[PATCH 2/3] PPC: PMC: Set pmcregs_in_use in paca when running as LPAR

Suraj Jitindar Singh sjitindarsingh at gmail.com
Wed Jul 3 11:20:21 AEST 2019

The ability to run nested guests under KVM means that a guest can also
act as a hypervisor for it's own nested guest. Currently
ppc_set_pmu_inuse() assumes that either FW_FEATURE_LPAR is set,
indicating a guest environment, and so sets the pmcregs_in_use flag in
the lppaca, or that it isn't set, indicating a hypervisor environment,
and so sets the pmcregs_in_use flag in the paca.

The pmcregs_in_use flag in the lppaca is used to communicate this
information to a hypervisor and so must be set in a guest environment.
The pmcregs_in_use flag in the paca is used by KVM code to determine
whether the host state of the performance monitoring unit (PMU) must be
saved and restored when running a guest.

Thus when a guest also acts as a hypervisor it must set this bit in both
places since it needs to ensure both that the real hypervisor saves it's
pmu registers when it runs (requires pmcregs_in_use flag in lppaca), and
that it saves it's own pmu registers when running a nested guest
(requires pmcregs_in_use flag in paca).

Modify ppc_set_pmu_inuse() so that the pmcregs_in_use bit is set in both
the lppaca and the paca when a guest (LPAR) is running with the
capability of running it's own guests (CONFIG_KVM_BOOK3S_HV_POSSIBLE).

Fixes: 95a6432ce903 "KVM: PPC: Book3S HV: Streamlined guest entry/exit path on P9 for radix guests"

Signed-off-by: Suraj Jitindar Singh <sjitindarsingh at gmail.com>
 arch/powerpc/include/asm/pmc.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/pmc.h b/arch/powerpc/include/asm/pmc.h
index dc9a1ca70edf..c6bbe9778d3c 100644
--- a/arch/powerpc/include/asm/pmc.h
+++ b/arch/powerpc/include/asm/pmc.h
@@ -27,11 +27,10 @@ static inline void ppc_set_pmu_inuse(int inuse)
 		get_lppaca()->pmcregs_in_use = inuse;
-	} else {
+	}
-		get_paca()->pmcregs_in_use = inuse;
+	get_paca()->pmcregs_in_use = inuse;
-	}

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