Commit 2bcd05cf authored by Paul Durrant's avatar Paul Durrant Committed by Anthony PERARD
Browse files

xen-block: scale sector based quantities correctly 



The Xen blkif protocol requires that sector based quantities should be
interpreted strictly as multiples of 512 bytes. Specifically:

"first_sect and last_sect in blkif_request_segment, as well as
sector_number in blkif_request, are always expressed in 512-byte units."

Commit fcab2b46 "xen: add header and build dataplane/xen-block.c"
incorrectly modified behaviour to use the block device logical_block_size
property as the scale, instead of correctly shifting values by the
hardcoded BDRV_SECTOR_BITS (and hence scaling them to 512 byte units).
This patch undoes that change and restores compliance with the spec.

Furthermore, this patch also restores the original xen_disk behaviour
of advertizing a hardcoded 'sector-size' value of 512 in xenstore and
scaling 'sectors' accordingly. The realize() method is also modified to
fail if logical_block_size is set to anything other than 512.

Signed-off-by: default avatarPaul Durrant <paul.durrant@citrix.com>
Reviewed-by: default avatarAnthony PERARD <anthony.perard@citrix.com>
Message-Id: <20190401121719.27208-1-paul.durrant@citrix.com>
Signed-off-by: default avatarAnthony PERARD <anthony.perard@citrix.com>
parent 15f08450

hw/block/dataplane/xen-block.c

+13 −15
Original line number Diff line number Diff line
@@ -49,7 +49,6 @@ struct XenBlockDataPlane { 
    unsigned int *ring_ref;

    unsigned int nr_ring_ref;

    void *sring;

    int64_t file_blk;

    int protocol;

    blkif_back_rings_t rings;

    int more_work;
@@ -168,7 +167,7 @@ static int xen_block_parse_request(XenBlockRequest *request) 
        goto err;

    }



    request->start = request->req.sector_number * dataplane->file_blk;

    request->start = request->req.sector_number * XEN_BLKIF_SECTOR_SIZE;

    for (i = 0; i < request->req.nr_segments; i++) {

        if (i == BLKIF_MAX_SEGMENTS_PER_REQUEST) {

            error_report("error: nr_segments too big");
@@ -178,14 +177,14 @@ static int xen_block_parse_request(XenBlockRequest *request) 
            error_report("error: first > last sector");

            goto err;

        }

        if (request->req.seg[i].last_sect * dataplane->file_blk >=

        if (request->req.seg[i].last_sect * XEN_BLKIF_SECTOR_SIZE >=

            XC_PAGE_SIZE) {

            error_report("error: page crossing");

            goto err;

        }



        len = (request->req.seg[i].last_sect -

               request->req.seg[i].first_sect + 1) * dataplane->file_blk;

               request->req.seg[i].first_sect + 1) * XEN_BLKIF_SECTOR_SIZE;

        request->size += len;

    }

    if (request->start + request->size > blk_getlength(dataplane->blk)) {
@@ -205,7 +204,6 @@ static int xen_block_copy_request(XenBlockRequest *request) 
    XenDevice *xendev = dataplane->xendev;

    XenDeviceGrantCopySegment segs[BLKIF_MAX_SEGMENTS_PER_REQUEST];

    int i, count;

    int64_t file_blk = dataplane->file_blk;

    bool to_domain = (request->req.operation == BLKIF_OP_READ);

    void *virt = request->buf;

    Error *local_err = NULL;
@@ -220,16 +218,17 @@ static int xen_block_copy_request(XenBlockRequest *request) 
        if (to_domain) {

            segs[i].dest.foreign.ref = request->req.seg[i].gref;

            segs[i].dest.foreign.offset = request->req.seg[i].first_sect *

                file_blk;

                XEN_BLKIF_SECTOR_SIZE;

            segs[i].source.virt = virt;

        } else {

            segs[i].source.foreign.ref = request->req.seg[i].gref;

            segs[i].source.foreign.offset = request->req.seg[i].first_sect *

                file_blk;

                XEN_BLKIF_SECTOR_SIZE;

            segs[i].dest.virt = virt;

