xen_9p_transport = {
> > +    .pdu_vmarshal = xen_9pfs_pdu_vmarshal,
> > +    .pdu_vunmarshal = xen_9pfs_pdu_vunmarshal,
> > +    .init_in_iov_from_pdu = xen_9pfs_init_in_iov_from_pdu,
> > +    .init_out_iov_from_pdu = xen_9pfs_init_out_iov_from_pdu,
> > +    .push_and_notify = xen_9pfs_push_and_notify,
> > +};
> > +
> > +static int xen_9pfs_init(struct XenDevice *xendev)
> > +{
> > +    return 0;
> > +}
> > +
> > +static int xen_9pfs_free(struct XenDevice *xendev)
> > +{
> > +    return -1;
> > +}
> > +
> > +static int xen_9pfs_connect(struct XenDevice *xendev)
> > +{
> > +    return 0;
> > +}
> > +
> > +static void xen_9pfs_alloc(struct XenDevice *xendev)
> > +{
> > +}
> > +
> > +static void xen_9pfs_disconnect(struct XenDevice *xendev)
> > +{
> > +}
> > +
> > +struct XenDevOps xen_9pfs_ops = {
> > +    .size       = sizeof(struct Xen9pfsDev),  
> 
> ... s/struct //
> 
> > +    .flags      = DEVOPS_FLAG_NEED_GNTDEV,
> > +    .alloc      = xen_9pfs_alloc,
> > +    .init       = xen_9pfs_init,
> > +    .initialise    = xen_9pfs_connect,
> > +    .disconnect = xen_9pfs_disconnect,
> > +    .free       = xen_9pfs_free,
> > +};  
> 
> With the above comments addressed:
> 
> Reviewed-by: Greg Kurz <groug@kaod.org>

Hmm... there's still a problem actually. This patch breaks build for some
targets with '--enable-xen --enable-virtfs':

  LINK    cris-softmmu/qemu-system-cris
../hw/xen/xen_backend.o: In function `xen_be_register_common':
/home/greg/Work/qemu/qemu-9p/hw/xen/xen_backend.c:588: undefined reference to `xen_9pfs_ops'

This happens because only targets that support virtio and PCI pull the
9pfs/fsdev object files. This is an effort to have smaller QEMU binaries,
based on the historical dependency of 9pfs on virtio. This patch breaks
this assumption if CONFIG_XEN_BACKEND is defined but the target doesn't
define CONFIG_VIRTIO and CONFIG_PCI.

Since 9pfs can now be used with another transport, I guess that the
dependency on virtio and PCI isn't right anymore. The new condition
for targets to support 9pfs should rather be something like:

CONFIG_VIRTFS == y && CONFIG_SOFTMMU == y && (CONFIG_VIRTIO == y || CONFIG_XEN_BACKEND == y)

This would cause all targets to pull the 9pfs/fsdev object files though.

So I have a question: do all targets need to support the Xen backend, really ?

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Re: [Qemu-devel] [PATCH 3/8] xen/9pfs: introduce Xen 9pfs backend

[Stefano Stabellini]

