From: Josh Cartwright <joshc@ni.com>
Date: Thu, 11 Feb 2016 11:54:01 -0600
Subject: KVM: arm/arm64: downgrade preempt_disable()d region to
 migrate_disable()
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git
Git-commit: 287660ce8429a7d1e7bd9b707c3efb9667c8c0e8
Patch-mainline: Queued in subsystem maintainer repository
References: SLE Realtime Extension

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>
Signed-off-by: Mike Galbraith <mgalbraith@suse.de>
---
 virt/kvm/arm/arm.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -673,7 +673,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_v
 		 * involves poking the GIC, which must be done in a
 		 * non-preemptible context.
 		 */
-		preempt_disable();
+		migrate_disable();
 
 		/* Flush FP/SIMD state that can't survive guest entry/exit */
 		kvm_fpsimd_flush_cpu_state();
@@ -712,7 +712,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_v
 			kvm_timer_sync_hwstate(vcpu);
 			kvm_vgic_sync_hwstate(vcpu);
 			local_irq_enable();
-			preempt_enable();
+			migrate_enable();
 			continue;
 		}
 
@@ -785,7 +785,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_v
 		/* Exit types that need handling before we can be preempted */
 		handle_exit_early(vcpu, run, ret);
 
-		preempt_enable();
+		migrate_enable();
 
 		ret = handle_exit(vcpu, run, ret);
 	}