[patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe

2015-04-08 Thread Marcelo Tosatti 
Since lapic timer handler only wakes up a simple waitqueue,
it can be executed from hardirq context.

Also handle the case where hrtimer_start_expires fails due to -ETIME,
by injecting the interrupt to the guest immediately.

Reduces average cyclictest latency by 3us.

Signed-off-by: Marcelo Tosatti mtosa...@redhat.com

---
 arch/x86/kvm/lapic.c |   42 +++---
 1 file changed, 39 insertions(+), 3 deletions(-)

Index: rt-linux/arch/x86/kvm/lapic.c
===
--- rt-linux.orig/arch/x86/kvm/lapic.c  2015-04-08 20:20:41.0 -0300
+++ rt-linux/arch/x86/kvm/lapic.c   2015-04-08 20:21:16.592739674 -0300
@@ -1034,8 +1034,38 @@
   apic-divide_count);
 }
 
+
+static enum hrtimer_restart apic_timer_fn(struct hrtimer *data);
+
+static void apic_timer_expired(struct hrtimer *data)
+{
+   int ret, i = 0;
+   enum hrtimer_restart r;
+   struct kvm_timer *ktimer = container_of(data, struct kvm_timer, timer);
+
+   r = apic_timer_fn(data);
+
+   if (r == HRTIMER_RESTART) {
+   do {
+   ret = hrtimer_start_expires(data, HRTIMER_MODE_ABS);
+   if (ret == -ETIME)
+   hrtimer_add_expires_ns(ktimer-timer,
+   ktimer-period);
+   i++;
+   } while (ret == -ETIME  i  10);
+
+   if (ret == -ETIME) {
+   printk_once(KERN_ERR %s: failed to reprogram timer\n,
+  __func__);
+   WARN_ON_ONCE(1);
+   }
+   }
+}
+
+
 static void start_apic_timer(struct kvm_lapic *apic)
 {
+   int ret;
ktime_t now;
atomic_set(apic-lapic_timer.pending, 0);
 
@@ -1065,9 +1095,11 @@
}
}
 
-   hrtimer_start(apic-lapic_timer.timer,
+   ret = hrtimer_start(apic-lapic_timer.timer,
  ktime_add_ns(now, apic-lapic_timer.period),
  HRTIMER_MODE_ABS);
+   if (ret == -ETIME)
+   apic_timer_expired(apic-lapic_timer.timer);
 
apic_debug(%s: bus cycle is % PRId64 ns, now 0x%016
   PRIx64 , 
@@ -1097,8 +1129,10 @@
ns = (tscdeadline - guest_tsc) * 100ULL;
do_div(ns, this_tsc_khz);
}
-   hrtimer_start(apic-lapic_timer.timer,
+   ret = hrtimer_start(apic-lapic_timer.timer,
ktime_add_ns(now, ns), HRTIMER_MODE_ABS);
+   if (ret == -ETIME)
+   apic_timer_expired(apic-lapic_timer.timer);
 
local_irq_restore(flags);
}
@@ -1587,6 +1621,7 @@
hrtimer_init(apic-lapic_timer.timer, CLOCK_MONOTONIC,
 HRTIMER_MODE_ABS);
apic-lapic_timer.timer.function = apic_timer_fn;
+   apic-lapic_timer.timer.irqsafe = 1;
 
/*
 * APIC is created enabled. This will prevent kvm_lapic_set_base from
@@ -1707,7 +1742,8 @@
 
timer = vcpu-arch.apic-lapic_timer.timer;
if (hrtimer_cancel(timer))
-   hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
+   if (hrtimer_start_expires(timer, HRTIMER_MODE_ABS) == -ETIME)
+   apic_timer_expired(timer);
 }
 
 /*


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[patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe

2015-01-21 Thread Marcelo Tosatti 
Since lapic timer handler only wakes up a simple waitqueue,
it can be executed from hardirq context.

Also handle the case where hrtimer_start_expires fails due to -ETIME,
by injecting the interrupt to the guest immediately.

Reduces average cyclictest latency by 3us.

