[Xen-changelog] [qemu-xen master] xen: slightly simplify bufioreq handling

[patchbot@xxxxxxx]

commit f37f29d31488fe36354e59b2fdc4fae83b2cf763
Author:     Jan Beulich <JBeulich@xxxxxxxx>
AuthorDate: Fri Nov 25 03:06:33 2016 -0700
Commit:     Stefano Stabellini <sstabellini@xxxxxxxxxx>
CommitDate: Mon Nov 28 11:26:04 2016 -0800

    xen: slightly simplify bufioreq handling
    
    There's no point setting fields always receiving the same value on each
    iteration, as handle_ioreq() doesn't alter them anyway. Set state and
    count once ahead of the loop, drop the redundant clearing of
    data_is_ptr, and avoid the meaningless (because count is 1) setting of
    df altogether.
    
    Also avoid doing an unsigned long calculation of size when the field to
    be initialized is only 32 bits wide (and the shift value in the range
    0...3).
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
    Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
    Signed-off-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 xen-hvm.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/xen-hvm.c b/xen-hvm.c
index d74e233..124ae10 100644
--- a/xen-hvm.c
+++ b/xen-hvm.c
@@ -995,6 +995,8 @@ static int handle_buffered_iopage(XenIOState *state)
     }
 
     memset(&req, 0x00, sizeof(req));
+    req.state = STATE_IOREQ_READY;
+    req.count = 1;
 
     for (;;) {
         uint32_t rdptr = buf_page->read_pointer, wrptr;
@@ -1009,15 +1011,11 @@ static int handle_buffered_iopage(XenIOState *state)
             break;
         }
         buf_req = &buf_page->buf_ioreq[rdptr % IOREQ_BUFFER_SLOT_NUM];
-        req.size = 1UL << buf_req->size;
-        req.count = 1;
+        req.size = 1U << buf_req->size;
         req.addr = buf_req->addr;
         req.data = buf_req->data;
-        req.state = STATE_IOREQ_READY;
         req.dir = buf_req->dir;
-        req.df = 1;
         req.type = buf_req->type;
-        req.data_is_ptr = 0;
         xen_rmb();
         qw = (req.size == 8);
         if (qw) {
@@ -1032,6 +1030,13 @@ static int handle_buffered_iopage(XenIOState *state)
 
         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.
+         */
+        assert(req.state == STATE_IOREQ_READY);
+        assert(req.count == 1);
+        assert(!req.data_is_ptr);
+
         atomic_add(&buf_page->read_pointer, qw + 1);
     }
 
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#master

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