Commit 3284fad7 authored by Paul Durrant's avatar Paul Durrant Committed by Stefano Stabellini
Browse files

xen-disk: add support for multi-page shared rings 



The blkif protocol has had provision for negotiation of multi-page shared
rings for some time now and many guest OS have support in their frontend
drivers.

This patch makes the necessary modifications to xen-disk support a shared
ring up to order 4 (i.e. 16 pages).

Signed-off-by: default avatarPaul Durrant <paul.durrant@citrix.com>
Signed-off-by: default avatarStefano Stabellini <sstabellini@kernel.org>
Reviewed-by: default avatarStefano Stabellini <sstabellini@kernel.org>
parent 976eba1c

hw/block/xen_disk.c

+113 −31
Original line number Diff line number Diff line
@@ -36,8 +36,6 @@ 


static int batch_maps   = 0;



static int max_requests = 32;



/* ------------------------------------------------------------- */



#define BLOCK_SIZE  512
@@ -84,6 +82,8 @@ struct ioreq { 
    BlockAcctCookie     acct;

};



#define MAX_RING_PAGE_ORDER 4



struct XenBlkDev {

    struct XenDevice    xendev;  /* must be first */

    char                *params;
@@ -94,7 +94,8 @@ struct XenBlkDev { 
    bool                directiosafe;

    const char          *fileproto;

    const char          *filename;

    int                 ring_ref;

    unsigned int        ring_ref[1 << MAX_RING_PAGE_ORDER];

    unsigned int        nr_ring_ref;

    void                *sring;

    int64_t             file_blk;

    int64_t             file_size;
@@ -110,6 +111,7 @@ struct XenBlkDev { 
    int                 requests_total;

    int                 requests_inflight;

    int                 requests_finished;

    unsigned int        max_requests;



    /* Persistent grants extension */

    gboolean            feature_discard;
@@ -199,7 +201,7 @@ static struct ioreq *ioreq_start(struct XenBlkDev *blkdev) 
    struct ioreq *ioreq = NULL;



    if (QLIST_EMPTY(&blkdev->freelist)) {

        if (blkdev->requests_total >= max_requests) {

        if (blkdev->requests_total >= blkdev->max_requests) {

            goto out;

        }

        /* allocate new struct */
@@ -904,7 +906,7 @@ static void blk_handle_requests(struct XenBlkDev *blkdev) 
        ioreq_runio_qemu_aio(ioreq);

    }



    if (blkdev->more_work && blkdev->requests_inflight < max_requests) {

    if (blkdev->more_work && blkdev->requests_inflight < blkdev->max_requests) {

        qemu_bh_schedule(blkdev->bh);

    }

}
@@ -917,15 +919,6 @@ static void blk_bh(void *opaque) 
    blk_handle_requests(blkdev);

}



/*

 * We need to account for the grant allocations requiring contiguous

 * chunks; the worst case number would be

 *     max_req * max_seg + (max_req - 1) * (max_seg - 1) + 1,

 * but in order to keep things simple just use

 *     2 * max_req * max_seg.

 */

#define MAX_GRANTS(max_req, max_seg) (2 * (max_req) * (max_seg))



static void blk_alloc(struct XenDevice *xendev)

{

    struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);
@@ -937,11 +930,6 @@ static void blk_alloc(struct XenDevice *xendev) 
    if (xen_mode != XEN_EMULATE) {

        batch_maps = 1;

    }

    if (xengnttab_set_max_grants(xendev->gnttabdev,

            MAX_GRANTS(max_requests, BLKIF_MAX_SEGMENTS_PER_REQUEST)) < 0) {

        xen_pv_printf(xendev, 0, "xengnttab_set_max_grants failed: %s\n",

                      strerror(errno));

    }

}



static void blk_parse_discard(struct XenBlkDev *blkdev)
@@ -1036,6 +1024,9 @@ static int blk_init(struct XenDevice *xendev) 
                          !blkdev->feature_grant_copy);

    xenstore_write_be_int(&blkdev->xendev, "info", info);



    xenstore_write_be_int(&blkdev->xendev, "max-ring-page-order",

                          MAX_RING_PAGE_ORDER);



    blk_parse_discard(blkdev);



    g_free(directiosafe);
@@ -1057,12 +1048,25 @@ out_error: 
    return -1;

}



/*

 * We need to account for the grant allocations requiring contiguous

 * chunks; the worst case number would be

 *     max_req * max_seg + (max_req - 1) * (max_seg - 1) + 1,

 * but in order to keep things simple just use

 *     2 * max_req * max_seg.

 */

#define MAX_GRANTS(max_req, max_seg) (2 * (max_req) * (max_seg))



static int blk_connect(struct XenDevice *xendev)

{

    struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);

    int pers, index, qflags;

    bool readonly = true;

    bool writethrough = true;

    int order, ring_ref;

    unsigned int ring_size, max_grants;

    unsigned int i;

    uint32_t *domids;



    /* read-only ? */

    if (blkdev->directiosafe) {
@@ -1137,9 +1141,42 @@ static int blk_connect(struct XenDevice *xendev) 
    xenstore_write_be_int64(&blkdev->xendev, "sectors",

                            blkdev->file_size / blkdev->file_blk);



    if (xenstore_read_fe_int(&blkdev->xendev, "ring-ref", &blkdev->ring_ref) == -1) {

    if (xenstore_read_fe_int(&blkdev->xendev, "ring-page-order",

                             &order) == -1) {

        blkdev->nr_ring_ref = 1;



        if (xenstore_read_fe_int(&blkdev->xendev, "ring-ref",

                                 &ring_ref) == -1) {

            return -1;

        }

        blkdev->ring_ref[0] = ring_ref;



