On Tue, Nov 07, 2017 at 05:25:28PM +0100, Andrew Jones wrote:

On Thu, Oct 12, 2017 at 12:41:20PM +0200, Christoffer Dall wrote:

quoted

The VHE switch function calls __timer_enable_traps and
__timer_disable_traps which don't do anything on VHE systems.
Therefore, simply remove these calls from the VHE switch function and
make the functions non-conditional as they are now only called from the
non-VHE switch path.

Signed-off-by: Christoffer Dall <redacted>
---
 arch/arm64/kvm/hyp/switch.c |  2 --
 virt/kvm/arm/hyp/timer-sr.c | 10 ++--------
 2 files changed, 2 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index 2cedf12..b98b73b 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c

@@ -336,7 +336,6 @@ int kvm_vcpu_run(struct kvm_vcpu *vcpu)
 	__activate_vm(vcpu);
 
 	__vgic_restore_state(vcpu);
-	__timer_enable_traps(vcpu);
 
 	/*
 	 * We must restore the 32-bit state before the sysregs, thanks

@@ -356,7 +355,6 @@ int kvm_vcpu_run(struct kvm_vcpu *vcpu)
 
 	__sysreg_save_guest_state(guest_ctxt);
 	__sysreg32_save_state(vcpu);
-	__timer_disable_traps(vcpu);
 	__vgic_save_state(vcpu);
 
 	__deactivate_traps(vcpu);

diff --git a/virt/kvm/arm/hyp/timer-sr.c b/virt/kvm/arm/hyp/timer-sr.c
index f398616..82c217e 100644
--- a/virt/kvm/arm/hyp/timer-sr.c
+++ b/virt/kvm/arm/hyp/timer-sr.c

@@ -53,16 +53,10 @@ void __hyp_text disable_el1_phys_timer_access(void)
 
 void __hyp_text __timer_disable_traps(struct kvm_vcpu *vcpu)
 {
-	/*
-	 * We don't need to do this for VHE since the host kernel runs in EL2
-	 * with HCR_EL2.TGE ==1, which makes those bits have no impact.
-	 */

I was about to suggest that we should move this comment, instead of remove
it, but it seems misleading anyway. We do call
enable/disable_el1_phys_timer_access on VHE, but at VCPU load/put time
instead of VM enter/exit time. So I guess removing it is best.

That was actually a bug in the timer series, which has now been fixed.
In any case, I don't think the comment is necessary as it's already
explained in kvm_timer_init_vhe() in arch_timer.c.

quoted

-	if (!has_vhe())
-		enable_el1_phys_timer_access();
+	enable_el1_phys_timer_access();
 }
 
 void __hyp_text __timer_enable_traps(struct kvm_vcpu *vcpu)
 {
-	if (!has_vhe())
-		disable_el1_phys_timer_access();
+	disable_el1_phys_timer_access();
 }
-- 
2.9.0

Should we just call enable/disable_el1_phys_timer_access directly from
__kvm_vcpu_run for non-VHE and drop this extra function level?

I don't think there's a problem with this indirection and we could
imagine having more traps in the future.

Thanks,
-Christoffer