We should not consume the second slot if it didn't get written yet.
Normal writers - i.e. Xen - would not update write_pointer between the
two writes, but the page may get fiddled with by the guest itself, and
we're better off avoiding to enter an infinite loop in that case.
Reported-by: yanghongke <yanghon...@huawei.com>
Signed-off-by: Jan Beulich <jbeul...@suse.com>
---
v2: Bail (using hw_error()) instead of just breaking the loop.
--- a/xen-hvm.c
+++ b/xen-hvm.c
@@ -1021,6 +1021,9 @@ static int handle_buffered_iopage(XenIOS
xen_rmb();
qw = (req.size == 8);
if (qw) {
+ if (rdptr + 1 == wrptr) {
+ hw_error("Incomplete quad word buffered ioreq");
+ }
buf_req = &buf_page->buf_ioreq[(rdptr + 1) %
IOREQ_BUFFER_SLOT_NUM];
req.data |= ((uint64_t)buf_req->data) << 32;