On Fri, 10 Mar 2017, Greg Kurz wrote:
> On Thu, 9 Mar 2017 18:54:26 +0100
> Greg Kurz <groug@kaod.org> wrote:
> 
> > On Mon,  6 Mar 2017 18:12:43 -0800
> > Stefano Stabellini <sstabellini@kernel.org> wrote:
> > 
> > > Introduce the Xen 9pfs backend: add struct XenDevOps to register as a
> > > Xen backend and add struct V9fsTransport to register as v9fs transport.
> > > 
> > > All functions are empty stubs for now.
> > > 
> > > Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
> > > CC: anthony.perard@citrix.com
> > > CC: jgross@suse.com
> > > CC: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> > > CC: Greg Kurz <groug@kaod.org>
> > > ---
> > >  hw/9pfs/xen-9p-backend.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++++
> > >  1 file changed, 96 insertions(+)
> > >  create mode 100644 hw/9pfs/xen-9p-backend.c
> > > 
> > > diff --git a/hw/9pfs/xen-9p-backend.c b/hw/9pfs/xen-9p-backend.c
> > > new file mode 100644
> > > index 0000000..924fb64
> > > --- /dev/null
> > > +++ b/hw/9pfs/xen-9p-backend.c
> > > @@ -0,0 +1,96 @@
> > > +/*
> > > + * Xen 9p backend
> > > + *
> > > + * Copyright Aporeto 2017
> > > + *
> > > + * Authors:
> > > + *  Stefano Stabellini <stefano@aporeto.com>
> > > + *
> > > + */
> > > +
> > > +#include "qemu/osdep.h"
> > > +
> > > +#include "hw/hw.h"
> > > +#include "hw/9pfs/9p.h"
> > > +#include "hw/xen/xen_backend.h"
> > > +#include "xen_9pfs.h"
> > > +#include "qemu/config-file.h"
> > > +#include "fsdev/qemu-fsdev.h"
> > > +
> > > +struct Xen9pfsDev {
> > > +    struct XenDevice xendev;  /* must be first */
> > > +};  
> > 
> > According to HACKING, this should be:
> > 
> > typedef struct Xen9pfsDev {
> >     struct XenDevice xendev;  /* must be first */
> > } Xen9pfsDev;
> > 
> > and...
> > 
> > > +
> > > +static ssize_t xen_9pfs_pdu_vmarshal(V9fsPDU *pdu,
> > > +                                     size_t offset,
> > > +                                     const char *fmt,
> > > +                                     va_list ap)
> > > +{
> > > +    return 0;
> > > +}
> > > +
> > > +static ssize_t xen_9pfs_pdu_vunmarshal(V9fsPDU *pdu,
> > > +                                       size_t offset,
> > > +                                       const char *fmt,
> > > +                                       va_list ap)
> > > +{
> > > +    return 0;
> > > +}
> > > +
> > > +static void xen_9pfs_init_out_iov_from_pdu(V9fsPDU *pdu,
> > > +                                           struct iovec **piov,
> > > +                                           unsigned int *pniov)
> > > +{
> > > +}
> > > +
> > > +static void xen_9pfs_init_in_iov_from_pdu(V9fsPDU *pdu,
> > > +                                          struct iovec **piov,
> > > +                                          unsigned int *pniov,
> > > +                                          size_t size)
> > > +{
> > > +}
> > > +
> > > +static void xen_9pfs_push_and_notify(V9fsPDU *pdu)
> > > +{
> > > +}
> > > +
> > > +static const struct V9fsTransport xen_9p_transport = {
> > > +    .pdu_vmarshal = xen_9pfs_pdu_vmarshal,
> > > +    .pdu_vunmarshal = xen_9pfs_pdu_vunmarshal,
> > > +    .init_in_iov_from_pdu = xen_9pfs_init_in_iov_from_pdu,
> > > +    .init_out_iov_from_pdu = xen_9pfs_init_out_iov_from_pdu,
> > > +    .push_and_notify = xen_9pfs_push_and_notify,
> > > +};
> > > +
> > > +static int xen_9pfs_init(struct XenDevice *xendev)
> > > +{
> > > +    return 0;
> > > +}
> > > +
> > > +static int xen_9pfs_free(struct XenDevice *xendev)
> > > +{
> > > +    return -1;
> > > +}
> > > +
> > > +static int xen_9pfs_connect(struct XenDevice *xendev)
> > > +{
> > > +    return 0;
> > > +}
> > > +
> > > +static void xen_9pfs_alloc(struct XenDevice *xendev)
> > > +{
> > > +}
> > > +
> > > +static void xen_9pfs_disconnect(struct XenDevice *xendev)
> > > +{
> > > +}
> > > +
> > > +struct XenDevOps xen_9pfs_ops = {
> > > +    .size       = sizeof(struct Xen9pfsDev),  
> > 
> > ... s/struct //
> > 
> > > +    .flags      = DEVOPS_FLAG_NEED_GNTDEV,
> > > +    .alloc      = xen_9pfs_alloc,
> > > +    .init       = xen_9pfs_init,
> > > +    .initialise    = xen_9pfs_connect,
> > > +    .disconnect = xen_9pfs_disconnect,
> > > +    .free       = xen_9pfs_free,
> > > +};  
> > 
> > With the above comments addressed:
> > 
> > Reviewed-by: Greg Kurz <groug@kaod.org>

Thank you for the quick review and useful comments. I'll address them in
the next version of the series.


> Hmm... there's still a problem actually. This patch breaks build for some
> targets with '--enable-xen --enable-virtfs':
> 
>   LINK    cris-softmmu/qemu-system-cris
> ../hw/xen/xen_backend.o: In function `xen_be_register_common':
> /home/greg/Work/qemu/qemu-9p/hw/xen/xen_backend.c:588: undefined reference to `xen_9pfs_ops'

I could reproduce the problem


> This happens because only targets that support virtio and PCI pull the
> 9pfs/fsdev object files. This is an effort to have smaller QEMU binaries,
> based on the historical dependency of 9pfs on virtio. This patch breaks
> this assumption if CONFIG_XEN_BACKEND is defined but the target doesn't
> define CONFIG_VIRTIO and CONFIG_PCI.
> 
> Since 9pfs can now be used with another transport, I guess that the
> dependency on virtio and PCI isn't right anymore. The new condition
> for targets to support 9pfs should rather be something like:
> 
> CONFIG_VIRTFS == y && CONFIG_SOFTMMU == y && (CONFIG_VIRTIO == y || CONFIG_XEN_BACKEND == y)
> 
> This would cause all targets to pull the 9pfs/fsdev object files though.
> 
> So I have a question: do all targets need to support the Xen backend, really ?

