Commit 1063b8b1 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Anthony Liguori
Browse files

virtio-blk: add SGI_IO passthru support 



[had the qemu list address wrong the first time, reply to this message,
 not the previous if you were on Cc]

Add support for SG_IO passthru (packet commands) to the virtio-blk
backend.  Conceptually based on an older patch from Hannes Reinecke
but largely rewritten to match the code structure and layering in
virtio-blk.

Note that currently we issue the hose SG_IO synchronously.  We could
easily switch to async I/O, but that would required either bloating
the VirtIOBlockReq by the size of struct sg_io_hdr or an additional
memory allocation for each SG_IO request.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarAnthony Liguori <aliguori@us.ibm.com>
parent 451c4abd

hw/virtio-blk.c

+116 −7
Original line number Diff line number Diff line
@@ -15,6 +15,9 @@ 
#include <sysemu.h>

#include "virtio-blk.h"

#include "block_int.h"

#ifdef __linux__

# include <scsi/sg.h>

#endif



typedef struct VirtIOBlock

{
@@ -35,6 +38,7 @@ typedef struct VirtIOBlockReq 
    VirtQueueElement elem;

    struct virtio_blk_inhdr *in;

    struct virtio_blk_outhdr *out;

    struct virtio_scsi_inhdr *scsi;

    QEMUIOVector qiov;

    struct VirtIOBlockReq *next;

} VirtIOBlockReq;
@@ -103,6 +107,108 @@ static VirtIOBlockReq *virtio_blk_get_request(VirtIOBlock *s) 
    return req;

}



#ifdef __linux__

static void virtio_blk_handle_scsi(VirtIOBlockReq *req)

{

    struct sg_io_hdr hdr;

    int ret, size = 0;

    int status;

    int i;



    /*

     * We require at least one output segment each for the virtio_blk_outhdr

     * and the SCSI command block.

     *

     * We also at least require the virtio_blk_inhdr, the virtio_scsi_inhdr

     * and the sense buffer pointer in the input segments.

     */

    if (req->elem.out_num < 2 || req->elem.in_num < 3) {

        virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);

        return;

    }



    /*

     * No support for bidirection commands yet.

     */

    if (req->elem.out_num > 2 && req->elem.in_num > 3) {

        virtio_blk_req_complete(req, VIRTIO_BLK_S_UNSUPP);

        return;

    }



    /*

     * The scsi inhdr is placed in the second-to-last input segment, just

     * before the regular inhdr.

     */

    req->scsi = (void *)req->elem.in_sg[req->elem.in_num - 2].iov_base;

    size = sizeof(*req->in) + sizeof(*req->scsi);



    memset(&hdr, 0, sizeof(struct sg_io_hdr));

    hdr.interface_id = 'S';

    hdr.cmd_len = req->elem.out_sg[1].iov_len;

    hdr.cmdp = req->elem.out_sg[1].iov_base;

    hdr.dxfer_len = 0;



    if (req->elem.out_num > 2) {

        /*

         * If there are more than the minimally required 2 output segments

         * there is write payload starting from the third iovec.

         */

        hdr.dxfer_direction = SG_DXFER_TO_DEV;

        hdr.iovec_count = req->elem.out_num - 2;



        for (i = 0; i < hdr.iovec_count; i++)

            hdr.dxfer_len += req->elem.out_sg[i + 2].iov_len;



        hdr.dxferp = req->elem.out_sg + 2;



    } else if (req->elem.in_num > 3) {

        /*

         * If we have more than 3 input segments the guest wants to actually

         * read data.

         */

        hdr.dxfer_direction = SG_DXFER_FROM_DEV;

        hdr.iovec_count = req->elem.in_num - 3;

        for (i = 0; i < hdr.iovec_count; i++)

            hdr.dxfer_len += req->elem.in_sg[i].iov_len;



        hdr.dxferp = req->elem.in_sg;

        size += hdr.dxfer_len;

    } else {

        /*

         * Some SCSI commands don't actually transfer any data.

