[01/10] arm/arm64: KVM: Fix ordering of timer/GIC on guest entry
diff mbox

Message ID 1433783045-8002-2-git-send-email-marc.zyngier@arm.com
State New
Headers show

Commit Message

Marc Zyngier June 8, 2015, 5:03 p.m. UTC
As we now inject the timer interrupt when we're about to enter
the guest, it makes a lot more sense to make sure this happens
before the vgic code queues the pending interrupts.

Otherwise, we get the interrupt on the following exit, which is
not great for latency (and leads to all kind of bizarre issues
when using with active interrupts at the HW level).

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
 arch/arm/kvm/arm.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

Comments

Alex Bennée June 9, 2015, 11:29 a.m. UTC | #1
Marc Zyngier <marc.zyngier@arm.com> writes:

> As we now inject the timer interrupt when we're about to enter
> the guest, it makes a lot more sense to make sure this happens
> before the vgic code queues the pending interrupts.
>
> Otherwise, we get the interrupt on the following exit, which is
> not great for latency (and leads to all kind of bizarre issues
> when using with active interrupts at the HW level).
>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
>  arch/arm/kvm/arm.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index d9631ec..46db690 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -529,9 +529,10 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  		if (vcpu->arch.pause)
>  			vcpu_pause(vcpu);
>  
> -		kvm_vgic_flush_hwstate(vcpu);
>  		kvm_timer_flush_hwstate(vcpu);
>  
> +		kvm_vgic_flush_hwstate(vcpu);
> +
>  		local_irq_disable();
>  
>  		/*
> @@ -544,8 +545,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  
>  		if (ret <= 0 || need_new_vmid_gen(vcpu->kvm)) {
>  			local_irq_enable();
> -			kvm_timer_sync_hwstate(vcpu);
>  			kvm_vgic_sync_hwstate(vcpu);
> +			kvm_timer_sync_hwstate(vcpu);
>  			continue;
>  		}
>  
> @@ -577,9 +578,10 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  		 * Back from guest
>  		 *************************************************************/
>  
> -		kvm_timer_sync_hwstate(vcpu);
>  		kvm_vgic_sync_hwstate(vcpu);
>  
> +		kvm_timer_sync_hwstate(vcpu);
> +
>  		ret = handle_exit(vcpu, run, ret);
>  	}

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Christoffer Dall June 30, 2015, 8:19 p.m. UTC | #2
On Mon, Jun 08, 2015 at 06:03:56PM +0100, Marc Zyngier wrote:
> As we now inject the timer interrupt when we're about to enter
> the guest, it makes a lot more sense to make sure this happens
> before the vgic code queues the pending interrupts.
> 
> Otherwise, we get the interrupt on the following exit, which is
> not great for latency (and leads to all kind of bizarre issues
> when using with active interrupts at the HW level).
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
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Patch
diff mbox

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index d9631ec..46db690 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -529,9 +529,10 @@  int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
 		if (vcpu->arch.pause)
 			vcpu_pause(vcpu);
 
-		kvm_vgic_flush_hwstate(vcpu);
 		kvm_timer_flush_hwstate(vcpu);
 
+		kvm_vgic_flush_hwstate(vcpu);
+
 		local_irq_disable();
 
 		/*
@@ -544,8 +545,8 @@  int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
 
 		if (ret <= 0 || need_new_vmid_gen(vcpu->kvm)) {
 			local_irq_enable();
-			kvm_timer_sync_hwstate(vcpu);
 			kvm_vgic_sync_hwstate(vcpu);
+			kvm_timer_sync_hwstate(vcpu);
 			continue;
 		}
 
@@ -577,9 +578,10 @@  int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
 		 * Back from guest
 		 *************************************************************/
 
-		kvm_timer_sync_hwstate(vcpu);
 		kvm_vgic_sync_hwstate(vcpu);
 
+		kvm_timer_sync_hwstate(vcpu);
+
 		ret = handle_exit(vcpu, run, ret);
 	}