[PATCH 07/11] KVM: arm64: Handle counter access early in non-HYP context

Marc Zyngier
2024-12-02T17:22:19Z

We already deal with CNTPCT_EL0 accesses in non-HYP context.
Let's add CNTVCT_EL0 as a good measure.

This is also an opportunity to simplify things and make it
plain that this code is only for non-HYP context handling.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/kvm/hyp/include/hyp/switch.h | 34 +++++++++++++++----------
1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 30e572de28749..719479b42b329 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -506,7 +506,7 @@ static inline u64 compute_counter_value(struct arch_timer_context *ctxt)
return arch_timer_read_cntpct_el0() - timer_get_offset(ctxt);
}

-static bool kvm_hyp_handle_cntpct(struct kvm_vcpu *vcpu)
+static bool kvm_handle_cntxct(struct kvm_vcpu *vcpu)
{
struct arch_timer_context *ctxt;
u32 sysreg;
@@ -516,18 +516,19 @@ static bool kvm_hyp_handle_cntpct(struct kvm_vcpu *vcpu)
* We only get here for 64bit guests, 32bit guests will hit
* the long and winding road all the way to the standard
* handling. Yes, it sucks to be irrelevant.
+ *
+ * Also, we only deal with non-hypervisor context here (either
+ * an EL1 guest, or a non-HYP context of an EL2 guest).
*/
+ if (is_hyp_ctxt(vcpu))
+ return false;
+
sysreg = esr_sys64_to_sysreg(kvm_vcpu_get_esr(vcpu));

switch (sysreg) {
case SYS_CNTPCT_EL0:
case SYS_CNTPCTSS_EL0:
if (vcpu_has_nv(vcpu)) {
- if (is_hyp_ctxt(vcpu)) {
- ctxt = vcpu_hptimer(vcpu);
- break;
- }
-
/* Check for guest hypervisor trapping */
val = __vcpu_sys_reg(vcpu, CNTHCTL_EL2);
if (!vcpu_el2_e2h_is_set(vcpu))
@@ -539,16 +540,23 @@ static bool kvm_hyp_handle_cntpct(struct kvm_vcpu *vcpu)

ctxt = vcpu_ptimer(vcpu);
break;
+ case SYS_CNTVCT_EL0:
+ case SYS_CNTVCTSS_EL0:
+ if (vcpu_has_nv(vcpu)) {
+ /* Check for guest hypervisor trapping */
+ val = __vcpu_sys_reg(vcpu, CNTHCTL_EL2);
+
+ if (val & CNTHCTL_EL1TVCT)
+ return false;
+ }
+
+ ctxt = vcpu_vtimer(vcpu);
+ break;
default:
return false;
}

- val = arch_timer_read_cntpct_el0();
-
- if (ctxt->offset.vm_offset)
- val -= *kern_hyp_va(ctxt->offset.vm_offset);
- if (ctxt->offset.vcpu_offset)
- val -= *kern_hyp_va(ctxt->offset.vcpu_offset);
+ val = compute_counter_value(ctxt);

vcpu_set_reg(vcpu, kvm_vcpu_sys_get_rt(vcpu), val);
__kvm_skip_instr(vcpu);
@@ -593,7 +601,7 @@ static bool kvm_hyp_handle_sysreg(struct kvm_vcpu *vcpu, u64 *exit_code)
__vgic_v3_perform_cpuif_access(vcpu) == 1)
return true;

- if (kvm_hyp_handle_cntpct(vcpu))
+ if (kvm_handle_cntxct(vcpu))
return true;

return false;
--
2.39.2