Not really: Xen is only supported on x86 and ARM platforms today.
Typically, Xen is only enabled in QEMU for i386 or x86_64 softmmu
targets, even when used in an ARM context (long story short: the Xen PV
machine is arch-agnostic, but the QEMU build doesn't support that, so we
tied it to x86 just because we had to pick one).

In fact, I think the issue is that CONFIG_XEN_BACKEND is set wrongly by
the configure script. It's not an host property, but a target property
like CONFIG_XEN. We need:

diff --git a/configure b/configure
index 6c21975..6d8f752 100755
--- a/configure
+++ b/configure
@@ -5442,7 +5442,6 @@ if test "$virglrenderer" = "yes" ; then
   echo "VIRGL_LIBS=$virgl_libs" >> $config_host_mak
 fi
 if test "$xen" = "yes" ; then
-  echo "CONFIG_XEN_BACKEND=y" >> $config_host_mak
   echo "CONFIG_XEN_CTRL_INTERFACE_VERSION=$xen_ctrl_version" >> $config_host_mak
   if test "$xen_pv_domain_build" = "yes" ; then
     echo "CONFIG_XEN_PV_DOMAIN_BUILD=y" >> $config_host_mak
@@ -6028,6 +6027,7 @@ case "$target_name" in
   i386|x86_64)
     if test "$xen" = "yes" -a "$target_softmmu" = "yes" ; then
       echo "CONFIG_XEN=y" >> $config_target_mak
+      echo "CONFIG_XEN_BACKEND=y" >> $config_target_mak
       if test "$xen_pci_passthrough" = yes; then
         echo "CONFIG_XEN_PCI_PASSTHROUGH=y" >> "$config_target_mak"
       fi

With this change, and the other change you suggested:

  common-obj-$(CONFIG_XEN_BACKEND) += xen-9p-backend.o

I couldn't see any build issues.

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[PATCH 4/8] xen/9pfs: connect to the frontend

[Stefano Stabellini]

Write the limits of the backend to xenstore. Connect to the frontend.
Upon connection, allocate the rings according to the protocol
specification.

Initialize a QEMUBH to schedule work upon receiving an event channel
notification from the frontend.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: anthony.perard@citrix.com
CC: jgross@suse.com
CC: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
CC: Greg Kurz <groug@kaod.org>
---
 hw/9pfs/xen-9p-backend.c | 159 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 158 insertions(+), 1 deletion(-)

diff --git a/hw/9pfs/xen-9p-backend.c b/hw/9pfs/xen-9p-backend.c
index 924fb64..59e89fd 100644
--- a/hw/9pfs/xen-9p-backend.c
+++ b/hw/9pfs/xen-9p-backend.c
@@ -17,8 +17,35 @@
 #include "qemu/config-file.h"
 #include "fsdev/qemu-fsdev.h"
 
+#define VERSIONS "1"
+#define MAX_RINGS 8
+#define MAX_RING_ORDER 8
+
+struct Xen9pfsRing {
+    struct Xen9pfsDev *priv;
+
+    int ref;
+    xenevtchn_handle   *evtchndev;
+    int evtchn;
+    int local_port;
+    struct xen_9pfs_data_intf *intf;
+    unsigned char *data;
+    struct xen_9pfs_data ring;
+
+    QEMUBH *bh;
+
+    /* local copies, so that we can read/write PDU data directly from
+     * the ring */
+    RING_IDX out_cons, out_size, in_cons;
+    bool inprogress;
+};
+
 struct Xen9pfsDev {
     struct XenDevice xendev;  /* must be first */
+    V9fsState state;
+
+    int num_rings;
+    struct Xen9pfsRing *rings;
 };
 
 static ssize_t xen_9pfs_pdu_vmarshal(V9fsPDU *pdu,
@@ -67,22 +94,152 @@ static int xen_9pfs_init(struct XenDevice *xendev)
     return 0;
 }
 