Signed-off-by: Marcelo Tosatti mtosa...@redhat.com

---
 arch/x86/kvm/lapic.c |   42 +++---
 1 file changed, 39 insertions(+), 3 deletions(-)

Index: linux-stable-rt/arch/x86/kvm/lapic.c
===
--- linux-stable-rt.orig/arch/x86/kvm/lapic.c   2014-11-25 14:14:38.636810068 
-0200
+++ linux-stable-rt/arch/x86/kvm/lapic.c2015-01-14 14:59:17.840251874 
-0200
@@ -1031,8 +1031,38 @@
   apic-divide_count);
 }
 
+
+static enum hrtimer_restart apic_timer_fn(struct hrtimer *data);
+
+static void apic_timer_expired(struct hrtimer *data)
+{
+   int ret, i = 0;
+   enum hrtimer_restart r;
+   struct kvm_timer *ktimer = container_of(data, struct kvm_timer, timer);
+
+   r = apic_timer_fn(data);
+
+   if (r == HRTIMER_RESTART) {
+   do {
+   ret = hrtimer_start_expires(data, HRTIMER_MODE_ABS);
+   if (ret == -ETIME)
+   hrtimer_add_expires_ns(ktimer-timer,
+   ktimer-period);
+   i++;
+   } while (ret == -ETIME  i  10);
+
+   if (ret == -ETIME) {
+   printk_once(KERN_ERR %s: failed to reprogram timer\n,
+  __func__);
+   WARN_ON_ONCE(1);
+   }
+   }
+}
+
+
 static void start_apic_timer(struct kvm_lapic *apic)
 {
+   int ret;
ktime_t now;
atomic_set(apic-lapic_timer.pending, 0);
 
@@ -1062,9 +1092,11 @@
}
}
 
-   hrtimer_start(apic-lapic_timer.timer,
+   ret = hrtimer_start(apic-lapic_timer.timer,
  ktime_add_ns(now, apic-lapic_timer.period),
  HRTIMER_MODE_ABS);
+   if (ret == -ETIME)
+   apic_timer_expired(apic-lapic_timer.timer);
 
apic_debug(%s: bus cycle is % PRId64 ns, now 0x%016
   PRIx64 , 
@@ -1094,8 +1126,10 @@
ns = (tscdeadline - guest_tsc) * 100ULL;
do_div(ns, this_tsc_khz);
}
-   hrtimer_start(apic-lapic_timer.timer,
+   ret = hrtimer_start(apic-lapic_timer.timer,
ktime_add_ns(now, ns), HRTIMER_MODE_ABS);
+   if (ret == -ETIME)
+   apic_timer_expired(apic-lapic_timer.timer);
 
local_irq_restore(flags);
}
@@ -1581,6 +1615,7 @@
hrtimer_init(apic-lapic_timer.timer, CLOCK_MONOTONIC,
 HRTIMER_MODE_ABS);
apic-lapic_timer.timer.function = apic_timer_fn;
+   apic-lapic_timer.timer.irqsafe = 1;
 
/*
 * APIC is created enabled. This will prevent kvm_lapic_set_base from
@@ -1699,7 +1734,8 @@
 
timer = vcpu-arch.apic-lapic_timer.timer;
if (hrtimer_cancel(timer))
-   hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
+   if (hrtimer_start_expires(timer, HRTIMER_MODE_ABS) == -ETIME)
+   apic_timer_expired(timer);
 }
 
 /*


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[patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe

2015-01-14 Thread Marcelo Tosatti 
Since lapic timer handler only wakes up a simple waitqueue,
it can be executed from hardirq context.

Reduces average cyclictest latency by 3us.

