pHyp introduces two different type of credits: Default and Quality
of service (QoS).

The total number of default credits available on each LPAR depends
on CPU resources configured. But these credits can be shared or
over-committed across LPARs in shared mode which can result in
paste command failure (RMA_busy). To avoid NX HW contention, phyp
introduces QoS credit type which makes sure guaranteed access to NX
resources. The system admins can assign QoS credits for each LPAR
via HMC.

Default credit type is used to allocate a VAS window by default as
on powerVM implementation. But the process can pass VAS_WIN_QOS_CREDITS
flag with VAS_TX_WIN_OPEN ioctl to open VAS QoS type window.

Signed-off-by: Haren Myneni <>
 arch/powerpc/include/uapi/asm/vas-api.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/uapi/asm/vas-api.h 
index ebd4b2424785..eb7c8694174f 100644
--- a/arch/powerpc/include/uapi/asm/vas-api.h
+++ b/arch/powerpc/include/uapi/asm/vas-api.h
@@ -13,11 +13,15 @@
 #define VAS_MAGIC      'v'
 #define VAS_TX_WIN_OPEN        _IOW(VAS_MAGIC, 0x20, struct 
+/* Flags to VAS TX open window ioctl */
+/* To allocate a window with QoS credit, otherwise default credit is used */
+#define        VAS_WIN_QOS_CREDITS     0x0000000000000001
 struct vas_tx_win_open_attr {
        __u32   version;
        __s16   vas_id; /* specific instance of vas or -1 for default */
        __u16   reserved1;
-       __u64   flags;  /* Future use */
+       __u64   flags;
        __u64   reserved2[6];

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