@@ -16,6 +16,7 @@
#include <linux/types.h>
#include <linux/jump_label.h>
#include <linux/kvm_types.h>
+#include <linux/maple_tree.h>
#include <linux/percpu.h>
#include <linux/psci.h>
#include <asm/arch_gicv3.h>
@@ -213,7 +214,8 @@ struct kvm_arch {
#define KVM_ARCH_FLAG_EL1_32BIT 4
/* PSCI SYSTEM_SUSPEND enabled for the guest */
#define KVM_ARCH_FLAG_SYSTEM_SUSPEND_ENABLED 5
-
+ /* SMCCC filter initialized for the VM */
+#define KVM_ARCH_FLAG_SMCCC_FILTER_CONFIGURED 6
unsigned long flags;
/*
@@ -234,6 +236,7 @@ struct kvm_arch {
/* Hypercall features firmware registers' descriptor */
struct kvm_smccc_features smccc_feat;
+ struct maple_tree smccc_filter;
/*
* For an untrusted host VM, 'pkvm.handle' is used to lookup
@@ -202,6 +202,8 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
kvm_destroy_vcpus(kvm);
kvm_unshare_hyp(kvm, kvm + 1);
+
+ kvm_arm_teardown_hypercalls(kvm);
}
int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
@@ -121,8 +121,39 @@ static bool kvm_smccc_test_fw_bmap(struct kvm_vcpu *vcpu, u32 func_id)
}
}
+static bool kvm_smccc_filter_configured(struct kvm *kvm)
+{
+ return test_bit(KVM_ARCH_FLAG_SMCCC_FILTER_CONFIGURED, &kvm->arch.flags);
+}
+
+static u8 kvm_smccc_filter_get_action(struct kvm *kvm, u32 func_id)
+{
+ unsigned long index = func_id;
+ void *val;
+
+ if (!kvm_smccc_filter_configured(kvm))
+ return KVM_SMCCC_FILTER_ALLOW;
+
+ /*
+ * But where's the error handling, you say?
+ *
+ * mt_find() returns NULL if no entry was found, which just so happens
+ * to match KVM_SMCCC_FILTER_ALLOW.
+ */
+ val = mt_find(&kvm->arch.smccc_filter, &index, index);
+ return xa_to_value(val);
+}
+
static u8 kvm_hvc_get_action(struct kvm_vcpu *vcpu, u32 func_id)
{
+ /*
+ * Intervening actions in the SMCCC filter take precedence over the
+ * pseudo-firmware register bitmaps.
+ */
+ u8 action = kvm_smccc_filter_get_action(vcpu->kvm, func_id);
+ if (action != KVM_SMCCC_FILTER_ALLOW)
+ return action;
+
if (kvm_smccc_default_call(func_id) ||
kvm_smccc_test_fw_bmap(vcpu, func_id))
return KVM_SMCCC_FILTER_ALLOW;
@@ -256,6 +287,13 @@ void kvm_arm_init_hypercalls(struct kvm *kvm)
smccc_feat->std_bmap = KVM_ARM_SMCCC_STD_FEATURES;
smccc_feat->std_hyp_bmap = KVM_ARM_SMCCC_STD_HYP_FEATURES;
smccc_feat->vendor_hyp_bmap = KVM_ARM_SMCCC_VENDOR_HYP_FEATURES;
+
+ mt_init(&kvm->arch.smccc_filter);
+}
+
+void kvm_arm_teardown_hypercalls(struct kvm *kvm)
+{
+ mtree_destroy(&kvm->arch.smccc_filter);
}
int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu)
@@ -43,6 +43,7 @@ static inline void smccc_set_retval(struct kvm_vcpu *vcpu,
struct kvm_one_reg;
void kvm_arm_init_hypercalls(struct kvm *kvm);
+void kvm_arm_teardown_hypercalls(struct kvm *kvm);
int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu);
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);
Maple tree is an efficient B-tree implementation that is intended for storing non-overlapping intervals. Such a data structure is a good fit for the SMCCC filter as it is desirable to sparsely allocate the 32 bit function ID space. To that end, add a maple tree to kvm_arch and correctly init/teardown along with the VM. Wire in a test against the hypercall filter for HVCs which does nothing until the controls are exposed to userspace. Signed-off-by: Oliver Upton <oliver.upton@linux.dev> --- arch/arm64/include/asm/kvm_host.h | 5 +++- arch/arm64/kvm/arm.c | 2 ++ arch/arm64/kvm/hypercalls.c | 38 +++++++++++++++++++++++++++++++ include/kvm/arm_hypercalls.h | 1 + 4 files changed, 45 insertions(+), 1 deletion(-)