KVM: arm64: nv: Add SVC trap forwarding

HFGITR_EL2 allows the trap of SVC instructions to EL2. Allow these
traps to be forwarded. Take this opportunity to deny any 32bit activity
when NV is enabled.
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Jing Zhang <jingzhangos@google.com>
Link: https://lore.kernel.org/r/20230815183903.2735724-24-maz@kernel.org

arch/arm64/kvm/arm.c

@@ -36,6 +36,7 @@
 #include <asm/kvm_arm.h>
 #include <asm/kvm_asm.h>
 #include <asm/kvm_mmu.h>
+#include <asm/kvm_nested.h>
 #include <asm/kvm_pkvm.h>
 #include <asm/kvm_emulate.h>
 #include <asm/sections.h>
@@ -818,6 +819,9 @@ static bool vcpu_mode_is_bad_32bit(struct kvm_vcpu *vcpu)
 	if (likely(!vcpu_mode_is_32bit(vcpu)))
 		return false;
 
+	if (vcpu_has_nv(vcpu))
+		return true;
+
 	return !kvm_supports_32bit_el0();
 }
 

arch/arm64/kvm/handle_exit.c

@@ -226,6 +226,17 @@ static int kvm_handle_eret(struct kvm_vcpu *vcpu)
 	return 1;
 }
 
+static int handle_svc(struct kvm_vcpu *vcpu)
+{
+	/*
+	 * So far, SVC traps only for NV via HFGITR_EL2. A SVC from a
+	 * 32bit guest would be caught by vpcu_mode_is_bad_32bit(), so
+	 * we should only have to deal with a 64 bit exception.
+	 */
+	kvm_inject_nested_sync(vcpu, kvm_vcpu_get_esr(vcpu));
+	return 1;
+}
+
 static exit_handle_fn arm_exit_handlers[] = {
 	[0 ... ESR_ELx_EC_MAX]	= kvm_handle_unknown_ec,
 	[ESR_ELx_EC_WFx]	= kvm_handle_wfx,
@@ -239,6 +250,7 @@ static exit_handle_fn arm_exit_handlers[] = {
 	[ESR_ELx_EC_SMC32]	= handle_smc,
 	[ESR_ELx_EC_HVC64]	= handle_hvc,
 	[ESR_ELx_EC_SMC64]	= handle_smc,
+	[ESR_ELx_EC_SVC64]	= handle_svc,
 	[ESR_ELx_EC_SYS64]	= kvm_handle_sys_reg,
 	[ESR_ELx_EC_SVE]	= handle_sve,
 	[ESR_ELx_EC_ERET]	= kvm_handle_eret,