Signed-off-by: Marcelo Tosatti mtosa...@redhat.com

---
 arch/x86/kvm/lapic.c |   42 +++---
 1 file changed, 39 insertions(+), 3 deletions(-)

Index: linux-stable-rt/arch/x86/kvm/lapic.c
===
--- linux-stable-rt.orig/arch/x86/kvm/lapic.c   2014-11-25 14:14:38.636810068 
-0200
+++ linux-stable-rt/arch/x86/kvm/lapic.c2015-01-14 14:59:17.840251874 
-0200
@@ -1031,8 +1031,38 @@
   apic-divide_count);
 }
 
+
+static enum hrtimer_restart apic_timer_fn(struct hrtimer *data);
+
+static void apic_timer_expired(struct hrtimer *data)
+{
+   int ret, i = 0;
+   enum hrtimer_restart r;
+   struct kvm_timer *ktimer = container_of(data, struct kvm_timer, timer);
+
+   r = apic_timer_fn(data);
+
+   if (r == HRTIMER_RESTART) {
+   do {
+   ret = hrtimer_start_expires(data, HRTIMER_MODE_ABS);
+   if (ret == -ETIME)
+   hrtimer_add_expires_ns(ktimer-timer,
+   ktimer-period);
+   i++;
+   } while (ret == -ETIME  i  10);
+
+   if (ret == -ETIME) {
+   printk_once(KERN_ERR %s: failed to reprogram timer\n,
+  __func__);
+   WARN_ON_ONCE(1);
+   }
+   }
+}
+
+
 static void start_apic_timer(struct kvm_lapic *apic)
 {
+   int ret;
ktime_t now;
atomic_set(apic-lapic_timer.pending, 0);
 
@@ -1062,9 +1092,11 @@
}
}
 
-   hrtimer_start(apic-lapic_timer.timer,
+   ret = hrtimer_start(apic-lapic_timer.timer,
  ktime_add_ns(now, apic-lapic_timer.period),
  HRTIMER_MODE_ABS);
+   if (ret == -ETIME)
+   apic_timer_expired(apic-lapic_timer.timer);
 
apic_debug(%s: bus cycle is % PRId64 ns, now 0x%016
   PRIx64 , 
@@ -1094,8 +1126,10 @@
ns = (tscdeadline - guest_tsc) * 100ULL;
do_div(ns, this_tsc_khz);
}
-   hrtimer_start(apic-lapic_timer.timer,
+   ret = hrtimer_start(apic-lapic_timer.timer,
ktime_add_ns(now, ns), HRTIMER_MODE_ABS);
+   if (ret == -ETIME)
+   apic_timer_expired(apic-lapic_timer.timer);
 
local_irq_restore(flags);
}
@@ -1581,6 +1615,7 @@
hrtimer_init(apic-lapic_timer.timer, CLOCK_MONOTONIC,
 HRTIMER_MODE_ABS);
apic-lapic_timer.timer.function = apic_timer_fn;
+   apic-lapic_timer.timer.irqsafe = 1;
 
/*
 * APIC is created enabled. This will prevent kvm_lapic_set_base from
@@ -1699,7 +1734,8 @@
 
timer = vcpu-arch.apic-lapic_timer.timer;
if (hrtimer_cancel(timer))
-   hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
+   if (hrtimer_start_expires(timer, HRTIMER_MODE_ABS) == -ETIME)
+   apic_timer_expired(timer);
 }
 
 /*


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Re: [patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe

2015-01-14 Thread Rik van Riel 
On 01/14/2015 12:12 PM, Marcelo Tosatti wrote:
 Since lapic timer handler only wakes up a simple waitqueue,
 it can be executed from hardirq context.
 
 Reduces average cyclictest latency by 3us.
 
 Signed-off-by: Marcelo Tosatti mtosa...@redhat.com

Acked-by: Rik van Riel r...@redhat.com

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Re: [patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe

2014-12-05 Thread Marcelo Tosatti 
On Thu, Dec 04, 2014 at 02:53:26PM +0100, Paolo Bonzini wrote:
 
 
 On 25/11/2014 21:24, Thomas Gleixner wrote:
  On Tue, 25 Nov 2014, Rik van Riel wrote:
  On 11/25/2014 12:21 PM, Marcelo Tosatti wrote:
  Since lapic timer handler only wakes up a simple waitqueue,
  it can be executed from hardirq context.
 
  Reduces average cyclictest latency by 3us.
 
  Can this patch be merged in the KVM tree, and go
  upstream via Paolo?
  
