[PATCH v3 10/11] x86/vpt: remove vPT timers per-vCPU lists

Roger Pau Monne posted 11 patches 1 month, 1 week ago

[PATCH v3 10/11] x86/vpt: remove vPT timers per-vCPU lists

Posted by Roger Pau Monne 1 month, 1 week ago
No longer add vPT timers to lists on specific vCPUs, since there's no
need anymore to check if timer interrupts have been injected on return
to HVM guest.

Such change allows to get rid of virtual timers vCPU migration, and
also cleanup some of the virtual timers fields that are no longer
required.

The model is also slightly different now in that timers are not
stopped when a vCPU is de-scheduled. Such timers will continue
running, and when triggered the function will try to inject the
corresponding interrupt to the guest (which might be different than
the currently running one). Note that the timer triggering when the
guest is no longer running can only happen once, as the timer callback
will not reset the interrupt to fire again. Such resetting if required
will be done by the EOI callback.

Since virtual timers are no longer added to per-VCPU lists when active
a new 'masked' field is added to the structure, to signal whether a
timer has it's interrupt source currently masked.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
Changes since v2:
 - Remove pt_{save/restore}_timer and instead use
   pt_{freeze/thaw}_time.
 - Remove the introduction of the 'masked' field, it's not needed.
 - Rework pt_active to use timer_is_active.

Changes since v1:
 - New in this version.
---
 xen/arch/x86/domain.c          |   4 +-
 xen/arch/x86/hvm/hvm.c         |   4 +-
 xen/arch/x86/hvm/vlapic.c      |   1 -
 xen/arch/x86/hvm/vpt.c         | 174 ++++-----------------------------
 xen/include/asm-x86/hvm/vcpu.h |   3 +-
 xen/include/asm-x86/hvm/vpt.h  |  12 +--
 6 files changed, 27 insertions(+), 171 deletions(-)

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index b2127298800..a711ff2814a 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -2014,8 +2014,8 @@ void context_switch(struct vcpu *prev, struct vcpu *next)
     vpmu_switch_from(prev);
     np2m_schedule(NP2M_SCHEDLE_OUT);
 
-    if ( is_hvm_domain(prevd) && !list_empty(&prev->arch.hvm.tm_list) )
-        pt_save_timer(prev);
+    if ( is_hvm_domain(prevd) )
+        pt_freeze_time(prev);
 
     local_irq_disable();
 
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 0279014e66e..3a72da67ef2 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -489,7 +489,6 @@ void hvm_set_info_guest(struct vcpu *v)
 void hvm_migrate_timers(struct vcpu *v)
 {
     rtc_migrate_timers(v);
-    pt_migrate(v);
 }
 
 void hvm_migrate_pirq(struct hvm_pirq_dpci *pirq_dpci, const struct vcpu *v)
@@ -544,7 +543,7 @@ void hvm_do_resume(struct vcpu *v)
 {
     check_wakeup_from_wait();
 
-    pt_restore_timer(v);
+    pt_thaw_time(v);
 
     if ( !vcpu_ioreq_handle_completion(v) )
         return;
@@ -1558,7 +1557,6 @@ int hvm_vcpu_initialise(struct vcpu *v)
     hvm_asid_flush_vcpu(v);
 
     spin_lock_init(&v->arch.hvm.tm_lock);
-    INIT_LIST_HEAD(&v->arch.hvm.tm_list);
 
     rc = hvm_vcpu_cacheattr_init(v); /* teardown: vcpu_cacheattr_destroy */
     if ( rc != 0 )
diff --git a/xen/arch/x86/hvm/vlapic.c b/xen/arch/x86/hvm/vlapic.c
index 63fa3780767..8091b6d8925 100644
--- a/xen/arch/x86/hvm/vlapic.c
+++ b/xen/arch/x86/hvm/vlapic.c
@@ -1339,7 +1339,6 @@ void vlapic_adjust_i8259_target(struct domain *d)
     if ( d->arch.hvm.i8259_target == v )
         return;
     d->arch.hvm.i8259_target = v;
-    pt_adjust_global_vcpu_target(v);
 }
 
 int vlapic_has_pending_irq(struct vcpu *v)
diff --git a/xen/arch/x86/hvm/vpt.c b/xen/arch/x86/hvm/vpt.c
index f951cd95bcf..84d49c1b25c 100644
--- a/xen/arch/x86/hvm/vpt.c
+++ b/xen/arch/x86/hvm/vpt.c
@@ -126,18 +126,6 @@ static int pt_irq_masked(struct periodic_time *pt)
     return 1;
 }
 
