linux-kernel - [PATCH RFC 04/39] KVM: x86/xen: setup pvclock updates

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Date:   Wed, 20 Feb 2019 20:15:34 +0000
From:   Joao Martins <joao.m.martins@...cle.com>
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Ankur Arora <ankur.a.arora@...cle.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Joao Martins <joao.m.martins@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Subject: [PATCH RFC 04/39] 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@...cle.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 1eda96304180..6eb2afaa2af2 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 4df223bd3cd7..b4bd1949656e 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 bb38edf383fe..827c9390da34 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);
-- 
2.11.0