diff mbox series

[3/3] KVM: arm64: timer: Consolidate NV configuration of virtual timers

Message ID 20250128161721.3279927-4-maz@kernel.org (mailing list archive)
State New
Headers show
Series KVM/arm64: timer fixes for 6.14 | expand

Commit Message

Marc Zyngier Jan. 28, 2025, 4:17 p.m. UTC 
The way we configure the virtual timers with NV is rather odd:

- the EL1 virtual timer gets setup in kvm_timer_vcpu_reset(). Why not?

- the EL2 virtual timer gets setup at vcpu_load time, which is really
  bizarre, because this really should be a one-off.

The reason for the second point is that this setup is conditionned
on HCR_EL2.E2H, as it decides whether CNTVOFF_EL2 applies to the
EL2 virtual counter or not. And of course, this is not known at
the point where we reset the timer. Huh.

Solve this by introducing a NV-specific init for the timers,
matching what we do for the other subsystems, that gets called
once we know for sure that the configuration is final (on first
vcpu run, effectively).

This makes kvm_timer_vcpu_load_nested_switch() slightly simpler.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/arch_timer.c  | 48 ++++++++++++++++--------------------
 arch/arm64/kvm/arm.c         |  3 +++
 include/kvm/arm_arch_timer.h |  1 +
 3 files changed, 25 insertions(+), 27 deletions(-)

Comments

Oliver Upton Jan. 30, 2025, 9:41 p.m. UTC | #1 
> +void kvm_timer_vcpu_nv_init(struct kvm_vcpu *vcpu)
> +{
> +	/*
> +	 * A vcpu running at EL2 is in charge of the offset applied to
> +	 * the virtual timer, so use the physical VM offset, and point
> +	 * the vcpu offset to CNTVOFF_EL2.
> +	 *
> +	 * The virtual offset behaviour is "interesting", as it always
> +	 * applies when HCR_EL2.E2H==0, but only when accessed from EL1 when
> +	 * HCR_EL2.E2H==1. Apply it to the HV timer when E2H==0.
> +	 */

I'm definitely being pedantic, but all the talk of an HV timer when
E2H==0 isn't sitting well with me. Since a programmable E2H has gone
out the window there isn't such thing as an HV timer when E2H==0, as
FEAT_VHE isn't implemented for the VM.

And along those lines, accesses to CNTHV_*_EL2 registers should undef
when FEAT_VHE isn't implemented for the VM but I don't think we have any
enforcement of that.
diff mbox series

Patch

diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
index e59836e0260cf..43109277281a7 100644
--- a/arch/arm64/kvm/arch_timer.c
+++ b/arch/arm64/kvm/arch_timer.c
@@ -759,21 +759,6 @@  static void kvm_timer_vcpu_load_nested_switch(struct kvm_vcpu *vcpu,
 					    timer_irq(map->direct_ptimer),
 					    &arch_timer_irq_ops);
 		WARN_ON_ONCE(ret);
-
-		/*
-		 * The virtual offset behaviour is "interesting", as it
-		 * always applies when HCR_EL2.E2H==0, but only when
-		 * accessed from EL1 when HCR_EL2.E2H==1. So make sure we
-		 * track E2H when putting the HV timer in "direct" mode.
-		 */
-		if (map->direct_vtimer == vcpu_hvtimer(vcpu)) {
-			struct arch_timer_offset *offs = &map->direct_vtimer->offset;
-
-			if (vcpu_el2_e2h_is_set(vcpu))
-				offs->vcpu_offset = NULL;
-			else
-				offs->vcpu_offset = &__vcpu_sys_reg(vcpu, CNTVOFF_EL2);
-		}
 	}
 }
 
@@ -1045,18 +1030,6 @@  void kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu)
 	for (int i = 0; i < nr_timers(vcpu); i++)
 		timer_set_ctl(vcpu_get_timer(vcpu, i), 0);
 
-	/*
-	 * A vcpu running at EL2 is in charge of the offset applied to
-	 * the virtual timer, so use the physical VM offset, and point
-	 * the vcpu offset to CNTVOFF_EL2.
-	 */
-	if (vcpu_has_nv(vcpu)) {
-		struct arch_timer_offset *offs = &vcpu_vtimer(vcpu)->offset;
-
-		offs->vcpu_offset = &__vcpu_sys_reg(vcpu, CNTVOFF_EL2);
-		offs->vm_offset = &vcpu->kvm->arch.timer_data.poffset;
-	}
-
 	if (timer->enabled) {
 		for (int i = 0; i < nr_timers(vcpu); i++)
 			kvm_timer_update_irq(vcpu, false,
@@ -1102,6 +1075,27 @@  static void timer_context_init(struct kvm_vcpu *vcpu, int timerid)
 	}
 }
 
+void kvm_timer_vcpu_nv_init(struct kvm_vcpu *vcpu)
+{
+	/*
+	 * A vcpu running at EL2 is in charge of the offset applied to
+	 * the virtual timer, so use the physical VM offset, and point
+	 * the vcpu offset to CNTVOFF_EL2.
+	 *
+	 * The virtual offset behaviour is "interesting", as it always
+	 * applies when HCR_EL2.E2H==0, but only when accessed from EL1 when
+	 * HCR_EL2.E2H==1. Apply it to the HV timer when E2H==0.
+	 */
+	struct arch_timer_offset *offs = &vcpu_vtimer(vcpu)->offset;
+	u64 *voff = __ctxt_sys_reg(&vcpu->arch.ctxt, CNTVOFF_EL2);
+
+	offs->vcpu_offset = voff;
+	offs->vm_offset = &vcpu->kvm->arch.timer_data.poffset;
+
+	if (!vcpu_el2_e2h_is_set(vcpu))
+		vcpu_hvtimer(vcpu)->offset.vcpu_offset = voff;
+}
+
 void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu)
 {
 	struct arch_timer_cpu *timer = vcpu_timer(vcpu);
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 0725a0b50a3e9..deb74ab5775aa 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -815,6 +815,9 @@  int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
 	if (ret)
 		return ret;
 
+	if (vcpu_has_nv(vcpu))
+		kvm_timer_vcpu_nv_init(vcpu);
+
 	/*
 	 * This needs to happen after any restriction has been applied
 	 * to the feature set.
diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
index 681cf0c8b9df4..351813133aef6 100644
--- a/include/kvm/arm_arch_timer.h
+++ b/include/kvm/arm_arch_timer.h
@@ -98,6 +98,7 @@  int __init kvm_timer_hyp_init(bool has_gic);
 int kvm_timer_enable(struct kvm_vcpu *vcpu);
 void kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu);
 void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu);
+void kvm_timer_vcpu_nv_init(struct kvm_vcpu *vcpu);
 void kvm_timer_sync_nested(struct kvm_vcpu *vcpu);
 void kvm_timer_sync_user(struct kvm_vcpu *vcpu);
 bool kvm_timer_should_notify_user(struct kvm_vcpu *vcpu);