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Re: [Qemu-block] [PATCH] xen-block: scale sector based quantities correc
Re: [Qemu-block] [PATCH] xen-block: scale sector based quantities correctly
Thu, 21 Mar 2019 15:02:47 +0000
> -----Original Message-----
> From: Anthony PERARD [mailto:address@hidden
> Sent: 21 March 2019 15:00
> To: Paul Durrant <address@hidden>
> Cc: address@hidden; address@hidden; address@hidden; Stefan Hajnoczi
> <address@hidden>; Stefano Stabellini <address@hidden>; Kevin Wolf
> <address@hidden>; Max
> Reitz <address@hidden>
> Subject: Re: [PATCH] xen-block: scale sector based quantities correctly
> On Wed, Mar 20, 2019 at 04:26:32PM +0000, Paul Durrant wrote:
> > The mail thread at  clarifies that the Xen blkif protocol requires that
> > sector based quantities should be interpreted strictly as multiples of
> > 512 bytes. This patch modifies the xen-block code accordingly.
> > 
> > https://lists.xenproject.org/archives/html/xen-devel/2019-03/msg01600.html
> So, that patch  only makes one change: how to interpret the "sectors"
> node. It doesn't change the unit of a sector in blkif_request and
> For a request, there is a comment in blkif.h:
> NB. first_sect and last_sect in blkif_request_segment, as well as
> sector_number in blkif_request, are always expressed in 512-byte units.
> I think most of this QEMU patch is to comply with that comment and would
> be a bug fix, but the single line change in hw/block/xen-block.c is
> > diff --git a/hw/block/xen-block.c b/hw/block/xen-block.c
> > index a848849f48..57e9da7e1c 100644
> > --- a/hw/block/xen-block.c
> > +++ b/hw/block/xen-block.c
> > @@ -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;
> That the only thing that the thread  is changing.
Ok, true. I'll split this up into two patches then.
> > XenDevice *xendev = XEN_DEVICE(blockdev);
> > trace_xen_block_size(type, vdev->disk, vdev->partition, sectors);
> Anthony PERARD