diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 9497792c4ee5661b098c2b41d12d7fb9e8b75673..c8ab2f7309451e67e2175d64ef4e84011a7d6c8d 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6231,6 +6231,10 @@ requires a guest to interact with host userpace.
For arm64:
----------
+SMCCC exits can be enabled depending on the configuration of the SMCCC
+filter. See the Documentation/virt/kvm/devices/vm.rst
+``KVM_ARM_SMCCC_FILTER`` for more details.
+
``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.
diff --git a/Documentation/virt/kvm/devices/vm.rst b/Documentation/virt/kvm/devices/vm.rst
index 147efec626e5218825e36d7e4035e07e4892d86b..9d726e60ec472a6eb3fb0c9453932954e604e6fb 100644
--- a/Documentation/virt/kvm/devices/vm.rst
+++ b/Documentation/virt/kvm/devices/vm.rst
@@ -321,3 +321,82 @@ Allows userspace to query the status of migration mode.
if it is enabled
:Returns: -EFAULT if the given address is not accessible from kernel space;
0 in case of success.
+
+6. GROUP: KVM_ARM_VM_SMCCC_CTRL
+===============================
+
+:Architectures: arm64
+
+6.1. ATTRIBUTE: KVM_ARM_VM_SMCCC_FILTER (w/o)
+---------------------------------------------
+
+:Parameters: Pointer to a ``struct kvm_smccc_filter``
+
+:Returns:
+
+ ====== ===========================================
+ EEXIST Range intersects with a previously inserted
+ or reserved range
+ EBUSY A vCPU in the VM has already run
+ EINVAL Invalid filter configuration
+ ENOMEM Failed to allocate memory for the in-kernel
+ representation of the SMCCC filter
+ ====== ===========================================
+
+Requests the installation of an SMCCC call filter described as follows::
+
+ enum kvm_smccc_filter_action {
+ KVM_SMCCC_FILTER_HANDLE = 0,
+ KVM_SMCCC_FILTER_DENY,
+ KVM_SMCCC_FILTER_FWD_TO_USER,
+ };
+
+ struct kvm_smccc_filter {
+ __u32 base;
+ __u32 nr_functions;
+ __u8 action;
+ __u8 pad[15];
+ };
+
+The filter is defined as a set of non-overlapping ranges. Each
+range defines an action to be applied to SMCCC calls within the range.
+Userspace can insert multiple ranges into the filter by using
+successive calls to this attribute.
+
+The default configuration of KVM is such that all implemented SMCCC
+calls are allowed. Thus, the SMCCC filter can be defined sparsely
+by userspace, only describing ranges that modify the default behavior.
+
+The range expressed by ``struct kvm_smccc_filter`` is
+[``base``, ``base + nr_functions``). The range is not allowed to wrap,
+i.e. userspace cannot rely on ``base + nr_functions`` overflowing.
+
+The SMCCC filter applies to both SMC and HVC calls initiated by the
+guest. The SMCCC filter gates the in-kernel emulation of SMCCC calls
+and as such takes effect before other interfaces that interact with
+SMCCC calls (e.g. hypercall bitmap registers).
+
+Actions:
+
+ - ``KVM_SMCCC_FILTER_HANDLE``: Allows the guest SMCCC call to be
+ handled in-kernel. It is strongly recommended that userspace *not*
+ explicitly describe the allowed SMCCC call ranges.
+
+ - ``KVM_SMCCC_FILTER_DENY``: Rejects the guest SMCCC call in-kernel
+ and returns to the guest.
+
+ - ``KVM_SMCCC_FILTER_FWD_TO_USER``: The guest SMCCC call is forwarded
+ to userspace with an exit reason of ``KVM_EXIT_HYPERCALL``.
+
+The ``pad`` field is reserved for future use and must be zero. KVM may
+return ``-EINVAL`` if the field is nonzero.
