KVM: arm64: Check whether a VM IOCTL is allowed in pKVM

Certain VM IOCTLs are tied to specific VM features. Since pKVM does not
support all features, restrict which IOCTLs are allowed depending on
whether the associated feature is supported.

Use the existing VM capability check as the source of truth to whether
an IOCTL is allowed for a particular VM by mapping the IOCTLs with their
associated capabilities.

Suggested-by: Oliver Upton <oupton@kernel.org>
Signed-off-by: Fuad Tabba <tabba@google.com>
Link: https://patch.msgid.link/20251211104710.151771-9-tabba@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>

Author: Fuad Tabba

arch/arm64/include/asm/kvm_pkvm.h

@@ -9,6 +9,7 @@
 #include <linux/arm_ffa.h>
 #include <linux/memblock.h>
 #include <linux/scatterlist.h>
+#include <asm/kvm_host.h>
 #include <asm/kvm_pgtable.h>
 
 /* Maximum number of VMs that can co-exist under pKVM. */
@@ -51,6 +52,25 @@ static inline bool kvm_pkvm_ext_allowed(struct kvm *kvm, long ext)
 	}
 }
 
+/*
+ * Check whether the KVM VM IOCTL is allowed in pKVM.
+ *
+ * Certain features are allowed only for non-protected VMs in pKVM, which is why
+ * this takes the VM (kvm) as a parameter.
+ */
+static inline bool kvm_pkvm_ioctl_allowed(struct kvm *kvm, unsigned int ioctl)
+{
+	long ext;
+	int r;
+
+	r = kvm_get_cap_for_kvm_ioctl(ioctl, &ext);
+
+	if (WARN_ON_ONCE(r < 0))
+		return false;
+
+	return kvm_pkvm_ext_allowed(kvm, ext);
+}
+
 extern struct memblock_region kvm_nvhe_sym(hyp_memory)[];
 extern unsigned int kvm_nvhe_sym(hyp_memblock_nr);
 

arch/arm64/kvm/arm.c

@@ -1938,6 +1938,9 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
 	void __user *argp = (void __user *)arg;
 	struct kvm_device_attr attr;
 
+	if (is_protected_kvm_enabled() && !kvm_pkvm_ioctl_allowed(kvm, ioctl))
+		return -EINVAL;
+
 	switch (ioctl) {
 	case KVM_CREATE_IRQCHIP: {
 		int ret;