KVM: x86/xen: handle PV timers oneshot mode

If the guest has offloaded the timer virq, handle the following
hypercalls for programming the timer:

    VCPUOP_set_singleshot_timer
    VCPUOP_stop_singleshot_timer
    set_timer_op(timestamp_ns)

The event channel corresponding to the timer virq is then used to inject
events once timer deadlines are met. For now we back the PV timer with
hrtimer.

[ dwmw2: Add save/restore, 32-bit compat mode, immediate delivery,
         don't check timer in kvm_vcpu_has_event() ]

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220303154127.202856-13-dwmw2@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 9e34085..8193d52 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -614,6 +614,10 @@ struct kvm_vcpu_xen {
        u64 runstate_times[4];
        unsigned long evtchn_pending_sel;
        u32 vcpu_id; /* The Xen / ACPI vCPU ID */
+       u32 timer_virq;
+       u64 timer_expires; /* In guest epoch */
+       atomic_t timer_pending;
+       struct hrtimer timer;
 };
 
 struct kvm_vcpu_arch {

diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
index 172b053..f371f12 100644 (file)
--- a/arch/x86/kvm/irq.c
+++ b/arch/x86/kvm/irq.c
@@ -22,10 +22,14 @@
  */
 int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
 {
+       int r = 0;
+
        if (lapic_in_kernel(vcpu))
-               return apic_has_pending_timer(vcpu);
+               r = apic_has_pending_timer(vcpu);
+       if (kvm_xen_timer_enabled(vcpu))
+               r += kvm_xen_has_pending_timer(vcpu);
 
-       return 0;
+       return r;
 }
 EXPORT_SYMBOL(kvm_cpu_has_pending_timer);
 
@@ -143,6 +147,8 @@ void kvm_inject_pending_timer_irqs(struct kvm_vcpu *vcpu)
 {
        if (lapic_in_kernel(vcpu))
                kvm_inject_apic_timer_irqs(vcpu);
+       if (kvm_xen_timer_enabled(vcpu))
+               kvm_xen_inject_timer_irqs(vcpu);
 }
 EXPORT_SYMBOL_GPL(kvm_inject_pending_timer_irqs);
 

diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 244cf3c..0e1595d 100644 (file)
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -23,6 +23,7 @@
 
 #include "trace.h"
 
+static int kvm_xen_set_evtchn(struct kvm_xen_evtchn *xe, struct kvm *kvm);
 static int kvm_xen_setattr_evtchn(struct kvm *kvm, struct kvm_xen_hvm_attr *data);
 static bool kvm_xen_hcall_evtchn_send(struct kvm_vcpu *vcpu, u64 param, u64 *r);
 
