patches/KVM-arm-arm64-downgrade-preempt_disable-d-region-to-.patch

From 97ab74646324465d04881aa841a0d4352590b30a Mon Sep 17 00:00:00 2001
From: Josh Cartwright <joshc@ni.com>
Date: Thu, 11 Feb 2016 11:54:01 -0600
Subject: [PATCH] KVM: arm/arm64: downgrade preempt_disable()d region to
 migrate_disable()

kvm_arch_vcpu_ioctl_run() disables the use of preemption when updating
the vgic and timer states to prevent the calling task from migrating to
another CPU.  It does so to prevent the task from writing to the
incorrect per-CPU GIC distributor registers.

On -rt kernels, it's possible to maintain the same guarantee with the
use of migrate_{disable,enable}(), with the added benefit that the
migrate-disabled region is preemptible.  Update
kvm_arch_vcpu_ioctl_run() to do so.

Cc: Christoffer Dall <christoffer.dall@linaro.org>
Reported-by: Manish Jaggi <Manish.Jaggi@caviumnetworks.com>
Signed-off-by: Josh Cartwright <joshc@ni.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 3417e184c8e1..7d569ec59c46 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -628,7 +628,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
 		 * involves poking the GIC, which must be done in a
 		 * non-preemptible context.
 		 */
-		preempt_disable();
+		migrate_disable();
 
 		kvm_pmu_flush_hwstate(vcpu);
 
@@ -656,7 +656,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
 			kvm_pmu_sync_hwstate(vcpu);
 			kvm_timer_sync_hwstate(vcpu);
 			kvm_vgic_sync_hwstate(vcpu);
-			preempt_enable();
+			migrate_enable();
 			continue;
 		}
 
@@ -712,7 +712,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
 
 		kvm_vgic_sync_hwstate(vcpu);
 
-		preempt_enable();
+		migrate_enable();
 
 		ret = handle_exit(vcpu, run, ret);
 	}
-- 
2.1.4