> -----Original Message-----
> From: Paul Durrant [mailto:[email protected]]
> Sent: 04 May 2018 14:56
> To: [email protected]; [email protected]; qemu-
> [email protected]
> Cc: Paul Durrant <[email protected]>; Stefano Stabellini
> <[email protected]>; Anthony Perard <[email protected]>;
> Kevin Wolf <[email protected]>; Max Reitz <[email protected]>
> Subject: [PATCH v2 7/8] xen_disk: use a single entry iovec
>
> Since xen_disk now always copies data to and from a guest there is no need
> to maintain a vector entry corresponding to every page of a request.
> This means there is less per-request state to maintain so the ioreq
> structure can shrink significantly.
>
> Signed-off-by: Paul Durrant <[email protected]>
> ---
> Cc: Stefano Stabellini <[email protected]>
> Cc: Anthony Perard <[email protected]>
> Cc: Kevin Wolf <[email protected]>
> Cc: Max Reitz <[email protected]>
>
> v2:
> - Re-based
Unfortunately I managed to drop a hunk during rebase and so this patch is
actually broken. I'll send a rectified v3 shortly.
Paul
> ---
> hw/block/xen_disk.c | 71
> ++++++++++++++---------------------------------------
> 1 file changed, 18 insertions(+), 53 deletions(-)
>
> diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
> index 28be8b6..230961f 100644
> --- a/hw/block/xen_disk.c
> +++ b/hw/block/xen_disk.c
> @@ -46,13 +46,10 @@ struct ioreq {
> /* parsed request */
> off_t start;
> QEMUIOVector v;
> + void *buf;
> + size_t size;
> int presync;
>
> - /* grant mapping */
> - uint32_t refs[BLKIF_MAX_SEGMENTS_PER_REQUEST];
> - void *page[BLKIF_MAX_SEGMENTS_PER_REQUEST];
> - void *pages;
> -
> /* aio status */
> int aio_inflight;
> int aio_errors;
> @@ -110,12 +107,10 @@ static void ioreq_reset(struct ioreq *ioreq)
> memset(&ioreq->req, 0, sizeof(ioreq->req));
> ioreq->status = 0;
> ioreq->start = 0;
> + ioreq->buf = NULL;
> + ioreq->size = 0;
> ioreq->presync = 0;
>
> - memset(ioreq->refs, 0, sizeof(ioreq->refs));
> - memset(ioreq->page, 0, sizeof(ioreq->page));
> - ioreq->pages = NULL;
> -
> ioreq->aio_inflight = 0;
> ioreq->aio_errors = 0;
>
> @@ -138,7 +133,7 @@ static struct ioreq *ioreq_start(struct XenBlkDev
> *blkdev)
> ioreq = g_malloc0(sizeof(*ioreq));
> ioreq->blkdev = blkdev;
> blkdev->requests_total++;
> - qemu_iovec_init(&ioreq->v, BLKIF_MAX_SEGMENTS_PER_REQUEST);
> + qemu_iovec_init(&ioreq->v, 1);
> } else {
> /* get one from freelist */
> ioreq = QLIST_FIRST(&blkdev->freelist);
> @@ -183,7 +178,6 @@ static void ioreq_release(struct ioreq *ioreq, bool
> finish)
> static int ioreq_parse(struct ioreq *ioreq)
> {
> struct XenBlkDev *blkdev = ioreq->blkdev;
> - uintptr_t mem;
> size_t len;
> int i;
>
> @@ -230,13 +224,10 @@ static int ioreq_parse(struct ioreq *ioreq)
> goto err;
> }
>
> - ioreq->refs[i] = ioreq->req.seg[i].gref;
> -
> - mem = ioreq->req.seg[i].first_sect * blkdev->file_blk;
> len = (ioreq->req.seg[i].last_sect - ioreq->req.seg[i].first_sect +
> 1) *
> blkdev->file_blk;
> - qemu_iovec_add(&ioreq->v, (void*)mem, len);
> + ioreq->size += len;
> }
> - if (ioreq->start + ioreq->v.size > blkdev->file_size) {
