[PATCH v2 09/12] KVM: arm64: nv: Propagate CNTHCTL_EL2.EL1NV{P,V}CT bits

Marc Zyngier
2024-12-17T14:23:28Z

Allow a guest hypervisor to trap accesses to CNT{P,V}CT_EL02 by
propagating these trap bits to the host trap configuration.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/kvm/arch_timer.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
index 6f04f31c0a7f2..e5951e6eaf236 100644
--- a/arch/arm64/kvm/arch_timer.c
+++ b/arch/arm64/kvm/arch_timer.c
@@ -824,6 +824,10 @@ static void timer_set_traps(struct kvm_vcpu *vcpu, struct timer_map *map)
* Apply the enable bits that the guest hypervisor has requested for
* its own guest. We can only add traps that wouldn't have been set
* above.
+ * Implementation choices: we do not support NV when E2H=0 in the
+ * guest, and we don't support configuration where E2H is writable
+ * by the guest (either FEAT_VHE or FEAT_E2H0 is implemented, but
+ * not both). This simplifies the handling of the EL1NV* bits.
*/
if (vcpu_has_nv(vcpu) && !is_hyp_ctxt(vcpu)) {
u64 val = __vcpu_sys_reg(vcpu, CNTHCTL_EL2);
@@ -834,6 +838,9 @@ static void timer_set_traps(struct kvm_vcpu *vcpu, struct timer_map *map)

tpt |= !(val & (CNTHCTL_EL1PCEN << 10));
tpc |= !(val & (CNTHCTL_EL1PCTEN << 10));
+
+ tpt02 |= (val & CNTHCTL_EL1NVPCT);
+ tvt02 |= (val & CNTHCTL_EL1NVVCT);
}

/*
--
2.39.2