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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v2 2/9] xen: import ring.h from xen
On Mon, 13 Mar 2017 16:55:53 -0700
Stefano Stabellini <sstabellini@xxxxxxxxxx> wrote:
> 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.
>
What kind of problems ?
> Signed-off-by: Stefano Stabellini <stefano@xxxxxxxxxxx>
> CC: anthony.perard@xxxxxxxxxx
> CC: jgross@xxxxxxxx
> ---
> NB: The new macros have not been committed to Xen yet. Do not apply this
> patch until they do.
Why ? Does this break compat with older Xen ?
> ---
> ---
> 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:
> + */
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