@@ -108,6 +109,66 @@ out:
        return ret;
 }
 
+void kvm_xen_inject_timer_irqs(struct kvm_vcpu *vcpu)
+{
+       if (atomic_read(&vcpu->arch.xen.timer_pending) > 0) {
+               struct kvm_xen_evtchn e;
+
+               e.vcpu_id = vcpu->vcpu_id;
+               e.vcpu_idx = vcpu->vcpu_idx;
+               e.port = vcpu->arch.xen.timer_virq;
+               e.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
+
+               kvm_xen_set_evtchn(&e, vcpu->kvm);
+
+               vcpu->arch.xen.timer_expires = 0;
+               atomic_set(&vcpu->arch.xen.timer_pending, 0);
+       }
+}
+
+static enum hrtimer_restart xen_timer_callback(struct hrtimer *timer)
+{
+       struct kvm_vcpu *vcpu = container_of(timer, struct kvm_vcpu,
+                                            arch.xen.timer);
+       if (atomic_read(&vcpu->arch.xen.timer_pending))
+               return HRTIMER_NORESTART;
+
+       atomic_inc(&vcpu->arch.xen.timer_pending);
+       kvm_make_request(KVM_REQ_UNBLOCK, vcpu);
+       kvm_vcpu_kick(vcpu);
+
+       return HRTIMER_NORESTART;
+}
+
+static void kvm_xen_start_timer(struct kvm_vcpu *vcpu, u64 guest_abs, s64 delta_ns)
+{
+       atomic_set(&vcpu->arch.xen.timer_pending, 0);
+       vcpu->arch.xen.timer_expires = guest_abs;
+
+       if (delta_ns <= 0) {
+               xen_timer_callback(&vcpu->arch.xen.timer);
+       } else {
+               ktime_t ktime_now = ktime_get();
+               hrtimer_start(&vcpu->arch.xen.timer,
+                             ktime_add_ns(ktime_now, delta_ns),
+                             HRTIMER_MODE_ABS_HARD);
+       }
+}
+
+static void kvm_xen_stop_timer(struct kvm_vcpu *vcpu)
+{
+       hrtimer_cancel(&vcpu->arch.xen.timer);
+       vcpu->arch.xen.timer_expires = 0;
+       atomic_set(&vcpu->arch.xen.timer_pending, 0);
+}
+
+static void kvm_xen_init_timer(struct kvm_vcpu *vcpu)
+{
+       hrtimer_init(&vcpu->arch.xen.timer, CLOCK_MONOTONIC,
+                    HRTIMER_MODE_ABS_HARD);
+       vcpu->arch.xen.timer.function = xen_timer_callback;
+}
+
 static void kvm_xen_update_runstate(struct kvm_vcpu *v, int state)
 {
        struct kvm_vcpu_xen *vx = &v->arch.xen;
@@ -612,6 +673,28 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
                }
                break;
 
+       case KVM_XEN_VCPU_ATTR_TYPE_TIMER:
+               if (data->u.timer.port) {
+                       if (data->u.timer.priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL) {
+                               r = -EINVAL;
+                               break;
+                       }
+                       vcpu->arch.xen.timer_virq = data->u.timer.port;
+                       kvm_xen_init_timer(vcpu);
+
+                       /* Restart the timer if it's set */
+                       if (data->u.timer.expires_ns)
+                               kvm_xen_start_timer(vcpu, data->u.timer.expires_ns,
+                                                   data->u.timer.expires_ns -
+                                                   get_kvmclock_ns(vcpu->kvm));
+               } else if (kvm_xen_timer_enabled(vcpu)) {
+                       kvm_xen_stop_timer(vcpu);
+                       vcpu->arch.xen.timer_virq = 0;
+               }
+
+               r = 0;
+               break;
+
        default:
                break;
        }
@@ -692,6 +775,13 @@ int kvm_xen_vcpu_get_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
                r = 0;
                break;
 
+       case KVM_XEN_VCPU_ATTR_TYPE_TIMER:
+               data->u.timer.port = vcpu->arch.xen.timer_virq;
+               data->u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
+               data->u.timer.expires_ns = vcpu->arch.xen.timer_expires;
+               r = 0;
+               break;
+
        default:
                break;
        }
@@ -827,6 +917,112 @@ static bool kvm_xen_hcall_sched_op(struct kvm_vcpu *vcpu, int cmd, u64 param, u6
        return false;
 }
 
