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-rw-r--r--Documentation/virt/kvm/api.rst18
-rw-r--r--arch/arm64/include/uapi/asm/kvm.h4
-rw-r--r--arch/arm64/kvm/handle_exit.c4
-rw-r--r--arch/arm64/kvm/hypercalls.c16
4 files changed, 39 insertions, 3 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 9b01e3d0e757..9497792c4ee5 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6221,11 +6221,25 @@ to the byte array.
__u64 flags;
} hypercall;
-Unused. This was once used for 'hypercall to userspace'. To implement
-such functionality, use KVM_EXIT_IO (x86) or KVM_EXIT_MMIO (all except s390).
+
+It is strongly recommended that userspace use ``KVM_EXIT_IO`` (x86) or
+``KVM_EXIT_MMIO`` (all except s390) to implement functionality that
+requires a guest to interact with host userpace.
.. note:: KVM_EXIT_IO is significantly faster than KVM_EXIT_MMIO.
+For arm64:
+----------
+
+``nr`` contains the function ID of the guest's SMCCC call. Userspace is
+expected to use the ``KVM_GET_ONE_REG`` ioctl to retrieve the call
+parameters from the vCPU's GPRs.
+
+Definition of ``flags``:
+ - ``KVM_HYPERCALL_EXIT_SMC``: Indicates that the guest used the SMC
+ conduit to initiate the SMCCC call. If this bit is 0 then the guest
+ used the HVC conduit for the SMCCC call.
+
::
/* KVM_EXIT_TPR_ACCESS */
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index f9672ef1159a..f86446c5a7e3 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -472,12 +472,16 @@ enum {
enum kvm_smccc_filter_action {
KVM_SMCCC_FILTER_HANDLE = 0,
KVM_SMCCC_FILTER_DENY,
+ KVM_SMCCC_FILTER_FWD_TO_USER,
#ifdef __KERNEL__
NR_SMCCC_FILTER_ACTIONS
#endif
};
+/* arm64-specific KVM_EXIT_HYPERCALL flags */
+#define KVM_HYPERCALL_EXIT_SMC (1U << 0)
+
#endif
#endif /* __ARM_KVM_H__ */
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 68f95dcd41a1..3f43e20c48b6 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -71,7 +71,9 @@ static int handle_smc(struct kvm_vcpu *vcpu)
* Trap exception, not a Secure Monitor Call exception [...]"
*
* We need to advance the PC after the trap, as it would
- * otherwise return to the same address...
+ * otherwise return to the same address. Furthermore, pre-incrementing
+ * the PC before potentially exiting to userspace maintains the same
+ * abstraction for both SMCs and HVCs.
*/
kvm_incr_pc(vcpu);
diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
index ba7cd84c6668..2db53709bec1 100644
--- a/arch/arm64/kvm/hypercalls.c
+++ b/arch/arm64/kvm/hypercalls.c
@@ -180,6 +180,19 @@ static u8 kvm_smccc_get_action(struct kvm_vcpu *vcpu, u32 func_id)
return KVM_SMCCC_FILTER_DENY;
}
+static void kvm_prepare_hypercall_exit(struct kvm_vcpu *vcpu, u32 func_id)
+{
+ u8 ec = ESR_ELx_EC(kvm_vcpu_get_esr(vcpu));
+ struct kvm_run *run = vcpu->run;
+
+ run->exit_reason = KVM_EXIT_HYPERCALL;
+ run->hypercall.nr = func_id;
+ run->hypercall.flags = 0;
+
+ if (ec == ESR_ELx_EC_SMC32 || ec == ESR_ELx_EC_SMC64)
+ run->hypercall.flags |= KVM_HYPERCALL_EXIT_SMC;
+}
+
int kvm_smccc_call_handler(struct kvm_vcpu *vcpu)
{
struct kvm_smccc_features *smccc_feat = &vcpu->kvm->arch.smccc_feat;
@@ -195,6 +208,9 @@ int kvm_smccc_call_handler(struct kvm_vcpu *vcpu)
break;
case KVM_SMCCC_FILTER_DENY:
goto out;
+ case KVM_SMCCC_FILTER_FWD_TO_USER:
+ kvm_prepare_hypercall_exit(vcpu, func_id);
+ return 0;
default:
WARN_RATELIMIT(1, "Unhandled SMCCC filter action: %d\n", action);
goto out;