On Wed, Nov 26, 2014 at 03:54:40PM +0100, Cornelia Huck wrote: > On Wed, 26 Nov 2014 16:44:00 +0200 > "Michael S. Tsirkin" <m...@redhat.com> wrote: > > > On Wed, Nov 26, 2014 at 03:31:02PM +0100, Cornelia Huck wrote: > > > On Tue, 25 Nov 2014 18:43:14 +0200 > > > "Michael S. Tsirkin" <m...@redhat.com> wrote: > > > > > > > We use native endian-ness internally but never > > > > expose it to guest. > > > > > > > > Signed-off-by: Michael S. Tsirkin <m...@redhat.com> > > > > --- > > > > drivers/vhost/net.c | 10 +++++----- > > > > 1 file changed, 5 insertions(+), 5 deletions(-) > > > > > > > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > > > > index 8dae2f7..dce5c58 100644 > > > > --- a/drivers/vhost/net.c > > > > +++ b/drivers/vhost/net.c > > > > @@ -48,15 +48,15 @@ MODULE_PARM_DESC(experimental_zcopytx, "Enable Zero > > > > Copy TX;" > > > > * status internally; used for zerocopy tx only. > > > > */ > > > > /* Lower device DMA failed */ > > > > -#define VHOST_DMA_FAILED_LEN 3 > > > > +#define VHOST_DMA_FAILED_LEN ((__force __virtio32)3) > > > > /* Lower device DMA done */ > > > > -#define VHOST_DMA_DONE_LEN 2 > > > > +#define VHOST_DMA_DONE_LEN ((__force __virtio32)2) > > > > /* Lower device DMA in progress */ > > > > -#define VHOST_DMA_IN_PROGRESS 1 > > > > +#define VHOST_DMA_IN_PROGRESS ((__force __virtio32)1) > > > > /* Buffer unused */ > > > > -#define VHOST_DMA_CLEAR_LEN 0 > > > > +#define VHOST_DMA_CLEAR_LEN ((__force __virtio32)0) > > > > > > I find these constants a bit confusing: What does __virtio32 mean > > > without the context of a vq or device? > > > > > > > > > > > -#define VHOST_DMA_IS_DONE(len) ((len) >= VHOST_DMA_DONE_LEN) > > > > +#define VHOST_DMA_IS_DONE(len) ((__force u32)(len) >= (__force > > > > u32)VHOST_DMA_DONE_LEN) > > > > > > And here you cast it to a plain u32 again. > > > > > > I looked at the final code, and you seem either to use the above > > > constants for .len or do a cpu_to_vhost32(). Wouldn't you need to > > > convert the constants as well? > > > > I tried to explain it in the commit message. > > It's a hack in vhost: it keeps virtio used structure in host > > memory, but abuses length field for internal housekeeping. > > This works because length in used ring for tx is always 0. > > Ah, ok. It might make sense to add this explanation to the patch :)
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