From 733187e29576041ceccf3b82092ca900fc929170 Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Sun, 20 Oct 2013 10:26:20 +1100 Subject: [PATCH] powerpc/pseries: Fix dedicated processor partition detection commit f13c13a00512 (powerpc: Stop using non-architected shared_proc field in lppaca) fixed a potential issue with shared/dedicated partition detection. The old method of detection relied on an unarchitected field (shared_proc), and this patch switched to using something architected (a non zero yield_count). Unfortunately the assertion in the Linux header that yield_count is only non zero on shared processor partitions is not true. It turns out dedicated processor partitions can increment yield_count and as such we falsely detect dedicated partitions as shared. Fix the comment, and switch back to using the old method. Signed-off-by: Anton Blanchard Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/include/asm/lppaca.h | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/arch/powerpc/include/asm/lppaca.h b/arch/powerpc/include/asm/lppaca.h index 4470d1e..844c28d 100644 --- a/arch/powerpc/include/asm/lppaca.h +++ b/arch/powerpc/include/asm/lppaca.h @@ -84,8 +84,8 @@ struct lppaca { * the processor is yielded (either because of an OS yield or a * hypervisor preempt). An even value implies that the processor is * currently executing. - * NOTE: This value will ALWAYS be zero for dedicated processors and - * will NEVER be zero for shared processors (ie, initialized to a 1). + * NOTE: Even dedicated processor partitions can yield so this + * field cannot be used to determine if we are shared or dedicated. */ volatile __be32 yield_count; volatile __be32 dispersion_count; /* dispatch changed physical cpu */ @@ -106,15 +106,15 @@ extern struct lppaca lppaca[]; #define lppaca_of(cpu) (*paca[cpu].lppaca_ptr) /* - * Old kernels used a reserved bit in the VPA to determine if it was running - * in shared processor mode. New kernels look for a non zero yield count - * but KVM still needs to set the bit to keep the old stuff happy. + * We are using a non architected field to determine if a partition is + * shared or dedicated. This currently works on both KVM and PHYP, but + * we will have to transition to something better. */ #define LPPACA_OLD_SHARED_PROC 2 static inline bool lppaca_shared_proc(struct lppaca *l) { - return l->yield_count != 0; + return !!(l->__old_status & LPPACA_OLD_SHARED_PROC); } /* -- 2.7.4