From fe9b1fa63a6dfb136e1c4a5b690aecaaa4d0acdd Mon Sep 17 00:00:00 2001
From: Joao Martins <joao.m.martins@oracle.com>
Date: Fri, 1 Feb 2019 13:01:45 -0500
Subject: [PATCH] KVM: x86/xen: setup pvclock updates

This means when we set shared_info page GPA, and request a master
clock update. This will trigger all vcpus to update their respective
shared pvclock data with guests. We follow a similar approach
as Hyper-V and KVM and adjust it accordingly.

Note however that Xen differs a little on how pvclock pages are set up.
Specifically KVM assumes 4K page alignment and pvclock data starts in
the beginning of the page. Whereas Xen you can place that information
anywhere in the page.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
 arch/x86/kvm/x86.c |  2 ++
 arch/x86/kvm/xen.c | 47 ++++++++++++++++++++++++++++++++++++++++++++++
 arch/x86/kvm/xen.h |  1 +
 3 files changed, 50 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1eda963041803..6eb2afaa2af26 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2211,6 +2211,8 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
 
 	if (vcpu->pv_time_enabled)
 		kvm_setup_pvclock_page(v);
+	if (ka->xen.shinfo)
+		kvm_xen_setup_pvclock_page(v);
 	if (v == kvm_get_vcpu(v->kvm, 0))
 		kvm_hv_setup_tsc_page(v->kvm, &vcpu->hv_clock);
 	return 0;
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 4df223bd3cd7a..b4bd1949656eb 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -29,9 +29,56 @@ static int kvm_xen_shared_info_init(struct kvm *kvm, gfn_t gfn)
 	shared_info = page_to_virt(page);
 	memset(shared_info, 0, sizeof(struct shared_info));
 	kvm->arch.xen.shinfo = shared_info;
+
+	kvm_make_all_cpus_request(kvm, KVM_REQ_MASTERCLOCK_UPDATE);
 	return 0;
 }
 
+void kvm_xen_setup_pvclock_page(struct kvm_vcpu *v)
+{
+	struct kvm_vcpu_arch *vcpu = &v->arch;
+	struct pvclock_vcpu_time_info *guest_hv_clock;
+	unsigned int offset;
+
+	if (v->vcpu_id >= MAX_VIRT_CPUS)
+		return;
+
+	offset = offsetof(struct vcpu_info, time);
+	offset += offsetof(struct shared_info, vcpu_info);
+	offset += v->vcpu_id * sizeof(struct vcpu_info);
+
+	guest_hv_clock = (struct pvclock_vcpu_time_info *)
+		(((void *)v->kvm->arch.xen.shinfo) + offset);
+
+	BUILD_BUG_ON(offsetof(struct pvclock_vcpu_time_info, version) != 0);
+
+	if (guest_hv_clock->version & 1)
+		++guest_hv_clock->version;  /* first time write, random junk */
+
+	vcpu->hv_clock.version = guest_hv_clock->version + 1;
+	guest_hv_clock->version = vcpu->hv_clock.version;
+
+	smp_wmb();
+
+	/* retain PVCLOCK_GUEST_STOPPED if set in guest copy */
+	vcpu->hv_clock.flags |= (guest_hv_clock->flags & PVCLOCK_GUEST_STOPPED);
+
+	if (vcpu->pvclock_set_guest_stopped_request) {
+		vcpu->hv_clock.flags |= PVCLOCK_GUEST_STOPPED;
+		vcpu->pvclock_set_guest_stopped_request = false;
+	}
+
+	trace_kvm_pvclock_update(v->vcpu_id, &vcpu->hv_clock);
+
+	*guest_hv_clock = vcpu->hv_clock;
+
+	smp_wmb();
+
+	vcpu->hv_clock.version++;
+
+	guest_hv_clock->version = vcpu->hv_clock.version;
+}
+
 int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
 {
 	int r = -ENOENT;
diff --git a/arch/x86/kvm/xen.h b/arch/x86/kvm/xen.h
index bb38edf383fe5..827c9390da34a 100644
--- a/arch/x86/kvm/xen.h
+++ b/arch/x86/kvm/xen.h
@@ -3,6 +3,7 @@
 #ifndef __ARCH_X86_KVM_XEN_H__
 #define __ARCH_X86_KVM_XEN_H__
 
+void kvm_xen_setup_pvclock_page(struct kvm_vcpu *vcpu);
 int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data);
 int kvm_xen_hvm_get_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data);
 bool kvm_xen_hypercall_enabled(struct kvm *kvm);
-- 
2.50.1