+static void xen_9pfs_bh(void *opaque)
+{
+}
+
+static void xen_9pfs_evtchn_event(void *opaque)
+{
+}
+
 static int xen_9pfs_free(struct XenDevice *xendev)
 {
-    return -1;
+    int i;
+    struct Xen9pfsDev *xen_9pdev = container_of(xendev, struct Xen9pfsDev, xendev);
+
+    for (i = 0; i < xen_9pdev->num_rings; i++) {
+        if (xen_9pdev->rings[i].data != NULL) {
+            xengnttab_unmap(xen_9pdev->xendev.gnttabdev,
+                    xen_9pdev->rings[i].data,
+                    (1 << XEN_9PFS_RING_ORDER));
+        }
+        if (xen_9pdev->rings[i].intf != NULL) {
+            xengnttab_unmap(xen_9pdev->xendev.gnttabdev,
+                    xen_9pdev->rings[i].intf,
+                    1);
+        }
+        if (xen_9pdev->rings[i].evtchndev > 0) {
+            qemu_set_fd_handler(xenevtchn_fd(xen_9pdev->rings[i].evtchndev),
+                    NULL, NULL, NULL);
+            xenevtchn_unbind(xen_9pdev->rings[i].evtchndev, xen_9pdev->rings[i].local_port);
+        }
+        if (xen_9pdev->rings[i].bh != NULL) {
+            qemu_bh_delete(xen_9pdev->rings[i].bh);
+        }
+    }
+    g_free(xen_9pdev->rings);
+    return 0;
 }
 
 static int xen_9pfs_connect(struct XenDevice *xendev)
 {
+    int i;
+    struct Xen9pfsDev *xen_9pdev = container_of(xendev, struct Xen9pfsDev, xendev);
+    V9fsState *s = &xen_9pdev->state;
+    QemuOpts *fsdev;
+    char *security_model, *path;
+
+    if (xenstore_read_fe_int(&xen_9pdev->xendev, "num-rings",
+                             &xen_9pdev->num_rings) == -1 ||
+        xen_9pdev->num_rings > MAX_RINGS) {
+        return -1;
+    }
+
+    xen_9pdev->rings = g_malloc0(xen_9pdev->num_rings * sizeof(struct Xen9pfsRing));
+    for (i = 0; i < xen_9pdev->num_rings; i++) {
+        char str[16];
+
+        xen_9pdev->rings[i].priv = xen_9pdev;
+        xen_9pdev->rings[i].evtchn = -1;
+        xen_9pdev->rings[i].local_port = -1;
+
+        sprintf(str, "ring-ref%u", i);
+        if (xenstore_read_fe_int(&xen_9pdev->xendev, str,
+                                 &xen_9pdev->rings[i].ref) == -1) {
+            goto out;
+        }
+        sprintf(str, "event-channel-%u", i);
+        if (xenstore_read_fe_int(&xen_9pdev->xendev, str,
+                                 &xen_9pdev->rings[i].evtchn) == -1) {
+            goto out;
+        }
+
+        xen_9pdev->rings[i].intf =  xengnttab_map_grant_ref(
+                xen_9pdev->xendev.gnttabdev,
+                xen_9pdev->xendev.dom,
+                xen_9pdev->rings[i].ref,
+                PROT_READ | PROT_WRITE);
+        if (!xen_9pdev->rings[i].intf) {
+            goto out;
+        }
+        xen_9pdev->rings[i].data = xengnttab_map_domain_grant_refs(
+                xen_9pdev->xendev.gnttabdev,
+                (1 << XEN_9PFS_RING_ORDER),
+                xen_9pdev->xendev.dom,
+                xen_9pdev->rings[i].intf->ref,
+                PROT_READ | PROT_WRITE);
+        if (!xen_9pdev->rings[i].data) {
+            goto out;
+        }
+        xen_9pdev->rings[i].ring.in = xen_9pdev->rings[i].data;
+        xen_9pdev->rings[i].ring.out = xen_9pdev->rings[i].data + XEN_9PFS_RING_SIZE;
+
+        xen_9pdev->rings[i].bh = qemu_bh_new(xen_9pfs_bh, &xen_9pdev->rings[i]);
+        xen_9pdev->rings[i].out_cons = 0;
+        xen_9pdev->rings[i].out_size = 0;
+        xen_9pdev->rings[i].inprogress = false;
+
+
+        xen_9pdev->rings[i].evtchndev = xenevtchn_open(NULL, 0);
+        if (xen_9pdev->rings[i].evtchndev == NULL) {
+            goto out;
+        }
+        fcntl(xenevtchn_fd(xen_9pdev->rings[i].evtchndev), F_SETFD, FD_CLOEXEC);
+        xen_9pdev->rings[i].local_port = xenevtchn_bind_interdomain
+            (xen_9pdev->rings[i].evtchndev, xendev->dom, xen_9pdev->rings[i].evtchn);
+        if (xen_9pdev->rings[i].local_port == -1) {
+            xen_pv_printf(xendev, 0, "xenevtchn_bind_interdomain failed port=%d\n",
+                          xen_9pdev->rings[i].evtchn);
+            goto out;
+        }
+        xen_pv_printf(xendev, 2, "bind evtchn port %d\n", xendev->local_port);
+        qemu_set_fd_handler(xenevtchn_fd(xen_9pdev->rings[i].evtchndev),
+                xen_9pfs_evtchn_event, NULL, &xen_9pdev->rings[i]);
+    }
+
+    security_model = xenstore_read_be_str(xendev, "security_model");
+    path = xenstore_read_be_str(xendev, "path");
+    s->fsconf.fsdev_id = g_malloc(strlen("xen9p") + 6);
+    sprintf(s->fsconf.fsdev_id, "xen9p%d", xendev->dev);
+    s->fsconf.tag = xenstore_read_fe_str(xendev, "tag");
+    v9fs_register_transport(s, &xen_9p_transport);
+    fsdev = qemu_opts_create(qemu_find_opts("fsdev"),
+            s->fsconf.tag,
+            1, NULL);
+    qemu_opt_set(fsdev, "fsdriver", "local", NULL);
+    qemu_opt_set(fsdev, "path", path, NULL);
+    qemu_opt_set(fsdev, "security_model", security_model, NULL);
+    qemu_opts_set_id(fsdev, s->fsconf.fsdev_id);
+    qemu_fsdev_add(fsdev);
+    v9fs_device_realize_common(s, NULL);
+
     return 0;
+
+out:
+    xen_9pfs_free(xendev);
+    return -1;
 }
 
