linux-kernel - [PATCH 3/4] xen/interface: don't discard pending work in FRONT/BACK_RING

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Date:   Thu, 5 Dec 2019 14:01:22 +0000
From:   Paul Durrant <pdurrant@...zon.com>
To:     <linux-kernel@...r.kernel.org>, <xen-devel@...ts.xenproject.org>
CC:     Paul Durrant <pdurrant@...zon.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        "Stefano Stabellini" <sstabellini@...nel.org>
Subject: [PATCH 3/4] xen/interface: don't discard pending work in FRONT/BACK_RING_ATTACH

Currently these macros will skip over any requests/responses that are
added to the shared ring whilst it is detached. This, in general, is not
a desirable semantic since most frontend implementations will eventually
block waiting for a response which would either never appear or never be
processed.

NOTE: These macros are currently unused. BACK_RING_ATTACH(), however, will
      be used in a subsequent patch.

Signed-off-by: Paul Durrant <pdurrant@...zon.com>
---
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: Stefano Stabellini <sstabellini@...nel.org>
---
 include/xen/interface/io/ring.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/xen/interface/io/ring.h b/include/xen/interface/io/ring.h
index 3f40501fc60b..405adfed87e6 100644
--- a/include/xen/interface/io/ring.h
+++ b/include/xen/interface/io/ring.h
@@ -143,14 +143,14 @@ struct __name##_back_ring {						\
 #define FRONT_RING_ATTACH(_r, _s, __size) do {				\
     (_r)->sring = (_s);							\
     (_r)->req_prod_pvt = (_s)->req_prod;				\
-    (_r)->rsp_cons = (_s)->rsp_prod;					\
+    (_r)->rsp_cons = (_s)->req_prod;					\
     (_r)->nr_ents = __RING_SIZE(_s, __size);				\
 } while (0)
 
 #define BACK_RING_ATTACH(_r, _s, __size) do {				\
     (_r)->sring = (_s);							\
     (_r)->rsp_prod_pvt = (_s)->rsp_prod;				\
-    (_r)->req_cons = (_s)->req_prod;					\
+    (_r)->req_cons = (_s)->rsp_prod;					\
     (_r)->nr_ents = __RING_SIZE(_s, __size);				\
 } while (0)
 
-- 
2.20.1