+struct compat_vcpu_set_singleshot_timer {
+    uint64_t timeout_abs_ns;
+    uint32_t flags;
+} __attribute__((packed));
+
+static bool kvm_xen_hcall_vcpu_op(struct kvm_vcpu *vcpu, bool longmode, int cmd,
+                                 int vcpu_id, u64 param, u64 *r)
+{
+       struct vcpu_set_singleshot_timer oneshot;
+       s64 delta;
+       gpa_t gpa;
+       int idx;
+
+       if (!kvm_xen_timer_enabled(vcpu))
+               return false;
+
+       switch (cmd) {
+       case VCPUOP_set_singleshot_timer:
+               if (vcpu->arch.xen.vcpu_id != vcpu_id) {
+                       *r = -EINVAL;
+                       return true;
+               }
+               idx = srcu_read_lock(&vcpu->kvm->srcu);
+               gpa = kvm_mmu_gva_to_gpa_system(vcpu, param, NULL);
+               srcu_read_unlock(&vcpu->kvm->srcu, idx);
+
+               /*
+                * The only difference for 32-bit compat is the 4 bytes of
+                * padding after the interesting part of the structure. So
+                * for a faithful emulation of Xen we have to *try* to copy
+                * the padding and return -EFAULT if we can't. Otherwise we
+                * might as well just have copied the 12-byte 32-bit struct.
+                */
+               BUILD_BUG_ON(offsetof(struct compat_vcpu_set_singleshot_timer, timeout_abs_ns) !=
+                            offsetof(struct vcpu_set_singleshot_timer, timeout_abs_ns));
+               BUILD_BUG_ON(sizeof_field(struct compat_vcpu_set_singleshot_timer, timeout_abs_ns) !=
+                            sizeof_field(struct vcpu_set_singleshot_timer, timeout_abs_ns));
+               BUILD_BUG_ON(offsetof(struct compat_vcpu_set_singleshot_timer, flags) !=
+                            offsetof(struct vcpu_set_singleshot_timer, flags));
+               BUILD_BUG_ON(sizeof_field(struct compat_vcpu_set_singleshot_timer, flags) !=
+                            sizeof_field(struct vcpu_set_singleshot_timer, flags));
+
+               if (!gpa ||
+                   kvm_vcpu_read_guest(vcpu, gpa, &oneshot, longmode ? sizeof(oneshot) :
+                                       sizeof(struct compat_vcpu_set_singleshot_timer))) {
+                       *r = -EFAULT;
+                       return true;
+               }
+
+               delta = oneshot.timeout_abs_ns - get_kvmclock_ns(vcpu->kvm);
+               if ((oneshot.flags & VCPU_SSHOTTMR_future) && delta < 0) {
+                       *r = -ETIME;
+                       return true;
+               }
+
+               kvm_xen_start_timer(vcpu, oneshot.timeout_abs_ns, delta);
+               *r = 0;
+               return true;
+
+       case VCPUOP_stop_singleshot_timer:
+               if (vcpu->arch.xen.vcpu_id != vcpu_id) {
+                       *r = -EINVAL;
+                       return true;
+               }
+               kvm_xen_stop_timer(vcpu);
+               *r = 0;
+               return true;
+       }
+
+       return false;
+}
+
+static bool kvm_xen_hcall_set_timer_op(struct kvm_vcpu *vcpu, uint64_t timeout,
+                                      u64 *r)
+{
+       if (!kvm_xen_timer_enabled(vcpu))
+               return false;
+
+       if (timeout) {
+               uint64_t guest_now = get_kvmclock_ns(vcpu->kvm);
+               int64_t delta = timeout - guest_now;
+
+               /* Xen has a 'Linux workaround' in do_set_timer_op() which
+                * checks for negative absolute timeout values (caused by
+                * integer overflow), and for values about 13 days in the
+                * future (2^50ns) which would be caused by jiffies
+                * overflow. For those cases, it sets the timeout 100ms in
+                * the future (not *too* soon, since if a guest really did
+                * set a long timeout on purpose we don't want to keep
+                * churning CPU time by waking it up).
+                */
+               if (unlikely((int64_t)timeout < 0 ||
+                            (delta > 0 && (uint32_t) (delta >> 50) != 0))) {
+                       delta = 100 * NSEC_PER_MSEC;
+                       timeout = guest_now + delta;
+               }
+
+               kvm_xen_start_timer(vcpu, timeout, delta);
+       } else {
+               kvm_xen_stop_timer(vcpu);
+       }
+
+       *r = 0;
+       return true;
+}
+
 int kvm_xen_hypercall(struct kvm_vcpu *vcpu)
 {
        bool longmode;
@@ -870,6 +1066,18 @@ int kvm_xen_hypercall(struct kvm_vcpu *vcpu)
        case __HYPERVISOR_sched_op:
                handled = kvm_xen_hcall_sched_op(vcpu, params[0], params[1], &r);
                break;
+       case __HYPERVISOR_vcpu_op:
+               handled = kvm_xen_hcall_vcpu_op(vcpu, longmode, params[0], params[1],
+                                               params[2], &r);
+               break;
+       case __HYPERVISOR_set_timer_op: {
+               u64 timeout = params[0];
+               /* In 32-bit mode, the 64-bit timeout is in two 32-bit params. */
+               if (!longmode)
+                       timeout |= params[1] << 32;
+               handled = kvm_xen_hcall_set_timer_op(vcpu, timeout, &r);
+               break;
+       }
        default:
                break;
        }
@@ -1398,6 +1606,9 @@ void kvm_xen_init_vcpu(struct kvm_vcpu *vcpu)
 
