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Commit 5bb0c9be authored by Michael S. Tsirkin's avatar Michael S. Tsirkin
Browse files

xenbus: use virt_xxx barriers 



drivers/xen/xenbus/xenbus_comms.c uses
full memory barriers to communicate with the other side.

For guests compiled with CONFIG_SMP, smp_wmb and smp_mb
would be sufficient, so mb() and wmb() here are only needed if
a non-SMP guest runs on an SMP host.

Switch to virt_xxx barriers which serve this exact purpose.

Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Acked-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
parent 788e5b3a

drivers/xen/xenbus/xenbus_comms.c

+4 −4
Original line number Diff line number Diff line
@@ -123,14 +123,14 @@ int xb_write(const void *data, unsigned len) 
			avail = len;



		/* Must write data /after/ reading the consumer index. */

		mb();

		virt_mb();



		memcpy(dst, data, avail);

		data += avail;

		len -= avail;



		/* Other side must not see new producer until data is there. */

		wmb();

		virt_wmb();

		intf->req_prod += avail;



		/* Implies mb(): other side will see the updated producer. */
@@ -180,14 +180,14 @@ int xb_read(void *data, unsigned len) 
			avail = len;



		/* Must read data /after/ reading the producer index. */

		rmb();

		virt_rmb();



		memcpy(data, src, avail);

		data += avail;

		len -= avail;



		/* Other side must not see free space until we've copied out */

		mb();

		virt_mb();

		intf->rsp_cons += avail;



		pr_debug("Finished read of %i bytes (%i to go)\n", avail, len);