[PATCH v2 14/15] KVM: arm64: nv: Add additional trap setup for CPTR_EL2

Oliver Upton
2024-06-13T20:18:57Z

From: Marc Zyngier <maz@kernel.org>

We need to teach KVM a couple of new tricks. CPTR_EL2 and its
VHE accessor CPACR_EL1 need to be handled specially:

- CPACR_EL1 is trapped on VHE so that we can track the TCPAC
and TTA bits

- CPTR_EL2.{TCPAC,E0POE} are propagated from L1 to L2

Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
arch/arm64/kvm/hyp/vhe/switch.c | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
index b0b1935a3626..d30fee61fb17 100644
--- a/arch/arm64/kvm/hyp/vhe/switch.c
+++ b/arch/arm64/kvm/hyp/vhe/switch.c
@@ -87,11 +87,23 @@ static void __activate_cptr_traps(struct kvm_vcpu *vcpu)
__activate_traps_fpsimd32(vcpu);
}

+ if (!vcpu_has_nv(vcpu))
+ goto write;
+
+ /*
+ * The architecture is a bit crap (what a surprise): an EL2 guest
+ * writing to CPTR_EL2 via CPACR_EL1 can't set any of TCPAC or TTA,
+ * as they are RES0 in the guest's view. To work around it, trap the
+ * sucker using the very same bit it can't set...
+ */
+ if (vcpu_el2_e2h_is_set(vcpu) && is_hyp_ctxt(vcpu))
+ val |= CPTR_EL2_TCPAC;
+
/*
* Layer the guest hypervisor's trap configuration on top of our own if
* we're in a nested context.
*/
- if (!vcpu_has_nv(vcpu) || is_hyp_ctxt(vcpu))
+ if (is_hyp_ctxt(vcpu))
goto write;

cptr = vcpu_sanitised_cptr_el2(vcpu);
@@ -115,6 +127,11 @@ static void __activate_cptr_traps(struct kvm_vcpu *vcpu)
if (!(SYS_FIELD_GET(CPACR_ELx, ZEN, cptr) & BIT(0)))
val &= ~CPACR_ELx_ZEN;

+ if (kvm_has_feat(vcpu->kvm, ID_AA64MMFR3_EL1, S2POE, IMP))
+ val |= cptr & CPACR_ELx_E0POE;
+
+ val |= cptr & CPTR_EL2_TCPAC;
+
write:
write_sysreg(val, cpacr_el1);
}
--
2.45.2.627.g7a2c4fd464-goog