 static void xen_9pfs_alloc(struct XenDevice *xendev)
 {
+    xenstore_write_be_str(xendev, "versions", VERSIONS);
+    xenstore_write_be_int(xendev, "max-rings", MAX_RINGS);
+    xenstore_write_be_int(xendev, "max-ring-page-order", MAX_RING_ORDER);
 }
 
 static void xen_9pfs_disconnect(struct XenDevice *xendev)
 {
+    /* Dynamic hotplug of PV filesystems at runtime is not supported. */
 }
 
 struct XenDevOps xen_9pfs_ops = {
-- 
1.9.1


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[PATCH 5/8] xen/9pfs: receive requests from the frontend

[Stefano Stabellini]

Upon receiving an event channel notification from the frontend, schedule
the bottom half. From the bottom half, read one request from the ring,
create a pdu and call pdu_submit to handle it.

For now, only handle one request per ring at a time.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: anthony.perard@citrix.com
CC: jgross@suse.com
CC: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
CC: Greg Kurz <groug@kaod.org>
---
 hw/9pfs/xen-9p-backend.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/hw/9pfs/xen-9p-backend.c b/hw/9pfs/xen-9p-backend.c
index 59e89fd..d4c3d36 100644
--- a/hw/9pfs/xen-9p-backend.c
+++ b/hw/9pfs/xen-9p-backend.c
@@ -94,12 +94,59 @@ static int xen_9pfs_init(struct XenDevice *xendev)
     return 0;
 }
 
+static int xen_9pfs_receive(struct Xen9pfsRing *ring)
+{
+    struct xen_9pfs_header h;
+    RING_IDX cons, prod, masked_prod, masked_cons;
+    V9fsPDU *pdu;
+
+    if (ring->inprogress) {
+        return 0;
+    }
+
+    cons = ring->intf->out_cons;
+    prod = ring->intf->out_prod;
+    xen_rmb();
+
+    if (xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE) < sizeof(h)) {
+        return 0;
+    }
+    ring->inprogress = true;
+
+    masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE);
+    masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
+
+    xen_9pfs_read_packet(ring->ring.out, masked_prod, &masked_cons,
+                         XEN_9PFS_RING_SIZE, (uint8_t*) &h, sizeof(h));
+
+    pdu = pdu_alloc(&ring->priv->state);
+    pdu->size = h.size;
+    pdu->id = h.id;
+    pdu->tag = h.tag;
+    ring->out_size = h.size;
+    ring->out_cons = cons + h.size;
+
+    qemu_co_queue_init(&pdu->complete);
+    pdu_submit(pdu);
+
+    return 0;
+}
+
 static void xen_9pfs_bh(void *opaque)
 {
+    struct Xen9pfsRing *ring = opaque;
+    xen_9pfs_receive(ring);
 }
 
 static void xen_9pfs_evtchn_event(void *opaque)
 {
+    struct Xen9pfsRing *ring = opaque;
+    evtchn_port_t port;
+
+    port = xenevtchn_pending(ring->evtchndev);
+    xenevtchn_unmask(ring->evtchndev, port);
+
+    qemu_bh_schedule(ring->bh);
 }
 
 static int xen_9pfs_free(struct XenDevice *xendev)
-- 
1.9.1


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[PATCH 6/8] xen/9pfs: implement in/out_iov_from_pdu and vmarshal/vunmarshal

[Stefano Stabellini]

Implement xen_9pfs_init_in/out_iov_from_pdu and
xen_9pfs_pdu_vmarshal/vunmarshall by creating new sg pointing to the
data on the ring.

