linux-kernel - [PATCH 5.2 200/215] powerpc/pmu: Set pmcregs_in

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Date:   Mon, 29 Jul 2019 21:23:16 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Suraj Jitindar Singh <sjitindarsingh@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 5.2 200/215] powerpc/pmu: Set pmcregs_in_use in paca when running as LPAR

From: Suraj Jitindar Singh <sjitindarsingh@...il.com>

commit 28d2a6e6684d9851905f379816d8a4d03587ed94 upstream.

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")
Cc: stable@...r.kernel.org # v4.20+
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@...il.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://lore.kernel.org/r/20190703012022.15644-2-sjitindarsingh@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/include/asm/pmc.h |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- 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
 #ifdef CONFIG_PPC_PSERIES
 		get_lppaca()->pmcregs_in_use = inuse;
 #endif
-	} else {
+	}
 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
-		get_paca()->pmcregs_in_use = inuse;
+	get_paca()->pmcregs_in_use = inuse;
 #endif
-	}
 #endif
 }