[PATCH v2 04/15] KVM: arm64: nv: Load guest FP state for ZCR_EL2 trap

Oliver Upton
2024-06-13T20:18:38Z

Round out the ZCR_EL2 gymnastics by loading SVE state in the fast path
when the guest hypervisor tries to access SVE state.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
arch/arm64/kvm/hyp/include/hyp/switch.h | 4 ++++
arch/arm64/kvm/hyp/vhe/switch.c | 27 +++++++++++++++++++++++++
2 files changed, 31 insertions(+)

diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 428ee15dd6ae..5ecd2600d9df 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -345,6 +345,10 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)
if (guest_hyp_fpsimd_traps_enabled(vcpu))
return false;
break;
+ case ESR_ELx_EC_SYS64:
+ if (WARN_ON_ONCE(!is_hyp_ctxt(vcpu)))
+ return false;
+ fallthrough;
case ESR_ELx_EC_SVE:
if (!sve_guest)
return false;
diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
index fed36457fef9..f6e5ecd8b310 100644
--- a/arch/arm64/kvm/hyp/vhe/switch.c
+++ b/arch/arm64/kvm/hyp/vhe/switch.c
@@ -284,11 +284,38 @@ static bool kvm_hyp_handle_cpacr_el1(struct kvm_vcpu *vcpu, u64 *exit_code)
return true;
}

+static bool kvm_hyp_handle_zcr_el2(struct kvm_vcpu *vcpu, u64 *exit_code)
+{
+ u32 sysreg = esr_sys64_to_sysreg(kvm_vcpu_get_esr(vcpu));
+
+ if (!vcpu_has_nv(vcpu))
+ return false;
+
+ if (sysreg != SYS_ZCR_EL2)
+ return false;
+
+ if (guest_owns_fp_regs())
+ return false;
+
+ /*
+ * ZCR_EL2 traps are handled in the slow path, with the expectation
+ * that the guest's FP context has already been loaded onto the CPU.
+ *
+ * Load the guest's FP context and unconditionally forward to the
+ * slow path for handling (i.e. return false).
+ */
+ kvm_hyp_handle_fpsimd(vcpu, exit_code);
+ return false;
+}
+
static bool kvm_hyp_handle_sysreg_vhe(struct kvm_vcpu *vcpu, u64 *exit_code)
{
if (kvm_hyp_handle_cpacr_el1(vcpu, exit_code))
return true;

+ if (kvm_hyp_handle_zcr_el2(vcpu, exit_code))
+ return true;
+
return kvm_hyp_handle_sysreg(vcpu, exit_code);
}

--
2.45.2.627.g7a2c4fd464-goog