Re: [Qemu-devel] [PATCH 5/7] xen: add block device backend driver.

[Anthony Liguori <anthony@codemonkey.ws>]

Gerd Hoffmann wrote:
> This patch adds a block device backend driver to qemu.  It is a pure
> userspace implemention using the gntdev interface.  It uses "qdisk" as
> backend name in xenstore so it doesn't interfere with the other existing
> backends (blkback aka "vbd" and tapdisk aka "tap").
>
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  Makefile.target  |    2 +-
>  hw/xen-backend.h |    2 +
>  hw/xen-blkif.h   |  103 ++++++++
>  hw/xen-disk.c    |  681 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  hw/xen-machine.c |    1 +
>  sysemu.h         |    2 +-
>  vl.c             |    4 +
>  7 files changed, 793 insertions(+), 2 deletions(-)
>  create mode 100644 hw/xen-blkif.h
>  create mode 100644 hw/xen-disk.c
>
> diff --git a/Makefile.target b/Makefile.target
> index 66d41ee..2d599d2 100644
> --- a/Makefile.target
> +++ b/Makefile.target
> @@ -517,7 +517,7 @@ endif
>  
>  # xen backend driver support
>  XEN_OBJS := xen-machine.o xen-backend.o
> -XEN_OBJS += xen-console.o xen-framebuffer.o
> +XEN_OBJS += xen-console.o xen-framebuffer.o xen-disk.o
>  ifeq ($(CONFIG_XEN), yes)
>    OBJS += $(XEN_OBJS)
>    LIBS += $(XEN_LIBS)
> diff --git a/hw/xen-backend.h b/hw/xen-backend.h
> index 3facf90..941b0a6 100644
> --- a/hw/xen-backend.h
> +++ b/hw/xen-backend.h
> @@ -10,6 +10,7 @@
>  
>  #include "hw.h"
>  #include "xen.h"
> +#include "sysemu.h"
>  
>  /*
>   * tweaks needed to build with different xen versions
> @@ -118,6 +119,7 @@ void xen_be_printf(struct xendev *xendev, int msg_level, const char *fmt, ...)
>  struct devops xen_console_ops;      /* xen_console.c     */
>  struct devops xen_kbdmouse_ops;     /* xen_framebuffer.c */
>  struct devops xen_framebuffer_ops;  /* xen_framebuffer.c */
> +struct devops xen_blkdev_ops;       /* xen_disk.c        */
>  
>  void xen_set_display(int domid, DisplayState *ds);
>  
> diff --git a/hw/xen-blkif.h b/hw/xen-blkif.h
> new file mode 100644
> index 0000000..254a5fd
> --- /dev/null
> +++ b/hw/xen-blkif.h
> @@ -0,0 +1,103 @@
> +#ifndef __XEN_BLKIF_H__
> +#define __XEN_BLKIF_H__
> +
> +#include <xen/io/ring.h>
> +#include <xen/io/blkif.h>
> +#include <xen/io/protocols.h>
> +
> +/* Not a real protocol.  Used to generate ring structs which contain
> + * the elements common to all protocols only.  This way we get a
> + * compiler-checkable way to use common struct elements, so we can
> + * avoid using switch(protocol) in a number of places.  */
> +struct blkif_common_request {
> +	char dummy;
> +};
> +struct blkif_common_response {
> +	char dummy;
> +};
> +
> +/* i386 protocol version */
> +#pragma pack(push, 4)
> +struct blkif_x86_32_request {
> +	uint8_t        operation;    /* BLKIF_OP_???                         */
> +	uint8_t        nr_segments;  /* number of segments                   */
> +	blkif_vdev_t   handle;       /* only for read/write requests         */
> +	uint64_t       id;           /* private guest value, echoed in resp  */
> +	blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
> +	struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
> +};
> +struct blkif_x86_32_response {
> +	uint64_t        id;              /* copied from request */
> +	uint8_t         operation;       /* copied from request */
> +	int16_t         status;          /* BLKIF_RSP_???       */
> +};
> +typedef struct blkif_x86_32_request blkif_x86_32_request_t;
> +typedef struct blkif_x86_32_response blkif_x86_32_response_t;
> +#pragma pack(pop)
> +
> +/* x86_64 protocol version */
> +struct blkif_x86_64_request {