-static void pt_vcpu_lock(struct vcpu *v)
-{
-    read_lock(&v->domain->arch.hvm.pl_time->pt_migrate);
-    spin_lock(&v->arch.hvm.tm_lock);
-}
-
-static void pt_vcpu_unlock(struct vcpu *v)
-{
-    spin_unlock(&v->arch.hvm.tm_lock);
-    read_unlock(&v->domain->arch.hvm.pl_time->pt_migrate);
-}
-
 static void pt_lock(struct periodic_time *pt)
 {
     /*
@@ -151,7 +139,8 @@ static void pt_lock(struct periodic_time *pt)
 
 static void pt_unlock(struct periodic_time *pt)
 {
-    pt_vcpu_unlock(pt->vcpu);
+    spin_unlock(&pt->vcpu->arch.hvm.tm_lock);
+    read_unlock(&pt->vcpu->domain->arch.hvm.pl_time->pt_migrate);
 }
 
 static void pt_process_missed_ticks(struct periodic_time *pt)
@@ -166,14 +155,12 @@ static void pt_process_missed_ticks(struct periodic_time *pt)
         return;
 
     missed_ticks = missed_ticks / (s_time_t) pt->period + 1;
-    if ( mode_is(pt->vcpu->domain, no_missed_ticks_pending) )
-        pt->do_not_freeze = !pt->pending_intr_nr;
-    else
+    if ( !mode_is(pt->vcpu->domain, no_missed_ticks_pending) )
         pt->pending_intr_nr += missed_ticks;
     pt->scheduled += missed_ticks * pt->period;
 }
 
-static void pt_freeze_time(struct vcpu *v)
+void pt_freeze_time(struct vcpu *v)
 {
     if ( !mode_is(v->domain, delay_for_missed_ticks) )
         return;
@@ -181,7 +168,7 @@ static void pt_freeze_time(struct vcpu *v)
     v->arch.hvm.guest_time = hvm_get_guest_time(v);
 }
 
-static void pt_thaw_time(struct vcpu *v)
+void pt_thaw_time(struct vcpu *v)
 {
     if ( !mode_is(v->domain, delay_for_missed_ticks) )
         return;
@@ -193,52 +180,11 @@ static void pt_thaw_time(struct vcpu *v)
     v->arch.hvm.guest_time = 0;
 }
 
-void pt_save_timer(struct vcpu *v)
-{
-    struct list_head *head = &v->arch.hvm.tm_list;
-    struct periodic_time *pt;
-
-    if ( v->pause_flags & VPF_blocked )
-        return;
-
-    pt_vcpu_lock(v);
-
-    list_for_each_entry ( pt, head, list )
-        if ( !pt->do_not_freeze )
-            stop_timer(&pt->timer);
-
-    pt_freeze_time(v);
-
-    pt_vcpu_unlock(v);
-}
-
-void pt_restore_timer(struct vcpu *v)
-{
-    struct list_head *head = &v->arch.hvm.tm_list;
-    struct periodic_time *pt;
-
-    pt_vcpu_lock(v);
-
-    list_for_each_entry ( pt, head, list )
-        if ( pt->pending_intr_nr == 0 )
-            set_timer(&pt->timer, pt->scheduled);
-
-    pt_thaw_time(v);
-
-    pt_vcpu_unlock(v);
-}
-
 static void pt_irq_fired(struct vcpu *v, struct periodic_time *pt)
 {
-    pt->irq_issued = false;
-
     if ( pt->one_shot )
     {
-        if ( pt->on_list )
-            list_del(&pt->list);
-        pt->on_list = false;
         pt->pending_intr_nr = 0;
-
         return;
     }
 
@@ -252,7 +198,11 @@ static void pt_irq_fired(struct vcpu *v, struct periodic_time *pt)
         pt_process_missed_ticks(pt);
 
     if ( !pt->pending_intr_nr )
+    {
+        /* Make sure timer follows vCPU. */
+        migrate_timer(&pt->timer, current->processor);
         set_timer(&pt->timer, pt->scheduled);
+    }
 }
 
 static void pt_timer_fn(void *data)
@@ -268,21 +218,15 @@ static void pt_timer_fn(void *data)
     v = pt->vcpu;
     irq = pt->irq;
 
-    if ( inject_interrupt(pt) )
+    pt->scheduled += pt->period;
+
+    if ( !inject_interrupt(pt) )
+        pt->pending_intr_nr++;
+    else
     {
-        pt->scheduled += pt->period;
-        pt->do_not_freeze = 0;
         cb = pt->cb;
         cb_priv = pt->priv;
     }
-    else
-    {
-        /* Masked. */
-        if ( pt->on_list )
-            list_del(&pt->list);
-        pt->on_list = false;
-        pt->pending_intr_nr++;
-    }
 
     pt_unlock(pt);
 
