[PATCH RFC 07/39] KVM: x86/xen: register vcpu time info region

[Joao Martins]

Allow the Xen emulated guest the ability to register secondary
vcpu time information. On Xen guests this is used in order to be
mapped to userspace and hence allow vdso gettimeofday to work.

In doing so, move kvm_xen_set_pvclock_page() logic to
kvm_xen_update_vcpu_time() and have the former a top-level
function which updates primary vcpu time info (in struct vcpu_info)
and secondary one.

Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
---
 arch/x86/include/asm/kvm_host.h |  2 ++
 arch/x86/kvm/xen.c              | 45 ++++++++++++++++++++++++++++++-----------
 include/uapi/linux/kvm.h        |  1 +
 3 files changed, 36 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 96f65ba4b3c0..f39d50dd8f40 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -539,6 +539,8 @@ struct kvm_vcpu_xen {
 	struct kvm_xen_exit exit;
 	gpa_t vcpu_info_addr;
 	struct vcpu_info *vcpu_info;
+	gpa_t pv_time_addr;
+	struct pvclock_vcpu_time_info *pv_time;
 };
 
 struct kvm_vcpu_arch {
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 36d6dd0ea4b8..77d1153386bc 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -25,6 +25,11 @@ static void set_vcpu_attr(struct kvm_vcpu *v, u16 type, gpa_t gpa, void *addr)
 		vcpu_xen->vcpu_info = addr;
 		kvm_xen_setup_pvclock_page(v);
 		break;
+	case KVM_XEN_ATTR_TYPE_VCPU_TIME_INFO:
+		vcpu_xen->pv_time_addr = gpa;
+		vcpu_xen->pv_time = addr;
+		kvm_xen_setup_pvclock_page(v);
+		break;
 	default:
 		break;
 	}
@@ -37,6 +42,8 @@ static gpa_t get_vcpu_attr(struct kvm_vcpu *v, u16 type)
 	switch (type) {
 	case KVM_XEN_ATTR_TYPE_VCPU_INFO:
 		return vcpu_xen->vcpu_info_addr;
+	case KVM_XEN_ATTR_TYPE_VCPU_TIME_INFO:
+		return vcpu_xen->pv_time_addr;
 	default:
 		return 0;
 	}
@@ -83,20 +90,10 @@ static void *xen_vcpu_info(struct kvm_vcpu *v)
 	return hva + offset;
 }
 
-void kvm_xen_setup_pvclock_page(struct kvm_vcpu *v)
+static void kvm_xen_update_vcpu_time(struct kvm_vcpu *v,
+				 struct pvclock_vcpu_time_info *guest_hv_clock)
 {
 	struct kvm_vcpu_arch *vcpu = &v->arch;
-	struct pvclock_vcpu_time_info *guest_hv_clock;
-	void *hva = xen_vcpu_info(v);
-	unsigned int offset;
-
-	if (!hva)
-		return;
-
-	offset = offsetof(struct vcpu_info, time);
-
-	guest_hv_clock = (struct pvclock_vcpu_time_info *)
-		(hva + offset);
 
 	BUILD_BUG_ON(offsetof(struct pvclock_vcpu_time_info, version) != 0);
 
@@ -127,6 +124,26 @@ void kvm_xen_setup_pvclock_page(struct kvm_vcpu *v)
 	guest_hv_clock->version = vcpu->hv_clock.version;
 }
 
+void kvm_xen_setup_pvclock_page(struct kvm_vcpu *v)
+{
+	struct kvm_vcpu_xen *vcpu_xen = vcpu_to_xen_vcpu(v);
+	struct pvclock_vcpu_time_info *guest_hv_clock;
+	void *hva = xen_vcpu_info(v);
+	unsigned int offset;
+
+	offset = offsetof(struct vcpu_info, time);
+	guest_hv_clock = (struct pvclock_vcpu_time_info *) (hva + offset);
+
+	if (likely(hva))
+		kvm_xen_update_vcpu_time(v, guest_hv_clock);
+
+	/* Update secondary pvclock region if registered */
+	if (vcpu_xen->pv_time_addr) {
+		guest_hv_clock = vcpu_xen->pv_time;
+		kvm_xen_update_vcpu_time(v, guest_hv_clock);
+	}
+}
+
 int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
 {
 	int r = -ENOENT;
@@ -138,6 +155,7 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
 		r = kvm_xen_shared_info_init(kvm, gfn);
 		break;
 	}
+	case KVM_XEN_ATTR_TYPE_VCPU_TIME_INFO:
 	case KVM_XEN_ATTR_TYPE_VCPU_INFO: {
 		gpa_t gpa = data->u.vcpu_attr.gpa;
 		struct kvm_vcpu *v;
@@ -173,6 +191,7 @@ int kvm_xen_hvm_get_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
 		data->u.shared_info.gfn = kvm->arch.xen.shinfo_addr;
 		break;
 	}
+	case KVM_XEN_ATTR_TYPE_VCPU_TIME_INFO:
 	case KVM_XEN_ATTR_TYPE_VCPU_INFO: {
 		struct kvm_vcpu *v;
 
@@ -261,6 +280,8 @@ void kvm_xen_vcpu_uninit(struct kvm_vcpu *vcpu)
 
 	if (vcpu_xen->vcpu_info)
 		put_page(virt_to_page(vcpu_xen->vcpu_info));
+	if (vcpu_xen->pv_time)
+		put_page(virt_to_page(vcpu_xen->pv_time));
 }
 
 void kvm_xen_destroy_vm(struct kvm *kvm)
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 782f497a0fdd..8296c3a2434f 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1474,6 +1474,7 @@ struct kvm_xen_hvm_attr {
 
 #define KVM_XEN_ATTR_TYPE_SHARED_INFO       0x0
 #define KVM_XEN_ATTR_TYPE_VCPU_INFO         0x1
+#define KVM_XEN_ATTR_TYPE_VCPU_TIME_INFO    0x2
 
 /* Secure Encrypted Virtualization command */
 enum sev_cmd_id {
-- 
2.11.0