This is safe as we only handle one request per ring at any given time.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: anthony.perard@citrix.com
CC: jgross@suse.com
CC: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
CC: Greg Kurz <groug@kaod.org>
---
 hw/9pfs/xen-9p-backend.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 89 insertions(+), 2 deletions(-)

diff --git a/hw/9pfs/xen-9p-backend.c b/hw/9pfs/xen-9p-backend.c
index d4c3d36..0570e07 100644
--- a/hw/9pfs/xen-9p-backend.c
+++ b/hw/9pfs/xen-9p-backend.c
@@ -48,12 +48,77 @@ struct Xen9pfsDev {
     struct Xen9pfsRing *rings;
 };
 
+static void xen_9pfs_in_sg(struct Xen9pfsRing *ring,
+                           struct iovec *in_sg,
+                           int *num,
+                           uint32_t idx,
+                           uint32_t size)
+{
+    RING_IDX cons, prod, masked_prod, masked_cons;
+
+    cons = ring->intf->in_cons;
+    prod = ring->intf->in_prod;
+    xen_rmb();
+    masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE);
+    masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
+
+    if (masked_prod < masked_cons) {
+        in_sg[0].iov_base = ring->ring.in + masked_prod;
+        in_sg[0].iov_len = masked_cons - masked_prod;
+        *num = 1;
+    } else {
+        in_sg[0].iov_base = ring->ring.in + masked_prod;
+        in_sg[0].iov_len = XEN_9PFS_RING_SIZE - masked_prod;
+        in_sg[1].iov_base = ring->ring.in;
+        in_sg[1].iov_len = masked_cons;
+        *num = 2;
+    }
+}
+
+static void xen_9pfs_out_sg(struct Xen9pfsRing *ring,
+                            struct iovec *out_sg,
+                            int *num,
+                            uint32_t idx)
+{
+    RING_IDX cons, prod, masked_prod, masked_cons;
+
+    cons = ring->intf->out_cons;
+    prod = ring->intf->out_prod;
+    xen_rmb();
+    masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE);
+    masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
+
+    if (masked_cons < masked_prod) {
+        out_sg[0].iov_base = ring->ring.out + masked_cons;
+        out_sg[0].iov_len = ring->out_size;
+        *num = 1;
+    } else {
+        if (ring->out_size > (XEN_9PFS_RING_SIZE - masked_cons)) {
+            out_sg[0].iov_base = ring->ring.out + masked_cons;
+            out_sg[0].iov_len = XEN_9PFS_RING_SIZE - masked_cons;
+            out_sg[1].iov_base = ring->ring.out;
+            out_sg[1].iov_len = ring->out_size - (XEN_9PFS_RING_SIZE - masked_cons);
+            *num = 2;
+        } else {
+            out_sg[0].iov_base = ring->ring.out + masked_cons;
+            out_sg[0].iov_len = ring->out_size;
+            *num = 1;
+        }
+    }
+}
+
 static ssize_t xen_9pfs_pdu_vmarshal(V9fsPDU *pdu,
                                      size_t offset,
                                      const char *fmt,
                                      va_list ap)
 {
-    return 0;
+    struct Xen9pfsDev *xen_9pfs = container_of(pdu->s, struct Xen9pfsDev, state);
+    struct iovec in_sg[2];
+    int num;
+
+    xen_9pfs_in_sg(&xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings],
+                   in_sg, &num, pdu->idx, ROUND_UP(offset + 128, 512));
+    return v9fs_iov_vmarshal(in_sg, num, offset, 0, fmt, ap);
 }
 
 static ssize_t xen_9pfs_pdu_vunmarshal(V9fsPDU *pdu,
@@ -61,13 +126,27 @@ static ssize_t xen_9pfs_pdu_vunmarshal(V9fsPDU *pdu,
                                        const char *fmt,
                                        va_list ap)
 {
-    return 0;
+    struct Xen9pfsDev *xen_9pfs = container_of(pdu->s, struct Xen9pfsDev, state);
+    struct iovec out_sg[2];
+    int num;
+
+    xen_9pfs_out_sg(&xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings],
+                    out_sg, &num, pdu->idx);
+    return v9fs_iov_vunmarshal(out_sg, num, offset, 0, fmt, ap);
 }
 