  Not really as it has RT dependencies 
 
 Can hrtimer_start_expires even return ETIME on a non-RT kernel?  If yes,
 I can take patch 2.  If not, it's better to keep both patches in the RT
 tree.
 
 Paolo

It can't. We're still evaluating the necessity of this patch, will
resubmit accordingly.

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Re: [patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe

2014-12-04 Thread Marcelo Tosatti 
On Tue, Nov 25, 2014 at 06:38:04PM +0100, Paolo Bonzini wrote:
 
 
 On 25/11/2014 18:21, Marcelo Tosatti wrote:
  +
  +   if (r == HRTIMER_RESTART) {
  +   do {
  +   ret = hrtimer_start_expires(data, HRTIMER_MODE_ABS);
  +   if (ret == -ETIME)
  +   hrtimer_add_expires_ns(ktimer-timer,
  +   ktimer-period);
 
 Is it possible to just compute the time where the next interrupt
 happens?  

Yes but there is no guarantee hrtimer_start_expires will not fail.

 I suspect the printk and WARN_ON below can be easily triggered
 by a guest.

I'll remove those, thanks.


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Re: [patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe

2014-12-04 Thread Paolo Bonzini 


On 25/11/2014 21:24, Thomas Gleixner wrote:
 On Tue, 25 Nov 2014, Rik van Riel wrote:
 On 11/25/2014 12:21 PM, Marcelo Tosatti wrote:
 Since lapic timer handler only wakes up a simple waitqueue,
 it can be executed from hardirq context.

 Reduces average cyclictest latency by 3us.

 Can this patch be merged in the KVM tree, and go
 upstream via Paolo?
 
 Not really as it has RT dependencies 

Can hrtimer_start_expires even return ETIME on a non-RT kernel?  If yes,
I can take patch 2.  If not, it's better to keep both patches in the RT
tree.

Paolo
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[patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe

2014-11-25 Thread Marcelo Tosatti 
Since lapic timer handler only wakes up a simple waitqueue,
it can be executed from hardirq context.

Reduces average cyclictest latency by 3us.

Signed-off-by: Marcelo Tosatti mtosa...@redhat.com

---
 arch/x86/kvm/lapic.c |   42 +++---
 1 file changed, 39 insertions(+), 3 deletions(-)

Index: linux-stable-rt/arch/x86/kvm/lapic.c
===
--- linux-stable-rt.orig/arch/x86/kvm/lapic.c   2014-11-25 14:14:38.636810068 
-0200
+++ linux-stable-rt/arch/x86/kvm/lapic.c2014-11-25 14:17:28.850567059 
-0200
@@ -1031,8 +1031,38 @@
   apic-divide_count);
 }
 
+
+static enum hrtimer_restart apic_timer_fn(struct hrtimer *data);
+
+static void apic_timer_expired(struct hrtimer *data)
+{
+   int ret, i = 0;
+   enum hrtimer_restart r;
+   struct kvm_timer *ktimer = container_of(data, struct kvm_timer, timer);
+
+   r = apic_timer_fn(data);
+
+   if (r == HRTIMER_RESTART) {
+   do {
+   ret = hrtimer_start_expires(data, HRTIMER_MODE_ABS);
+   if (ret == -ETIME)
+   hrtimer_add_expires_ns(ktimer-timer,
+   ktimer-period);
+   i++;
+   } while (ret == -ETIME  i  10);
+
+   if (ret == -ETIME) {
+   printk(KERN_ERR %s: failed to reprogram timer\n,
+  __func__);
+   WARN_ON(1);
+   }
+   }
+}
+
+
 static void start_apic_timer(struct kvm_lapic *apic)
 {
+   int ret;
ktime_t now;
atomic_set(apic-lapic_timer.pending, 0);
 