@@ -304,22 +248,12 @@ static void eoi_callback(unsigned int unused, void *data)
     pt_lock(pt);
 
     pt_irq_fired(pt->vcpu, pt);
-    if ( pt->pending_intr_nr )
+    if ( pt->pending_intr_nr && inject_interrupt(pt) )
     {
-        if ( inject_interrupt(pt) )
-        {
-            pt->pending_intr_nr--;
-            cb = pt->cb;
-            cb_priv = pt->priv;
-            v = pt->vcpu;
-        }
-        else
-        {
-            /* Masked. */
-            if ( pt->on_list )
-                list_del(&pt->list);
-            pt->on_list = false;
-        }
+        pt->pending_intr_nr--;
+        cb = pt->cb;
+        cb_priv = pt->priv;
+        v = pt->vcpu;
     }
 
     pt_unlock(pt);
@@ -378,19 +312,6 @@ static bool inject_interrupt(struct periodic_time *pt)
     return true;
 }
 
-void pt_migrate(struct vcpu *v)
-{
-    struct list_head *head = &v->arch.hvm.tm_list;
-    struct periodic_time *pt;
-
-    pt_vcpu_lock(v);
-
-    list_for_each_entry ( pt, head, list )
-        migrate_timer(&pt->timer, v->processor);
-
-    pt_vcpu_unlock(v);
-}
-
 void create_periodic_time(
     struct vcpu *v, struct periodic_time *pt, uint64_t delta,
     uint64_t period, uint8_t irq, time_cb *cb, void *data, bool level)
@@ -410,8 +331,6 @@ void create_periodic_time(
     write_lock(&v->domain->arch.hvm.pl_time->pt_migrate);
 
     pt->pending_intr_nr = 0;
-    pt->do_not_freeze = 0;
-    pt->irq_issued = 0;
 
     /* Periodic timer must be at least 0.1ms. */
     if ( (period < 100000) && period )
@@ -469,9 +388,6 @@ void create_periodic_time(
         break;
     }
 
-    pt->on_list = 1;
-    list_add(&pt->list, &v->arch.hvm.tm_list);
-
     init_timer(&pt->timer, pt_timer_fn, pt, v->processor);
     set_timer(&pt->timer, pt->scheduled);
 
@@ -487,9 +403,6 @@ void destroy_periodic_time(struct periodic_time *pt)
         return;
 
     pt_lock(pt);
-    if ( pt->on_list )
-        list_del(&pt->list);
-    pt->on_list = 0;
     pt->pending_intr_nr = 0;
 
     gsi = pt->irq;
@@ -511,51 +424,6 @@ void destroy_periodic_time(struct periodic_time *pt)
     kill_timer(&pt->timer);
 }
 
-static void pt_adjust_vcpu(struct periodic_time *pt, struct vcpu *v)
-{
-    ASSERT(pt->source == PTSRC_isa || pt->source == PTSRC_ioapic);
-
-    if ( pt->vcpu == NULL )
-        return;
-
-    write_lock(&pt->vcpu->domain->arch.hvm.pl_time->pt_migrate);
-    pt->vcpu = v;
-    if ( pt->on_list )
-    {
-        list_del(&pt->list);
-        list_add(&pt->list, &v->arch.hvm.tm_list);
-        migrate_timer(&pt->timer, v->processor);
-    }
-    write_unlock(&pt->vcpu->domain->arch.hvm.pl_time->pt_migrate);
-}
-
-void pt_adjust_global_vcpu_target(struct vcpu *v)
-{
-    struct PITState *vpit;
-    struct pl_time *pl_time;
-    int i;
-
-    if ( !v || !has_vpit(v->domain) )
-        return;
-
-    vpit = &v->domain->arch.vpit;
-
-    spin_lock(&vpit->lock);
-    pt_adjust_vcpu(&vpit->pt0, v);
-    spin_unlock(&vpit->lock);
-
-    pl_time = v->domain->arch.hvm.pl_time;
-
-    spin_lock(&pl_time->vrtc.lock);
-    pt_adjust_vcpu(&pl_time->vrtc.pt, v);
-    spin_unlock(&pl_time->vrtc.lock);
-
-    write_lock(&pl_time->vhpet.lock);
-    for ( i = 0; i < HPET_TIMER_NUM; i++ )
-        pt_adjust_vcpu(&pl_time->vhpet.pt[i], v);
-    write_unlock(&pl_time->vhpet.lock);
-}
-
 static void pt_resume(struct periodic_time *pt)
 {
     struct vcpu *v;
@@ -566,14 +434,12 @@ static void pt_resume(struct periodic_time *pt)
         return;
 
     pt_lock(pt);
-    if ( pt->pending_intr_nr && !pt->on_list && inject_interrupt(pt) )
+    if ( pt->pending_intr_nr && inject_interrupt(pt) )
     {
         pt->pending_intr_nr--;
         cb = pt->cb;
         cb_priv = pt->priv;
         v = pt->vcpu;
-        pt->on_list = 1;
-        list_add(&pt->list, &pt->vcpu->arch.hvm.tm_list);
     }
     pt_unlock(pt);
 
diff --git a/xen/include/asm-x86/hvm/vcpu.h b/xen/include/asm-x86/hvm/vcpu.h
index 8adf4555c2a..9a756964fb0 100644
--- a/xen/include/asm-x86/hvm/vcpu.h
+++ b/xen/include/asm-x86/hvm/vcpu.h
@@ -148,9 +148,8 @@ struct hvm_vcpu {
     s64                 cache_tsc_offset;
     u64                 guest_time;
 