        }

        segs[i].len = (request->req.seg[i].last_sect -

                       request->req.seg[i].first_sect + 1) * file_blk;

                       request->req.seg[i].first_sect + 1) *

                      XEN_BLKIF_SECTOR_SIZE;

        virt += segs[i].len;

    }
@@ -331,22 +330,22 @@ static bool xen_block_split_discard(XenBlockRequest *request, 
    XenBlockDataPlane *dataplane = request->dataplane;

    int64_t byte_offset;

    int byte_chunk;

    uint64_t byte_remaining, limit;

    uint64_t byte_remaining;

    uint64_t sec_start = sector_number;

    uint64_t sec_count = nr_sectors;



    /* Wrap around, or overflowing byte limit? */

    if (sec_start + sec_count < sec_count ||

        sec_start + sec_count > INT64_MAX / dataplane->file_blk) {

        sec_start + sec_count > INT64_MAX / XEN_BLKIF_SECTOR_SIZE) {

        return false;

    }



    limit = BDRV_REQUEST_MAX_SECTORS * dataplane->file_blk;

    byte_offset = sec_start * dataplane->file_blk;

    byte_remaining = sec_count * dataplane->file_blk;

    byte_offset = sec_start * XEN_BLKIF_SECTOR_SIZE;

    byte_remaining = sec_count * XEN_BLKIF_SECTOR_SIZE;



    do {

        byte_chunk = byte_remaining > limit ? limit : byte_remaining;

        byte_chunk = byte_remaining > BDRV_REQUEST_MAX_BYTES ?

            BDRV_REQUEST_MAX_BYTES : byte_remaining;

        request->aio_inflight++;

        blk_aio_pdiscard(dataplane->blk, byte_offset, byte_chunk,

                         xen_block_complete_aio, request);
@@ -632,7 +631,6 @@ XenBlockDataPlane *xen_block_dataplane_create(XenDevice *xendev, 
    XenBlockDataPlane *dataplane = g_new0(XenBlockDataPlane, 1);



    dataplane->xendev = xendev;

    dataplane->file_blk = conf->logical_block_size;

    dataplane->blk = conf->blk;



    QLIST_INIT(&dataplane->inflight);

hw/block/xen-block.c

+8 −2
Original line number Diff line number Diff line
@@ -149,7 +149,7 @@ static void xen_block_set_size(XenBlockDevice *blockdev) 
    const char *type = object_get_typename(OBJECT(blockdev));

    XenBlockVdev *vdev = &blockdev->props.vdev;

    BlockConf *conf = &blockdev->props.conf;

    int64_t sectors = blk_getlength(conf->blk) / conf->logical_block_size;

    int64_t sectors = blk_getlength(conf->blk) / XEN_BLKIF_SECTOR_SIZE;

    XenDevice *xendev = XEN_DEVICE(blockdev);



    trace_xen_block_size(type, vdev->disk, vdev->partition, sectors);
@@ -223,6 +223,12 @@ static void xen_block_realize(XenDevice *xendev, Error **errp) 


    blkconf_blocksizes(conf);



    if (conf->logical_block_size != XEN_BLKIF_SECTOR_SIZE) {

        error_setg(errp, "logical_block_size != %u not supported",

                   XEN_BLKIF_SECTOR_SIZE);

        return;

    }



    if (conf->logical_block_size > conf->physical_block_size) {

        error_setg(

            errp, "logical_block_size > physical_block_size not supported");
@@ -253,7 +259,7 @@ static void xen_block_realize(XenDevice *xendev, Error **errp) 
                               blockdev->device_type);



    xen_device_backend_printf(xendev, "sector-size", "%u",

                              conf->logical_block_size);

                              XEN_BLKIF_SECTOR_SIZE);



    xen_block_set_size(blockdev);

hw/block/xen_blkif.h

+2 −0
Original line number Diff line number Diff line
@@ -143,4 +143,6 @@ static inline void blkif_get_x86_64_req(blkif_request_t *dst, 
    }

}



#define XEN_BLKIF_SECTOR_SIZE 512



#endif /* XEN_BLKIF_H */