    } else if (order >= 0 && order <= MAX_RING_PAGE_ORDER) {

        blkdev->nr_ring_ref = 1 << order;



        for (i = 0; i < blkdev->nr_ring_ref; i++) {

            char *key;



            key = g_strdup_printf("ring-ref%u", i);

            if (!key) {

                return -1;

            }



            if (xenstore_read_fe_int(&blkdev->xendev, key,

                                     &ring_ref) == -1) {

                g_free(key);

                return -1;

            }

            blkdev->ring_ref[i] = ring_ref;



            g_free(key);

        }

    } else {

        xen_pv_printf(xendev, 0, "invalid ring-page-order: %d\n",

                      order);

        return -1;

    }



    if (xenstore_read_fe_int(&blkdev->xendev, "event-channel",

                             &blkdev->xendev.remote_port) == -1) {

        return -1;
@@ -1162,41 +1199,85 @@ static int blk_connect(struct XenDevice *xendev) 
        blkdev->protocol = BLKIF_PROTOCOL_NATIVE;

    }



    blkdev->sring = xengnttab_map_grant_ref(blkdev->xendev.gnttabdev,

                                            blkdev->xendev.dom,

    ring_size = XC_PAGE_SIZE * blkdev->nr_ring_ref;

    switch (blkdev->protocol) {

    case BLKIF_PROTOCOL_NATIVE:

    {

        blkdev->max_requests = __CONST_RING_SIZE(blkif, ring_size);

        break;

    }

    case BLKIF_PROTOCOL_X86_32:

    {

        blkdev->max_requests = __CONST_RING_SIZE(blkif_x86_32, ring_size);

        break;

    }

    case BLKIF_PROTOCOL_X86_64:

    {

        blkdev->max_requests = __CONST_RING_SIZE(blkif_x86_64, ring_size);

        break;

    }

    default:

        return -1;

    }



    /* Calculate the maximum number of grants needed by ioreqs */

    max_grants = MAX_GRANTS(blkdev->max_requests,

                            BLKIF_MAX_SEGMENTS_PER_REQUEST);

    /* Add on the number needed for the ring pages */

    max_grants += blkdev->nr_ring_ref;



    if (xengnttab_set_max_grants(blkdev->xendev.gnttabdev, max_grants)) {

        xen_pv_printf(xendev, 0, "xengnttab_set_max_grants failed: %s\n",

                      strerror(errno));

        return -1;

    }



    domids = g_malloc0_n(blkdev->nr_ring_ref, sizeof(uint32_t));

    for (i = 0; i < blkdev->nr_ring_ref; i++) {

        domids[i] = blkdev->xendev.dom;

    }



    blkdev->sring = xengnttab_map_grant_refs(blkdev->xendev.gnttabdev,

                                             blkdev->nr_ring_ref,

                                             domids,

                                             blkdev->ring_ref,

                                             PROT_READ | PROT_WRITE);



    g_free(domids);



    if (!blkdev->sring) {

        return -1;

    }



    blkdev->cnt_map++;



    switch (blkdev->protocol) {

    case BLKIF_PROTOCOL_NATIVE:

    {

        blkif_sring_t *sring_native = blkdev->sring;

        BACK_RING_INIT(&blkdev->rings.native, sring_native, XC_PAGE_SIZE);

        BACK_RING_INIT(&blkdev->rings.native, sring_native, ring_size);

        break;

    }

    case BLKIF_PROTOCOL_X86_32:

    {

        blkif_x86_32_sring_t *sring_x86_32 = blkdev->sring;



        BACK_RING_INIT(&blkdev->rings.x86_32_part, sring_x86_32, XC_PAGE_SIZE);

        BACK_RING_INIT(&blkdev->rings.x86_32_part, sring_x86_32, ring_size);

        break;

    }

    case BLKIF_PROTOCOL_X86_64:

    {

        blkif_x86_64_sring_t *sring_x86_64 = blkdev->sring;



        BACK_RING_INIT(&blkdev->rings.x86_64_part, sring_x86_64, XC_PAGE_SIZE);

        BACK_RING_INIT(&blkdev->rings.x86_64_part, sring_x86_64, ring_size);

        break;

    }

    }



    if (blkdev->feature_persistent) {

        /* Init persistent grants */

        blkdev->max_grants = max_requests * BLKIF_MAX_SEGMENTS_PER_REQUEST;

        blkdev->max_grants = blkdev->max_requests *

            BLKIF_MAX_SEGMENTS_PER_REQUEST;

        blkdev->persistent_gnts = g_tree_new_full((GCompareDataFunc)int_cmp,

                                             NULL, NULL,

                                             batch_maps ?
@@ -1208,9 +1289,9 @@ static int blk_connect(struct XenDevice *xendev) 


    xen_be_bind_evtchn(&blkdev->xendev);



    xen_pv_printf(&blkdev->xendev, 1, "ok: proto %s, ring-ref %d, "

    xen_pv_printf(&blkdev->xendev, 1, "ok: proto %s, nr-ring-ref %u, "

                  "remote port %d, local port %d\n",

                  blkdev->xendev.protocol, blkdev->ring_ref,

                  blkdev->xendev.protocol, blkdev->nr_ring_ref,

                  blkdev->xendev.remote_port, blkdev->xendev.local_port);

    return 0;

}
@@ -1227,7 +1308,8 @@ static void blk_disconnect(struct XenDevice *xendev) 
    xen_pv_unbind_evtchn(&blkdev->xendev);



    if (blkdev->sring) {

        xengnttab_unmap(blkdev->xendev.gnttabdev, blkdev->sring, 1);

        xengnttab_unmap(blkdev->xendev.gnttabdev, blkdev->sring,

                        blkdev->nr_ring_ref);

        blkdev->cnt_map--;

        blkdev->sring = NULL;

    }