+
+KVM reserves the 'Arm Architecture Calls' range of function IDs and
+will reject attempts to define a filter for any portion of these ranges:
+
+ =========== ===============
+ Start End (inclusive)
+ =========== ===============
+ 0x8000_0000 0x8000_FFFF
+ 0xC000_0000 0xC000_FFFF
+ =========== ===============
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index f86446c5a7e300695eb0aceadf6d2e8fa5dc44fa..3dcfa4bfdf83f275a266e6e8afa1678914ee5de9 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -372,6 +372,10 @@ enum {
#endif
};
+/* Device Control API on vm fd */
+#define KVM_ARM_VM_SMCCC_CTRL 0
+#define KVM_ARM_VM_SMCCC_FILTER 0
+
/* Device Control API: ARM VGIC */
#define KVM_DEV_ARM_VGIC_GRP_ADDR 0
#define KVM_DEV_ARM_VGIC_GRP_DIST_REGS 1
@@ -479,6 +483,13 @@ enum kvm_smccc_filter_action {
#endif
};
+struct kvm_smccc_filter {
+ __u32 base;
+ __u32 nr_functions;
+ __u8 action;
+ __u8 pad[15];
+};
+
/* arm64-specific KVM_EXIT_HYPERCALL flags */
#define KVM_HYPERCALL_EXIT_SMC (1U << 0)
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 1202ac03bee0717aff60dda8fcdc8570b143ddc2..efee032c95602fa843563e80d89561f45f67bc1d 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1444,6 +1444,8 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
static int kvm_vm_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
{
switch (attr->group) {
+ case KVM_ARM_VM_SMCCC_CTRL:
+ return kvm_vm_smccc_has_attr(kvm, attr);
default:
return -ENXIO;
}
@@ -1452,6 +1454,8 @@ static int kvm_vm_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
static int kvm_vm_set_attr(struct kvm *kvm, struct kvm_device_attr *attr)
{
switch (attr->group) {
+ case KVM_ARM_VM_SMCCC_CTRL:
+ return kvm_vm_smccc_set_attr(kvm, attr);
default:
return -ENXIO;
}
diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
index 2db53709bec15aa9cef8bbfa264849ee29a39ce3..9a35d6d18193edc71d12c0eb674349e714523834 100644
--- a/arch/arm64/kvm/hypercalls.c
+++ b/arch/arm64/kvm/hypercalls.c
@@ -145,6 +145,44 @@ static void init_smccc_filter(struct kvm *kvm)
WARN_ON_ONCE(r);
}
+static int kvm_smccc_set_filter(struct kvm *kvm, struct kvm_smccc_filter __user *uaddr)
+{
+ const void *zero_page = page_to_virt(ZERO_PAGE(0));
+ struct kvm_smccc_filter filter;
+ u32 start, end;
+ int r;
+
+ if (copy_from_user(&filter, uaddr, sizeof(filter)))
+ return -EFAULT;
+
+ if (memcmp(filter.pad, zero_page, sizeof(filter.pad)))
+ return -EINVAL;
+
+ start = filter.base;
+ end = start + filter.nr_functions - 1;
+
+ if (end < start || filter.action >= NR_SMCCC_FILTER_ACTIONS)
+ return -EINVAL;
+
+ mutex_lock(&kvm->lock);
+
+ if (kvm_vm_has_ran_once(kvm)) {
+ r = -EBUSY;
+ goto out_unlock;
+ }
+
+ r = mtree_insert_range(&kvm->arch.smccc_filter, start, end,
+ xa_mk_value(filter.action), GFP_KERNEL_ACCOUNT);
+ if (r)
+ goto out_unlock;
+
+ set_bit(KVM_ARCH_FLAG_SMCCC_FILTER_CONFIGURED, &kvm->arch.flags);
+
+out_unlock:
+ mutex_unlock(&kvm->lock);
+ return r;
+}
+
static u8 kvm_smccc_filter_get_action(struct kvm *kvm, u32 func_id)
{
unsigned long idx = func_id;
@@ -569,3 +607,25 @@ int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
return -EINVAL;
}
+
+int kvm_vm_smccc_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+ switch (attr->attr) {
+ case KVM_ARM_VM_SMCCC_FILTER:
+ return 0;
+ default:
+ return -ENXIO;
+ }
+}
+
+int kvm_vm_smccc_set_attr(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+ void __user *uaddr = (void __user *)attr->addr;
+
+ switch (attr->attr) {
+ case KVM_ARM_VM_SMCCC_FILTER:
+ return kvm_smccc_set_filter(kvm, uaddr);
+ default:
+ return -ENXIO;
+ }
+}
diff --git a/include/kvm/arm_hypercalls.h b/include/kvm/arm_hypercalls.h
index fe6c31575b05e7c738a9b088f8248549e645ea8b..2df152207ccd00bc8abb53f6b0827cfc4ee96e5c 100644
--- a/include/kvm/arm_hypercalls.h
+++ b/include/kvm/arm_hypercalls.h
@@ -49,4 +49,7 @@ int kvm_arm_copy_fw_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices);
int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
+int kvm_vm_smccc_has_attr(struct kvm *kvm, struct kvm_device_attr *attr);
+int kvm_vm_smccc_set_attr(struct kvm *kvm, struct kvm_device_attr *attr);
+
#endif