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Re: [Qemu-devel] [PATCH v2 2/2] xen: dont try setting max grants multipl
From: |
Anthony PERARD |
Subject: |
Re: [Qemu-devel] [PATCH v2 2/2] xen: dont try setting max grants multiple times |
Date: |
Mon, 25 Sep 2017 15:41:34 +0100 |
User-agent: |
Mutt/1.9.0 (2017-09-02) |
On Fri, Sep 22, 2017 at 02:07:25PM +0200, Juergen Gross wrote:
> Trying to call xengnttab_set_max_grants() with the same file handle
> might fail on some kernels, as this operation is allowed only once.
>
> This is a problem for the qdisk backend as blk_connect() can be
> called multiple times for a domain, e.g. in case grub-xen is being
> used to boot it.
>
> So instead of letting the generic backend code open the gnttab device
> do it in blk_connect() and close it again in blk_disconnect.
>
> Signed-off-by: Juergen Gross <address@hidden>
Acked-by: Anthony PERARD <address@hidden>
Thanks.
> ---
> V2:
> - always call blk_disconnect() from blk_free() in order to have the
> gnttab device node closed (Anthony Perard)
> ---
> hw/block/xen_disk.c | 16 ++++++++++++----
> 1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
> index 62506e3167..e431bd89e8 100644
> --- a/hw/block/xen_disk.c
> +++ b/hw/block/xen_disk.c
> @@ -1220,6 +1220,12 @@ static int blk_connect(struct XenDevice *xendev)
> /* Add on the number needed for the ring pages */
> max_grants += blkdev->nr_ring_ref;
>
> + blkdev->xendev.gnttabdev = xengnttab_open(NULL, 0);
> + if (blkdev->xendev.gnttabdev == NULL) {
> + xen_pv_printf(xendev, 0, "xengnttab_open failed: %s\n",
> + strerror(errno));
> + return -1;
> + }
> if (xengnttab_set_max_grants(blkdev->xendev.gnttabdev, max_grants)) {
> xen_pv_printf(xendev, 0, "xengnttab_set_max_grants failed: %s\n",
> strerror(errno));
> @@ -1327,6 +1333,11 @@ static void blk_disconnect(struct XenDevice *xendev)
> }
> blkdev->feature_persistent = false;
> }
> +
> + if (blkdev->xendev.gnttabdev) {
> + xengnttab_close(blkdev->xendev.gnttabdev);
> + blkdev->xendev.gnttabdev = NULL;
> + }
> }
>
> static int blk_free(struct XenDevice *xendev)
> @@ -1334,9 +1345,7 @@ static int blk_free(struct XenDevice *xendev)
> struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev,
> xendev);
> struct ioreq *ioreq;
>
> - if (blkdev->blk || blkdev->sring) {
> - blk_disconnect(xendev);
> - }
> + blk_disconnect(xendev);
>
> while (!QLIST_EMPTY(&blkdev->freelist)) {
> ioreq = QLIST_FIRST(&blkdev->freelist);
> @@ -1363,7 +1372,6 @@ static void blk_event(struct XenDevice *xendev)
>
> struct XenDevOps xen_blkdev_ops = {
> .size = sizeof(struct XenBlkDev),
> - .flags = DEVOPS_FLAG_NEED_GNTDEV,
> .alloc = blk_alloc,
> .init = blk_init,
> .initialise = blk_connect,
> --
> 2.12.3
>
--
Anthony PERARD