 void kvm_xen_destroy_vcpu(struct kvm_vcpu *vcpu)
 {
+       if (kvm_xen_timer_enabled(vcpu))
+               kvm_xen_stop_timer(vcpu);
+
        kvm_gfn_to_pfn_cache_destroy(vcpu->kvm,
                                     &vcpu->arch.xen.runstate_cache);
        kvm_gfn_to_pfn_cache_destroy(vcpu->kvm,

diff --git a/arch/x86/kvm/xen.h b/arch/x86/kvm/xen.h
index 54d587a..ee5c4ae 100644 (file)
--- a/arch/x86/kvm/xen.h
+++ b/arch/x86/kvm/xen.h
@@ -62,6 +62,20 @@ static inline bool kvm_xen_has_pending_events(struct kvm_vcpu *vcpu)
                vcpu->arch.xen.evtchn_pending_sel;
 }
 
+static inline bool kvm_xen_timer_enabled(struct kvm_vcpu *vcpu)
+{
+       return !!vcpu->arch.xen.timer_virq;
+}
+
+static inline int kvm_xen_has_pending_timer(struct kvm_vcpu *vcpu)
+{
+       if (kvm_xen_hypercall_enabled(vcpu->kvm) && kvm_xen_timer_enabled(vcpu))
+               return atomic_read(&vcpu->arch.xen.timer_pending);
+
+       return 0;
+}
+
+void kvm_xen_inject_timer_irqs(struct kvm_vcpu *vcpu);
 #else
 static inline int kvm_xen_write_hypercall_page(struct kvm_vcpu *vcpu, u64 data)
 {
@@ -107,6 +121,20 @@ static inline bool kvm_xen_has_pending_events(struct kvm_vcpu *vcpu)
 {
        return false;
 }
+
+static inline int kvm_xen_has_pending_timer(struct kvm_vcpu *vcpu)
+{
+       return 0;
+}
+
+static inline void kvm_xen_inject_timer_irqs(struct kvm_vcpu *vcpu)
+{
+}
+
+static inline bool kvm_xen_timer_enabled(struct kvm_vcpu *vcpu)
+{
+       return false;
+}
 #endif
 
 int kvm_xen_hypercall(struct kvm_vcpu *vcpu);

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 4b65e9f..cb223e4 100644 (file)
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1748,6 +1748,11 @@ struct kvm_xen_vcpu_attr {
                        __u64 time_offline;
                } runstate;
                __u32 vcpu_id;
+               struct {
+                       __u32 port;
+                       __u32 priority;
+                       __u64 expires_ns;
+               } timer;
        } u;
 };
 
@@ -1760,6 +1765,7 @@ struct kvm_xen_vcpu_attr {
 #define KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADJUST 0x5
 /* Available with KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_EVTCHN_SEND */
 #define KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID         0x6
+#define KVM_XEN_VCPU_ATTR_TYPE_TIMER           0x7
 
 /* Secure Encrypted Virtualization command */
 enum sev_cmd_id {