> +	uint8_t        operation;    /* BLKIF_OP_???                         */
> +	uint8_t        nr_segments;  /* number of segments                   */
> +	blkif_vdev_t   handle;       /* only for read/write requests         */
> +	uint64_t       __attribute__((__aligned__(8))) id;
> +	blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
> +	struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
> +};
> +struct blkif_x86_64_response {
> +	uint64_t       __attribute__((__aligned__(8))) id;
> +	uint8_t         operation;       /* copied from request */
> +	int16_t         status;          /* BLKIF_RSP_???       */
> +};
> +typedef struct blkif_x86_64_request blkif_x86_64_request_t;
> +typedef struct blkif_x86_64_response blkif_x86_64_response_t;
> +
> +DEFINE_RING_TYPES(blkif_common, struct blkif_common_request, struct blkif_common_response);
> +DEFINE_RING_TYPES(blkif_x86_32, struct blkif_x86_32_request, struct blkif_x86_32_response);
> +DEFINE_RING_TYPES(blkif_x86_64, struct blkif_x86_64_request, struct blkif_x86_64_response);
> +
> +union blkif_back_rings {
> +	blkif_back_ring_t        native;
> +	blkif_common_back_ring_t common;
> +	blkif_x86_32_back_ring_t x86_32;
> +	blkif_x86_64_back_ring_t x86_64;
> +};
> +typedef union blkif_back_rings blkif_back_rings_t;
> +
> +enum blkif_protocol {
> +	BLKIF_PROTOCOL_NATIVE = 1,
> +	BLKIF_PROTOCOL_X86_32 = 2,
> +	BLKIF_PROTOCOL_X86_64 = 3,
> +};
> +
> +static void inline blkif_get_x86_32_req(blkif_request_t *dst, blkif_x86_32_request_t *src)
> +{
> +	int i, n = BLKIF_MAX_SEGMENTS_PER_REQUEST;
> +
> +	dst->operation = src->operation;
> +	dst->nr_segments = src->nr_segments;
> +	dst->handle = src->handle;
> +	dst->id = src->id;
> +	dst->sector_number = src->sector_number;
> +	if (n > src->nr_segments)
> +		n = src->nr_segments;
> +	for (i = 0; i < n; i++)
> +		dst->seg[i] = src->seg[i];
> +}
> +
> +static void inline blkif_get_x86_64_req(blkif_request_t *dst, blkif_x86_64_request_t *src)
> +{
> +	int i, n = BLKIF_MAX_SEGMENTS_PER_REQUEST;
> +
> +	dst->operation = src->operation;
> +	dst->nr_segments = src->nr_segments;
> +	dst->handle = src->handle;
> +	dst->id = src->id;
> +	dst->sector_number = src->sector_number;
> +	if (n > src->nr_segments)
> +		n = src->nr_segments;
> +	for (i = 0; i < n; i++)
> +		dst->seg[i] = src->seg[i];
> +}
> +
> +#endif /* __XEN_BLKIF_H__ */
> diff --git a/hw/xen-disk.c b/hw/xen-disk.c
> new file mode 100644
> index 0000000..6947363
> --- /dev/null
> +++ b/hw/xen-disk.c
> @@ -0,0 +1,681 @@
> +/*
> + *  xen paravirt block device backend
> + *
> + *  FIXME: the code is designed to handle multiple outstanding
> + *  requests (using aio or using threads), which isn't used right
> + *  now due to limitations of the qemu block driver interface.
> + *
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License as published by
> + *  the Free Software Foundation; under version 2 of the License.
> + *
> + *  This program is distributed in the hope that it will be useful,
> + *  but WITHOUT ANY WARRANTY; without even the implied warranty of
> + *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + *  GNU General Public License for more details.
> + *
> + *  You should have received a copy of the GNU General Public License
> + *  along with this program; if not, write to the Free Software
> + *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
> + */
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <stdarg.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include <signal.h>
> +#include <inttypes.h>
> +#include <time.h>
> +#include <fcntl.h>
> +#include <errno.h>
> +#include <pthread.h>
>   

This doesn't seem to be needed?

Regards,

Anthony Liguori