         */

        hdr.dxfer_direction = SG_DXFER_NONE;

    }



    hdr.sbp = req->elem.in_sg[req->elem.in_num - 3].iov_base;

    hdr.mx_sb_len = req->elem.in_sg[req->elem.in_num - 3].iov_len;

    size += hdr.mx_sb_len;



    ret = bdrv_ioctl(req->dev->bs, SG_IO, &hdr);

    if (ret) {

        status = VIRTIO_BLK_S_UNSUPP;

        hdr.status = ret;

        hdr.resid = hdr.dxfer_len;

    } else if (hdr.status) {

        status = VIRTIO_BLK_S_IOERR;

    } else {

        status = VIRTIO_BLK_S_OK;

    }



    req->scsi->errors = hdr.status;

    req->scsi->residual = hdr.resid;

    req->scsi->sense_len = hdr.sb_len_wr;

    req->scsi->data_len = hdr.dxfer_len;



    virtio_blk_req_complete(req, status);

}

#else

static void virtio_blk_handle_scsi(VirtIOBlockReq *req)

{

    virtio_blk_req_complete(req, VIRTIO_BLK_S_UNSUPP);

}

#endif /* __linux__ */



static void virtio_blk_handle_write(VirtIOBlockReq *req)

{

    bdrv_aio_writev(req->dev->bs, req->out->sector, &req->qiov,
@@ -136,12 +242,7 @@ static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq) 
        req->in = (void *)req->elem.in_sg[req->elem.in_num - 1].iov_base;



        if (req->out->type & VIRTIO_BLK_T_SCSI_CMD) {

            unsigned int len = sizeof(*req->in);



            req->in->status = VIRTIO_BLK_S_UNSUPP;

            virtqueue_push(vq, &req->elem, len);

            virtio_notify(vdev, vq);

            qemu_free(req);

            virtio_blk_handle_scsi(req);

        } else if (req->out->type & VIRTIO_BLK_T_OUT) {

            qemu_iovec_init_external(&req->qiov, &req->elem.out_sg[1],

                                     req->elem.out_num - 1);
@@ -203,7 +304,15 @@ static void virtio_blk_update_config(VirtIODevice *vdev, uint8_t *config) 


static uint32_t virtio_blk_get_features(VirtIODevice *vdev)

{

    return (1 << VIRTIO_BLK_F_SEG_MAX | 1 << VIRTIO_BLK_F_GEOMETRY);

    uint32_t features = 0;



    features |= (1 << VIRTIO_BLK_F_SEG_MAX);

    features |= (1 << VIRTIO_BLK_F_GEOMETRY);

#ifdef __linux__

    features |= (1 << VIRTIO_BLK_F_SCSI);

#endif



    return features;

}



static void virtio_blk_save(QEMUFile *f, void *opaque)

hw/virtio-blk.h

+12 −0
Original line number Diff line number Diff line
@@ -28,6 +28,9 @@ 
#define VIRTIO_BLK_F_SIZE_MAX   1       /* Indicates maximum segment size */

#define VIRTIO_BLK_F_SEG_MAX    2       /* Indicates maximum # of segments */

#define VIRTIO_BLK_F_GEOMETRY   4       /* Indicates support of legacy geometry */

#define VIRTIO_BLK_F_RO         5       /* Disk is read-only */

#define VIRTIO_BLK_F_BLK_SIZE   6       /* Block size of disk is available*/

#define VIRTIO_BLK_F_SCSI       7       /* Supports scsi command passthru */



struct virtio_blk_config

{
@@ -70,6 +73,15 @@ struct virtio_blk_inhdr 
    unsigned char status;

};



/* SCSI pass-through header */

struct virtio_scsi_inhdr

{

    uint32_t errors;

    uint32_t data_len;

    uint32_t sense_len;

    uint32_t residual;

};



void *virtio_blk_init(PCIBus *bus, BlockDriverState *bs);



#endif