Re: [PATCH v3 17/41] KVM: arm64: Remove noop calls to timer save/restore from VHE switch

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Hi Christoffer,

Sorry for the late reply.

On 13/02/18 22:31, Christoffer Dall wrote:
On Fri, Feb 09, 2018 at 05:53:43PM +0000, Julien Grall wrote:
Hi Christoffer,

On 01/12/2018 12:07 PM, Christoffer Dall wrote:
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.

Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
---
  arch/arm64/kvm/hyp/switch.c |  2 --
  virt/kvm/arm/hyp/timer-sr.c | 44 ++++++++++++++++++++++----------------------
  2 files changed, 22 insertions(+), 24 deletions(-)

diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index 9aadef6966bf..6175fcb33ed2 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -354,7 +354,6 @@ int kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu)
  	__activate_vm(vcpu->kvm);
  	__vgic_restore_state(vcpu);
-	__timer_enable_traps(vcpu);
  	/*
  	 * We must restore the 32-bit state before the sysregs, thanks
@@ -373,7 +372,6 @@ int kvm_vcpu_run_vhe(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 f24404b3c8df..77754a62eb0c 100644
--- a/virt/kvm/arm/hyp/timer-sr.c
+++ b/virt/kvm/arm/hyp/timer-sr.c
@@ -27,34 +27,34 @@ void __hyp_text __kvm_timer_set_cntvoff(u32 cntvoff_low, u32 cntvoff_high)
  	write_sysreg(cntvoff, cntvoff_el2);
  }
+/*
+ * Should only be called on non-VHE systems.
+ * VHE systems use EL2 timers and configure EL1 timers in kvm_timer_init_vhe().
+ */
  void __hyp_text __timer_disable_traps(struct kvm_vcpu *vcpu)

Would it be worth to suffix the function with nvhe? So it would be clear
that it should not be called for VHE system?

Actually, I decided against this, because it's also called from the
32-bit code and it looks a little strange there, and it's not like we
have an equivalent _vhe version.

The main goal was to provide a naming that would prevent someone to use it in VHE case. This would have also been inline with other patches where you rename some helpers to nvhe/vhe even in arm32 code.

Anyway, I guess the reviewers will be careful enough to spot that :).

Cheers,

--
Julien Grall



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