From e8138ca7346247f8e42a49f69b1670453c8820a1 Mon Sep 17 00:00:00 2001
From: Josh Cartwright <joshc@ni.com>
Date: Thu, 11 Feb 2016 11:54:01 -0600
Subject: [PATCH 143/158] 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>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/arm64/kvm/arm.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
Index: linux-5.15.19-rt29/arch/arm64/kvm/arm.c
===================================================================
@ linux-5.15.19-rt29/arch/arm64/kvm/arm.c:814 @ 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();
kvm_pmu_flush_hwstate(vcpu);
@ linux-5.15.19-rt29/arch/arm64/kvm/arm.c:838 @ int kvm_arch_vcpu_ioctl_run(struct kvm_v
kvm_timer_sync_user(vcpu);
kvm_vgic_sync_hwstate(vcpu);
local_irq_enable();
- preempt_enable();
+ migrate_enable();
continue;
}
@ linux-5.15.19-rt29/arch/arm64/kvm/arm.c:910 @ int kvm_arch_vcpu_ioctl_run(struct kvm_v
/* Exit types that need handling before we can be preempted */
handle_exit_early(vcpu, ret);
- preempt_enable();
+ migrate_enable();
/*
* The ARMv8 architecture doesn't give the hypervisor