rt-patches/0295-KVM-arm-arm64-downgrade-preempt_disable-d-region-to-.patch

   1 From 0af37f87ac7df6ccdae98ea45514f626d3e72589 Mon Sep 17 00:00:00 2001
   2 From: Josh Cartwright <joshc@ni.com>
   3 Date: Thu, 11 Feb 2016 11:54:01 -0600
   4 Subject: [PATCH 295/366] KVM: arm/arm64: downgrade preempt_disable()d region
   5  to migrate_disable()
   6
   7 kvm_arch_vcpu_ioctl_run() disables the use of preemption when updating
   8 the vgic and timer states to prevent the calling task from migrating to
   9 another CPU.  It does so to prevent the task from writing to the
  10 incorrect per-CPU GIC distributor registers.
  11
  12 On -rt kernels, it's possible to maintain the same guarantee with the
  13 use of migrate_{disable,enable}(), with the added benefit that the
  14 migrate-disabled region is preemptible.  Update
  15 kvm_arch_vcpu_ioctl_run() to do so.
  16
  17 Cc: Christoffer Dall <christoffer.dall@linaro.org>
  18 Reported-by: Manish Jaggi <Manish.Jaggi@caviumnetworks.com>
  19 Signed-off-by: Josh Cartwright <joshc@ni.com>
  20 Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
  21 ---
  22  arch/arm/kvm/arm.c | 6 +++---
  23  1 file changed, 3 insertions(+), 3 deletions(-)
  24
  25 diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
  26 index 0310e51..64037a6 100644
  27 --- a/arch/arm/kvm/arm.c
  28 +++ b/arch/arm/kvm/arm.c
  29 @@ -566,7 +566,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
  30                  * involves poking the GIC, which must be done in a
  31                  * non-preemptible context.
  32                  */
  33 -               preempt_disable();
  34 +               migrate_disable();
  35                 kvm_timer_flush_hwstate(vcpu);
  36                 kvm_vgic_flush_hwstate(vcpu);
  37
  38 @@ -585,7 +585,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
  39                         local_irq_enable();
  40                         kvm_timer_sync_hwstate(vcpu);
  41                         kvm_vgic_sync_hwstate(vcpu);
  42 -                       preempt_enable();
  43 +                       migrate_enable();
  44                         continue;
  45                 }
  46
  47 @@ -639,7 +639,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
  48
  49                 kvm_vgic_sync_hwstate(vcpu);
  50
  51 -               preempt_enable();
  52 +               migrate_enable();
  53
  54                 ret = handle_exit(vcpu, run, ret);
  55         }
  56 --
  57 1.9.1
  58