@@ -1062,9 +1092,11 @@
}
}
 
-   hrtimer_start(apic-lapic_timer.timer,
+   ret = hrtimer_start(apic-lapic_timer.timer,
  ktime_add_ns(now, apic-lapic_timer.period),
  HRTIMER_MODE_ABS);
+   if (ret == -ETIME)
+   apic_timer_expired(apic-lapic_timer.timer);
 
apic_debug(%s: bus cycle is % PRId64 ns, now 0x%016
   PRIx64 , 
@@ -1094,8 +1126,10 @@
ns = (tscdeadline - guest_tsc) * 100ULL;
do_div(ns, this_tsc_khz);
}
-   hrtimer_start(apic-lapic_timer.timer,
+   ret = hrtimer_start(apic-lapic_timer.timer,
ktime_add_ns(now, ns), HRTIMER_MODE_ABS);
+   if (ret == -ETIME)
+   apic_timer_expired(apic-lapic_timer.timer);
 
local_irq_restore(flags);
}
@@ -1581,6 +1615,7 @@
hrtimer_init(apic-lapic_timer.timer, CLOCK_MONOTONIC,
 HRTIMER_MODE_ABS);
apic-lapic_timer.timer.function = apic_timer_fn;
+   apic-lapic_timer.timer.irqsafe = 1;
 
/*
 * APIC is created enabled. This will prevent kvm_lapic_set_base from
@@ -1699,7 +1734,8 @@
 
timer = vcpu-arch.apic-lapic_timer.timer;
if (hrtimer_cancel(timer))
-   hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
+   if (hrtimer_start_expires(timer, HRTIMER_MODE_ABS) == -ETIME)
+   apic_timer_expired(timer);
 }
 
 /*


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Re: [patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe

2014-11-25 Thread Paolo Bonzini 


On 25/11/2014 18:21, Marcelo Tosatti wrote:
 +
 + if (r == HRTIMER_RESTART) {
 + do {
 + ret = hrtimer_start_expires(data, HRTIMER_MODE_ABS);
 + if (ret == -ETIME)
 + hrtimer_add_expires_ns(ktimer-timer,
 + ktimer-period);

Is it possible to just compute the time where the next interrupt
happens?  I suspect the printk and WARN_ON below can be easily triggered
by a guest.

Paolo

 + i++;
 + } while (ret == -ETIME  i  10);
 +
 + if (ret == -ETIME) {
 + printk(KERN_ERR %s: failed to reprogram timer\n,
 +__func__);
 + WARN_ON(1);
 + }
 + }
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Re: [patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe

2014-11-25 Thread Jan Kiszka 
On 2014-11-25 18:38, Paolo Bonzini wrote:
 
 
 On 25/11/2014 18:21, Marcelo Tosatti wrote:
 +
 +if (r == HRTIMER_RESTART) {
 +do {
 +ret = hrtimer_start_expires(data, HRTIMER_MODE_ABS);
 +if (ret == -ETIME)
 +hrtimer_add_expires_ns(ktimer-timer,
 +ktimer-period);
 
 Is it possible to just compute the time where the next interrupt
 happens?  I suspect the printk and WARN_ON below can be easily triggered
 by a guest.

We have a lower bound for the period that a guest can program. Unless
that value is set too low, this should practically not happen if we
avoid disturbances while handling the event and reprogramming the next
one (irqs off?).

Jan

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Re: [patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe

2014-11-25 Thread Rik van Riel 
On 11/25/2014 12:21 PM, Marcelo Tosatti wrote:
 Since lapic timer handler only wakes up a simple waitqueue,
 it can be executed from hardirq context.
 
 Reduces average cyclictest latency by 3us.

Can this patch be merged in the KVM tree, and go
upstream via Paolo?

 Signed-off-by: Marcelo Tosatti mtosa...@redhat.com

Acked-by: Rik van Riel r...@redhat.com

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Re: [patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe

2014-11-25 Thread Thomas Gleixner 
On Tue, 25 Nov 2014, Rik van Riel wrote:
 On 11/25/2014 12:21 PM, Marcelo Tosatti wrote:
  Since lapic timer handler only wakes up a simple waitqueue,
  it can be executed from hardirq context.
  
  Reduces average cyclictest latency by 3us.
 
 Can this patch be merged in the KVM tree, and go
 upstream via Paolo?

Not really as it has RT dependencies 

Thanks,

tglx
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