[09/15] KVM: x86/xen: setup pvclock updates

Commit Message

David Woodhouse Dec. 4, 2020, 1:18 a.m. UTC

From: Joao Martins <[e-mail]>

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 4KiB 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 <[e-mail]>
Signed-off-by: David Woodhouse <[e-mail]>
---
 arch/x86/kvm/x86.c |  2 ++
 arch/x86/kvm/xen.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++
 arch/x86/kvm/xen.h |  1 +
 3 files changed, 53 insertions(+)

Patch

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 156ce72ba9bf..daf4a1f26811 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2719,6 +2719,8 @@  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 c156ed1ef972..c0fd54f1c121 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -55,9 +55,59 @@  static int kvm_xen_shared_info_init(struct kvm *kvm, gfn_t gfn)
 	if (ret)
 		return ret;
 
+	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;
+
+	BUILD_BUG_ON(offsetof(struct pvclock_vcpu_time_info, version) != 0);
+	BUILD_BUG_ON(offsetof(struct shared_info, vcpu_info) != 0);
+	BUILD_BUG_ON(offsetof(struct compat_shared_info, vcpu_info) != 0);
+	BUILD_BUG_ON(sizeof(struct vcpu_info) != sizeof(struct compat_vcpu_info));
+	BUILD_BUG_ON(offsetof(struct vcpu_info, time) !=
+		     offsetof(struct compat_vcpu_info, time));
+
+	offset = v->vcpu_id * sizeof(struct vcpu_info);
+	offset += offsetof(struct vcpu_info, time);
+
+	guest_hv_clock = v->kvm->arch.xen.shinfo + offset;
+
+	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 870ac7197a3a..0b6bfe4ee108 100644
--- a/arch/x86/kvm/xen.h
+++ b/arch/x86/kvm/xen.h
@@ -9,6 +9,7 @@ 
 #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);
 int kvm_xen_hypercall(struct kvm_vcpu *vcpu);