Re: [Qemu-devel] [PATCH 3/3] xen: ignore direction in bufioreq handling

[Paul Durrant]

> -----Original Message-----
> From: Jan Beulich [mailto:address@hidden
> Sent: 23 November 2016 09:25
> To: address@hidden
> Cc: Anthony Perard <address@hidden>; Paul Durrant
> <address@hidden>; Stefano Stabellini <address@hidden>; xen-
> devel <address@hidden>
> Subject: [PATCH 3/3] xen: ignore direction in bufioreq handling
> 
> There's no way to communicate back read data, so only writes can ever
> be usefully specified. Ignore the field, paving the road for eventually
> re-using the bit for something else in a few (many?) years time.
> 
> Signed-off-by: Jan Beulich <address@hidden>

Reviewed-by: Paul Durrant <address@hidden>

> 
> --- a/xen-hvm.c
> +++ b/xen-hvm.c
> @@ -997,6 +997,7 @@ static int handle_buffered_iopage(XenIOS
>      memset(&req, 0x00, sizeof(req));
>      req.state = STATE_IOREQ_READY;
>      req.count = 1;
> +    req.dir = IOREQ_WRITE;
> 
>      for (;;) {
>          uint32_t rdptr = buf_page->read_pointer, wrptr;
> @@ -1014,7 +1015,6 @@ static int handle_buffered_iopage(XenIOS
>          req.size = 1U << buf_req->size;
>          req.addr = buf_req->addr;
>          req.data = buf_req->data;
> -        req.dir = buf_req->dir;
>          req.type = buf_req->type;
>          xen_rmb();
>          qw = (req.size == 8);
> @@ -1031,10 +1031,12 @@ static int handle_buffered_iopage(XenIOS
>          handle_ioreq(state, &req);
> 
>          /* Only req.data may get updated by handle_ioreq(), albeit even that
> -         * should not happen as such data would never make it to the guest.
> +         * should not happen as such data would never make it to the guest 
> (we
> +         * can only usefully see writes here after all).
>           */
>          assert(req.state == STATE_IOREQ_READY);
>          assert(req.count == 1);
> +        assert(req.dir == IOREQ_WRITE);
>          assert(!req.data_is_ptr);
> 
>          atomic_add(&buf_page->read_pointer, qw + 1);
> 
>