 static void xen_9pfs_init_out_iov_from_pdu(V9fsPDU *pdu,
                                            struct iovec **piov,
                                            unsigned int *pniov)
 {
+    struct Xen9pfsDev *xen_9pfs = container_of(pdu->s, struct Xen9pfsDev, state);
+    struct Xen9pfsRing *ring = &xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings];
+    struct iovec *sg = g_malloc0(sizeof(*sg)*2);
+    int num;
+
+    xen_9pfs_out_sg(ring, sg, &num, pdu->idx);
+    *piov = sg;
+    *pniov = num;
 }
 
 static void xen_9pfs_init_in_iov_from_pdu(V9fsPDU *pdu,
@@ -75,6 +154,14 @@ static void xen_9pfs_init_in_iov_from_pdu(V9fsPDU *pdu,
                                           unsigned int *pniov,
                                           size_t size)
 {
+    struct Xen9pfsDev *xen_9pfs = container_of(pdu->s, struct Xen9pfsDev, state);
+    struct Xen9pfsRing *ring = &xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings];
+    struct iovec *sg = g_malloc0(sizeof(*sg)*2);
+    int num;
+
+    xen_9pfs_in_sg(ring, sg, &num, pdu->idx, size);
+    *piov = sg;
+    *pniov = num;
 }
 
 static void xen_9pfs_push_and_notify(V9fsPDU *pdu)
-- 
1.9.1


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[PATCH 7/8] xen/9pfs: send responses back to the frontend

[Stefano Stabellini]

Once a request is completed, xen_9pfs_push_and_notify gets called. In
xen_9pfs_push_and_notify, update the indexes (data has already been
copied to the sg by the common code) and send a notification to the
frontend.

Schedule the bottom-half to check if we already have any other requests
pending.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: anthony.perard@citrix.com
CC: jgross@suse.com
CC: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
CC: Greg Kurz <groug@kaod.org>
---
 hw/9pfs/xen-9p-backend.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/hw/9pfs/xen-9p-backend.c b/hw/9pfs/xen-9p-backend.c
index 0570e07..80a8810 100644
--- a/hw/9pfs/xen-9p-backend.c
+++ b/hw/9pfs/xen-9p-backend.c
@@ -166,6 +166,22 @@ static void xen_9pfs_init_in_iov_from_pdu(V9fsPDU *pdu,
 
 static void xen_9pfs_push_and_notify(V9fsPDU *pdu)
 {
+    RING_IDX prod;
+    struct Xen9pfsDev *priv = container_of(pdu->s, struct Xen9pfsDev, state);
+    struct Xen9pfsRing *ring = &priv->rings[pdu->tag % priv->num_rings];
+
+    ring->intf->out_cons = ring->out_cons;
+    xen_wmb();
+
+    prod = ring->intf->in_prod;
+    xen_rmb();
+    ring->intf->in_prod = prod + pdu->size;
+    xen_wmb();
+
+    ring->inprogress = false;
+    xenevtchn_notify(ring->evtchndev, ring->local_port);
+
+    qemu_bh_schedule(ring->bh);
 }
 
 static const struct V9fsTransport xen_9p_transport = {
-- 
1.9.1


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[PATCH 8/8] xen/9pfs: build and register Xen 9pfs backend

[Stefano Stabellini]

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: anthony.perard@citrix.com
CC: jgross@suse.com
CC: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
CC: Greg Kurz <groug@kaod.org>
---
 hw/9pfs/Makefile.objs        | 1 +
 hw/xen/xen_backend.c         | 1 +
 include/hw/xen/xen_backend.h | 1 +
 3 files changed, 3 insertions(+)

diff --git a/hw/9pfs/Makefile.objs b/hw/9pfs/Makefile.objs
index da0ae0c..76a81c3 100644
--- a/hw/9pfs/Makefile.objs
+++ b/hw/9pfs/Makefile.objs
@@ -7,3 +7,4 @@ common-obj-$(CONFIG_OPEN_BY_HANDLE) +=  9p-handle.o
 common-obj-y += 9p-proxy.o
 