-    /* Lock and list for virtual platform timers. */
+    /* Lock for virtual platform timers. */
     spinlock_t          tm_lock;
-    struct list_head    tm_list;
 
     bool                flag_dr_dirty;
     bool                debug_state_latch;
diff --git a/xen/include/asm-x86/hvm/vpt.h b/xen/include/asm-x86/hvm/vpt.h
index 9440fe4ac7d..af04efa5e01 100644
--- a/xen/include/asm-x86/hvm/vpt.h
+++ b/xen/include/asm-x86/hvm/vpt.h
@@ -31,11 +31,7 @@
 typedef void time_cb(struct vcpu *v, void *opaque);
 
 struct periodic_time {
-    struct list_head list;
-    bool on_list;
     bool one_shot;
-    bool do_not_freeze;
-    bool irq_issued;
     bool warned_timeout_too_short;
     bool level;
 #define PTSRC_isa    1 /* ISA time source */
@@ -145,11 +141,9 @@ struct pl_time {    /* platform time */
     struct domain *domain;
 };
 
-void pt_save_timer(struct vcpu *v);
-void pt_restore_timer(struct vcpu *v);
-void pt_migrate(struct vcpu *v);
+void pt_freeze_time(struct vcpu *v);
+void pt_thaw_time(struct vcpu *v);
 
-void pt_adjust_global_vcpu_target(struct vcpu *v);
 #define pt_global_vcpu_target(d) \
     (is_hvm_domain(d) && (d)->arch.hvm.i8259_target ? \
      (d)->arch.hvm.i8259_target : \
@@ -158,7 +152,7 @@ void pt_adjust_global_vcpu_target(struct vcpu *v);
 void pt_may_unmask_irq(struct domain *d, struct periodic_time *vlapic_pt);
 
 /* Is given periodic timer active? */
-#define pt_active(pt) ((pt)->on_list || (pt)->pending_intr_nr)
+#define pt_active(pt) ((pt)->pending_intr_nr || timer_is_active(&(pt)->timer))
 
 /*
  * Create/destroy a periodic (or one-shot!) timer.
-- 
2.30.1


Re: [PATCH v3 10/11] x86/vpt: remove vPT timers per-vCPU lists

Posted by Jan Beulich 3 weeks, 3 days ago
On 31.03.2021 12:33, Roger Pau Monne wrote:
> No longer add vPT timers to lists on specific vCPUs, since there's no
> need anymore to check if timer interrupts have been injected on return
> to HVM guest.
> 
> Such change allows to get rid of virtual timers vCPU migration, and
> also cleanup some of the virtual timers fields that are no longer
> required.
> 
> The model is also slightly different now in that timers are not
> stopped when a vCPU is de-scheduled. Such timers will continue
> running, and when triggered the function will try to inject the
> corresponding interrupt to the guest (which might be different than
> the currently running one). Note that the timer triggering when the
> guest is no longer running can only happen once, as the timer callback
> will not reset the interrupt to fire again. Such resetting if required
> will be done by the EOI callback.
> 
> Since virtual timers are no longer added to per-VCPU lists when active
> a new 'masked' field is added to the structure, to signal whether a
> timer has it's interrupt source currently masked.

I guess this paragraph has become stale with ...

> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
> ---
> Changes since v2:
>  - Remove pt_{save/restore}_timer and instead use
>    pt_{freeze/thaw}_time.
>  - Remove the introduction of the 'masked' field, it's not needed.

... this change?

Other than this
Reviewed-by: Jan Beulich <jbeulich@suse.com>

>  - Rework pt_active to use timer_is_active.
> 
> Changes since v1:
>  - New in this version.
> ---
>  xen/arch/x86/domain.c          |   4 +-
>  xen/arch/x86/hvm/hvm.c         |   4 +-
>  xen/arch/x86/hvm/vlapic.c      |   1 -
>  xen/arch/x86/hvm/vpt.c         | 174 ++++-----------------------------
>  xen/include/asm-x86/hvm/vcpu.h |   3 +-
>  xen/include/asm-x86/hvm/vpt.h  |  12 +--
>  6 files changed, 27 insertions(+), 171 deletions(-)

Yet nicer than the previous one!

Jan