KVM: arm64: Provide VCPU attributes for stolen time

Allow user space to inform the KVM host where in the physical memory
map the paravirtualized time structures should be located.

User space can set an attribute on the VCPU providing the IPA base
address of the stolen time structure for that VCPU. This must be
repeated for every VCPU in the VM.

The address is given in terms of the physical address visible to
the guest and must be 64 byte aligned. The guest will discover the
address via a hypercall.

Signed-off-by: Steven Price <steven.price@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>

1 files changed, 59 insertions, 0 deletions

diff --git a/virt/kvm/arm/pvtime.c b/virt/kvm/arm/pvtime.c
index b90b3a7bea85..1e0f4c284888 100644
--- a/virt/kvm/arm/pvtime.c
+++ b/virt/kvm/arm/pvtime.c
@@ -2,7 +2,9 @@
 // Copyright (C) 2019 Arm Ltd.
 
 #include <linux/arm-smccc.h>
+#include <linux/kvm_host.h>
 
+#include <asm/kvm_mmu.h>
 #include <asm/pvclock-abi.h>
 
 #include <kvm/arm_hypercalls.h>
@@ -70,3 +72,60 @@ gpa_t kvm_init_stolen_time(struct kvm_vcpu *vcpu)
 
 	return base;
 }
+
+int kvm_arm_pvtime_set_attr(struct kvm_vcpu *vcpu,
+			    struct kvm_device_attr *attr)
+{
+	u64 __user *user = (u64 __user *)attr->addr;
+	struct kvm *kvm = vcpu->kvm;
+	u64 ipa;
+	int ret = 0;
+	int idx;
+
+	if (attr->attr != KVM_ARM_VCPU_PVTIME_IPA)
+		return -ENXIO;
+
+	if (get_user(ipa, user))
+		return -EFAULT;
+	if (!IS_ALIGNED(ipa, 64))
+		return -EINVAL;
+	if (vcpu->arch.steal.base != GPA_INVALID)
+		return -EEXIST;
+
+	/* Check the address is in a valid memslot */
+	idx = srcu_read_lock(&kvm->srcu);
+	if (kvm_is_error_hva(gfn_to_hva(kvm, ipa >> PAGE_SHIFT)))
+		ret = -EINVAL;
+	srcu_read_unlock(&kvm->srcu, idx);
+
+	if (!ret)
+		vcpu->arch.steal.base = ipa;
+
+	return ret;
+}
+
+int kvm_arm_pvtime_get_attr(struct kvm_vcpu *vcpu,
+			    struct kvm_device_attr *attr)
+{
+	u64 __user *user = (u64 __user *)attr->addr;
+	u64 ipa;
+
+	if (attr->attr != KVM_ARM_VCPU_PVTIME_IPA)
+		return -ENXIO;
+
+	ipa = vcpu->arch.steal.base;
+
+	if (put_user(ipa, user))
+		return -EFAULT;
+	return 0;
+}
+
+int kvm_arm_pvtime_has_attr(struct kvm_vcpu *vcpu,
+			    struct kvm_device_attr *attr)
+{
+	switch (attr->attr) {
+	case KVM_ARM_VCPU_PVTIME_IPA:
+		return 0;
+	}
+	return -ENXIO;
+}