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powerpc/pseries: Fix dedicated processor partition detection

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commit f13c13a005 (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 <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Anton Blanchard 2013-10-20 10:26:20 +11:00 committed by Benjamin Herrenschmidt
parent dbc2fbd7c2
commit 733187e295
1 changed files with 6 additions and 6 deletions
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12
arch/powerpc/include/asm/lppaca.h
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@ -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);
}
/*