linux-kernel - [PATCH 3.12 04/63] ARM: KVM: Fix MPIDR computing to support virtual clusters

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Date:	Thu, 30 Apr 2015 14:11:33 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Marc Zyngier <marc.zyngier@....com>,
	Christoffer Dall <christoffer.dall@...aro.org>,
	Shannon Zhao <shannon.zhao@...aro.org>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 04/63] ARM: KVM: Fix MPIDR computing to support virtual clusters

From: Marc Zyngier <marc.zyngier@....com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 2d1d841bd44e24b58a3d3cc4fa793670aaa38fbf upstream.

In order to be able to support more than 4 A7 or A15 CPUs,
we need to fix the MPIDR computing to reflect the fact that
both A15 and A7 can only exist in clusters of at most 4 CPUs.

Fix the MPIDR computing to allow virtual clusters to be exposed
to the guest.

Signed-off-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Christoffer Dall <christoffer.dall@...aro.org>
Signed-off-by: Shannon Zhao <shannon.zhao@...aro.org>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 arch/arm/kvm/coproc_a15.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/arm/kvm/coproc_a15.c b/arch/arm/kvm/coproc_a15.c
index bbd4b888dbf3..8611c5c45d93 100644
--- a/arch/arm/kvm/coproc_a15.c
+++ b/arch/arm/kvm/coproc_a15.c
@@ -27,11 +27,13 @@
 static void reset_mpidr(struct kvm_vcpu *vcpu, const struct coproc_reg *r)
 {
 	/*
-	 * Compute guest MPIDR. No need to mess around with different clusters
-	 * but we read the 'U' bit from the underlying hardware directly.
+	 * Compute guest MPIDR. We build a virtual cluster out of the
+	 * vcpu_id, but we read the 'U' bit from the underlying
+	 * hardware directly.
 	 */
-	vcpu->arch.cp15[c0_MPIDR] = (read_cpuid_mpidr() & MPIDR_SMP_BITMASK)
-					| vcpu->vcpu_id;
+	vcpu->arch.cp15[c0_MPIDR] = ((read_cpuid_mpidr() & MPIDR_SMP_BITMASK) |
+				   ((vcpu->vcpu_id >> 2) << MPIDR_LEVEL_BITS) |
+				   (vcpu->vcpu_id & 3));
 }
 
 #include "coproc.h"
-- 
2.3.5

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