 obj-y += virtio-9p-device.o
+obj-y += xen-9p-backend.o
diff --git a/hw/xen/xen_backend.c b/hw/xen/xen_backend.c
index 6c21c37..7aa347d 100644
--- a/hw/xen/xen_backend.c
+++ b/hw/xen/xen_backend.c
@@ -585,6 +585,7 @@ void xen_be_register_common(void)
     xen_be_register("console", &xen_console_ops);
     xen_be_register("vkbd", &xen_kbdmouse_ops);
     xen_be_register("qdisk", &xen_blkdev_ops);
+    xen_be_register("9pfs", &xen_9pfs_ops);
 #ifdef CONFIG_USB_LIBUSB
     xen_be_register("qusb", &xen_usb_ops);
 #endif
diff --git a/include/hw/xen/xen_backend.h b/include/hw/xen/xen_backend.h
index 4f4799a..84e686c 100644
--- a/include/hw/xen/xen_backend.h
+++ b/include/hw/xen/xen_backend.h
@@ -49,6 +49,7 @@ extern struct XenDevOps xen_console_ops;      /* xen_console.c     */
 extern struct XenDevOps xen_kbdmouse_ops;     /* xen_framebuffer.c */
 extern struct XenDevOps xen_framebuffer_ops;  /* xen_framebuffer.c */
 extern struct XenDevOps xen_blkdev_ops;       /* xen_disk.c        */
+extern struct XenDevOps xen_9pfs_ops;       /* xen-9p-backend.c        */
 extern struct XenDevOps xen_netdev_ops;       /* xen_nic.c         */
 #ifdef CONFIG_USB_LIBUSB
 extern struct XenDevOps xen_usb_ops;          /* xen-usb.c         */
-- 
1.9.1


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Re: [Qemu-devel] [PATCH 8/8] xen/9pfs: build and register Xen 9pfs backend

[Greg Kurz]

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On Mon,  6 Mar 2017 18:12:48 -0800
Stefano Stabellini <sstabellini@kernel.org> wrote:

> Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
> CC: anthony.perard@citrix.com
> CC: jgross@suse.com
> CC: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> CC: Greg Kurz <groug@kaod.org>
> ---
>  hw/9pfs/Makefile.objs        | 1 +
>  hw/xen/xen_backend.c         | 1 +
>  include/hw/xen/xen_backend.h | 1 +
>  3 files changed, 3 insertions(+)
> 
> diff --git a/hw/9pfs/Makefile.objs b/hw/9pfs/Makefile.objs
> index da0ae0c..76a81c3 100644
> --- a/hw/9pfs/Makefile.objs
> +++ b/hw/9pfs/Makefile.objs
> @@ -7,3 +7,4 @@ common-obj-$(CONFIG_OPEN_BY_HANDLE) +=  9p-handle.o
>  common-obj-y += 9p-proxy.o
>  
>  obj-y += virtio-9p-device.o
> +obj-y += xen-9p-backend.o

The xen-9p-backend.c file seems to be target agnostic: it can be built
only once. Also, it should only be built if QEMU was configured with
Xen support. Hence:

obj-common-$(CONFIG_XEN_BACKEND) += xen-9p-backend.o

> diff --git a/hw/xen/xen_backend.c b/hw/xen/xen_backend.c
> index 6c21c37..7aa347d 100644
> --- a/hw/xen/xen_backend.c
> +++ b/hw/xen/xen_backend.c
> @@ -585,6 +585,7 @@ void xen_be_register_common(void)
>      xen_be_register("console", &xen_console_ops);
>      xen_be_register("vkbd", &xen_kbdmouse_ops);
>      xen_be_register("qdisk", &xen_blkdev_ops);

#ifdef CONFIG_VIRTFS

> +    xen_be_register("9pfs", &xen_9pfs_ops);

#endif

>  #ifdef CONFIG_USB_LIBUSB
>      xen_be_register("qusb", &xen_usb_ops);
>  #endif
> diff --git a/include/hw/xen/xen_backend.h b/include/hw/xen/xen_backend.h
> index 4f4799a..84e686c 100644
> --- a/include/hw/xen/xen_backend.h
> +++ b/include/hw/xen/xen_backend.h
> @@ -49,6 +49,7 @@ extern struct XenDevOps xen_console_ops;      /* xen_console.c     */
>  extern struct XenDevOps xen_kbdmouse_ops;     /* xen_framebuffer.c */
>  extern struct XenDevOps xen_framebuffer_ops;  /* xen_framebuffer.c */
>  extern struct XenDevOps xen_blkdev_ops;       /* xen_disk.c        */
> +extern struct XenDevOps xen_9pfs_ops;       /* xen-9p-backend.c        */

ditto

>  extern struct XenDevOps xen_netdev_ops;       /* xen_nic.c         */
>  #ifdef CONFIG_USB_LIBUSB
>  extern struct XenDevOps xen_usb_ops;          /* xen-usb.c         */

With the above fixes.

Reviewed-by: Greg Kurz <groug@kaod.org>

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