[Xen-changelog] [xen master] blktap2: Use RING_COPY_REQUEST

[patchbot@xxxxxxx]

commit 19f6c522a6a9599317ee1d8c4a155d1400d04c89
Author:     Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
AuthorDate: Fri Nov 20 12:16:02 2015 -0500
Commit:     Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
CommitDate: Fri Dec 18 09:49:43 2015 -0500

    blktap2: Use RING_COPY_REQUEST
    
    Instead of RING_GET_REQUEST. Using a local copy of the
    ring (and also with proper memory barriers) will mean
    we can do not have to worry about the compiler optimizing
    the code and doing a double-fetch in the shared memory space.
    
    This is part of XSA155.
    
    Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 tools/blktap2/drivers/block-log.c   |    3 ++-
 tools/blktap2/drivers/tapdisk-vbd.c |    8 ++++----
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/tools/blktap2/drivers/block-log.c 
b/tools/blktap2/drivers/block-log.c
index 5330cdc..5f3bd35 100644
--- a/tools/blktap2/drivers/block-log.c
+++ b/tools/blktap2/drivers/block-log.c
@@ -494,11 +494,12 @@ static int ctl_kick(struct tdlog_state* s, int fd)
   reqstart = s->bring.req_cons;
   reqend = s->sring->req_prod;
 
+  xen_mb();
   BDPRINTF("ctl: ring kicked (start = %u, end = %u)", reqstart, reqend);
 
   while (reqstart != reqend) {
     /* XXX actually submit these! */
-    memcpy(&req, RING_GET_REQUEST(&s->bring, reqstart), sizeof(req));
+    RING_COPY_REQUEST(&s->bring, reqstart, &req);
     BDPRINTF("ctl: read request %"PRIu64":%u", req.sector, req.count);
     s->bring.req_cons = ++reqstart;
 
diff --git a/tools/blktap2/drivers/tapdisk-vbd.c 
b/tools/blktap2/drivers/tapdisk-vbd.c
index 6d1d94a..89ef9ed 100644
--- a/tools/blktap2/drivers/tapdisk-vbd.c
+++ b/tools/blktap2/drivers/tapdisk-vbd.c
@@ -1555,7 +1555,7 @@ tapdisk_vbd_pull_ring_requests(td_vbd_t *vbd)
        int idx;
        RING_IDX rp, rc;
        td_ring_t *ring;
-       blkif_request_t *req;
+       blkif_request_t req;
        td_vbd_request_t *vreq;
 
        ring = &vbd->ring;
@@ -1566,16 +1566,16 @@ tapdisk_vbd_pull_ring_requests(td_vbd_t *vbd)
        xen_rmb();
 
        for (rc = ring->fe_ring.req_cons; rc != rp; rc++) {
-               req = RING_GET_REQUEST(&ring->fe_ring, rc);
+               RING_COPY_REQUEST(&ring->fe_ring, rc, &req);
                ++ring->fe_ring.req_cons;
 
-               idx  = req->id;
+               idx  = req.id;
                vreq = &vbd->request_list[idx];
 
                ASSERT(list_empty(&vreq->next));
                ASSERT(vreq->secs_pending == 0);
 
-               memcpy(&vreq->req, req, sizeof(blkif_request_t));
+               memcpy(&vreq->req, &req, sizeof(blkif_request_t));
                vbd->received++;
                vreq->vbd = vbd;
 
--
generated by git-patchbot for /home/xen/git/xen.git#master

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