> + if (ioreq->start + ioreq->size > blkdev->file_size) {
> xen_pv_printf(&blkdev->xendev, 0, "error: access beyond end of
> file\n");
> goto err;
> }
> @@ -247,35 +238,6 @@ err:
> return -1;
> }
>
> -static void ioreq_free_copy_buffers(struct ioreq *ioreq)
> -{
> - int i;
> -
> - for (i = 0; i < ioreq->v.niov; i++) {
> - ioreq->page[i] = NULL;
> - }
> -
> - qemu_vfree(ioreq->pages);
> -}
> -
> -static int ioreq_init_copy_buffers(struct ioreq *ioreq)
> -{
> - int i;
> -
> - if (ioreq->v.niov == 0) {
> - return 0;
> - }
> -
> - ioreq->pages = qemu_memalign(XC_PAGE_SIZE, ioreq->v.niov *
> XC_PAGE_SIZE);
> -
> - for (i = 0; i < ioreq->v.niov; i++) {
> - ioreq->page[i] = ioreq->pages + i * XC_PAGE_SIZE;
> - ioreq->v.iov[i].iov_base = ioreq->page[i];
> - }
> -
> - return 0;
> -}
> -
> static int ioreq_grant_copy(struct ioreq *ioreq)
> {
> struct XenBlkDev *blkdev = ioreq->blkdev;
> @@ -284,6 +246,7 @@ static int ioreq_grant_copy(struct ioreq *ioreq)
> int i, count, rc;
> int64_t file_blk = ioreq->blkdev->file_blk;
> bool to_domain = (ioreq->req.operation == BLKIF_OP_READ);
> + void *virt = ioreq->buf;
>
> if (ioreq->v.niov == 0) {
> return 0;
> @@ -293,16 +256,17 @@ static int ioreq_grant_copy(struct ioreq *ioreq)
>
> for (i = 0; i < count; i++) {
> if (to_domain) {
> - segs[i].dest.foreign.ref = ioreq->refs[i];
> + segs[i].dest.foreign.ref = ioreq->req.seg[i].gref;
> segs[i].dest.foreign.offset = ioreq->req.seg[i].first_sect *
> file_blk;
> - segs[i].source.virt = ioreq->v.iov[i].iov_base;
> + segs[i].source.virt = virt;
> } else {
> - segs[i].source.foreign.ref = ioreq->refs[i];
> + segs[i].source.foreign.ref = ioreq->req.seg[i].gref;
> segs[i].source.foreign.offset = ioreq->req.seg[i].first_sect *
> file_blk;
> - segs[i].dest.virt = ioreq->v.iov[i].iov_base;
> + segs[i].dest.virt = virt;
> }
> segs[i].len = (ioreq->req.seg[i].last_sect
> - ioreq->req.seg[i].first_sect + 1) * file_blk;
> + virt += segs[i].len;
> }
>
> rc = xen_be_copy_grant_refs(xendev, to_domain, segs, count);
> @@ -314,6 +278,7 @@ static int ioreq_grant_copy(struct ioreq *ioreq)
> return -1;
> }
>
> + qemu_iovec_add(&ioreq->v, ioreq->buf, ioreq->size);
> return rc;
> }
>
> @@ -348,14 +313,14 @@ static void qemu_aio_complete(void *opaque, int
> ret)
> if (ret == 0) {
> ioreq_grant_copy(ioreq);
> }
> - ioreq_free_copy_buffers(ioreq);
> + qemu_vfree(ioreq->buf);
> break;
> case BLKIF_OP_WRITE:
> case BLKIF_OP_FLUSH_DISKCACHE:
> if (!ioreq->req.nr_segments) {
> break;
> }
> - ioreq_free_copy_buffers(ioreq);
> + qemu_vfree(ioreq->buf);
> break;
> default:
> break;
> @@ -423,12 +388,12 @@ static int ioreq_runio_qemu_aio(struct ioreq
> *ioreq)
> {
> struct XenBlkDev *blkdev = ioreq->blkdev;
>
> - ioreq_init_copy_buffers(ioreq);
> + ioreq->buf = qemu_memalign(XC_PAGE_SIZE, ioreq->size);
> if (ioreq->req.nr_segments &&
> (ioreq->req.operation == BLKIF_OP_WRITE ||
> ioreq->req.operation == BLKIF_OP_FLUSH_DISKCACHE) &&
> ioreq_grant_copy(ioreq)) {
> - ioreq_free_copy_buffers(ioreq);
> + qemu_vfree(ioreq->buf);
> goto err;
> }
>
> --
> 2.1.4
