[PATCH] s390: qdio V=V pass-through

New feature V=V qdio pass-through.

QDIO and HiperSockets processing in z/VM V=V guest environments (as well as
V=R with z/VM running in LPAR mode) requires shadowing of all QDIO
architecture queue elements.  Especially the shadowing of SBALs and SLSBs
structures in the hypervisor, and the need to issue SIGA SYNC operations to
observe state changes, eventually causes significant CPU processing overhead
in the hypervisor.

The QDIO pass-through support for V=V guests avoids the shadowing of SBALs and
SLSBs.  This significantly reduces the hypervisor overhead for QDIO based I/O.

Signed-off-by: Frank Pavlic <pavlic@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 3 deletions

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 477ac2758bd5..1846fbfd6bf2 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -240,8 +240,8 @@ config MACHCHK_WARNING
 config QDIO
         tristate "QDIO support"
         ---help---
-          This driver provides the Queued Direct I/O base support for the
-          IBM S/390 (G5 and G6) and eServer zSeries (z800, z890, z900 and z990).
+          This driver provides the Queued Direct I/O base support for
+          IBM mainframes.
 
           For details please refer to the documentation provided by IBM at
           <http://www10.software.ibm.com/developerworks/opensource/linux390>
@@ -263,7 +263,8 @@ config QDIO_DEBUG
         bool "Extended debugging information"
         depends on QDIO
         help
-          Say Y here to get extended debugging output in /proc/s390dbf/qdio...
+          Say Y here to get extended debugging output in
+            /sys/kernel/debug/s390dbf/qdio...
           Warning: this option reduces the performance of the QDIO module.
 
           If unsure, say N.